Lt1 high idle symptoms chevy. around 1500 and after a minute or two it raises up to 1800.

Lt1 high idle symptoms chevy The car was running fine yesterday. I replaced the idle air valve and has run fine since then. He had a 94/95 LT1 that he reprogrammed. I think I saved the data log from the scan program, but Ill have to check. once i got back up to speed again the oil must have cooled down, oil pressure went back to the normal 20+ PSI i usually get on fully warmed up engine. Replaced it with the LT4 fuel pump and just last week the car started Apr 25, 2009 · But people are forgetting that a pressure regulator can fail without fuel leakage. Disconnect the battery and remove the IAC. Feb 21, 2015 · Will a bad idle air control valve cause the car to shut off when idling? How about the tps would that cause this. I hooked up a gauge and got 40ish at prime and idle but the pressure would drop to ~20 close to readline. Thanks bud, it's a 88 Chevy van with a 350. If it isn't surging at idle, the idle will still be very rough and the car shakes a bit. I was chasing a ghost. May 10, 2014 · And no matter what, the rpms never drop like they should. Still 1995 Caprice wagon 5. Just a little rich at full throttle. I'll check the seating of the elbow and throttle body, the seal is not great, not as good as the factory original. Jul 15, 2008 · It sounds pretty good at idle. A lot of LT1's have a slightly skippy idle, then smooth out as soon as it goes beyond 1000 or 1100 rpm. The car ran perfectly fine when I parked it. I'm going to get the Opti troubleshooting info from SHBOX and running with that soon. An EGR valve that won't close when it is supposed to will cause rough idle and/or engine dies. Shortly after, I find my idle now is running about 1600-1700 RPM - for no Nov 22, 2007 · thats a good thing to know cause all i have prior to this car is knowledge of fords. They get jealous of each other I swear! The problem I am having is a very loud single gunshot style back fire only at idle. TBI, you can jump the OBD port or get a CodeMate and put the ECM in service mode - you got blink codes - 12 and nothing else. Jul 16, 2018 · If LT1 you need the tech mate tool or laptop to set the idle. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright May 15, 2018 · Hi all. At the end it would seem to just shut off, but would catch and run fine again for short periods. Aug 6, 2019 · Faulty Mass Airflow Sensor Symptoms: Chevy Camaro. it stopped doing the high idle thing but began up-ticking and down-ticking engine RPM about 200 RPM or so when hot, but not Jan 27, 2008 · The scanner will show you the number of steps or "counts" that the motor has opened the idle air passage. 10 gears, SFC,lower control arms,adjustable panhard bar,adjustable torque arm, rear sway bar, 3-1/2 inch drive shaft with Ds loop and poly bushings,finally got traction with new nitto drag radial extremes,410 rwhp 385 Feb 27, 2024 · On a cammed lt1 using the 8051 ecm, and running headers set the individual fueling values to 1 in both idle and off idle. I can't feel a miss but can still hear the exhaust make a slight "pop" occasionally at idle. 1992 Chevrolet Corvette LT1 idling at 2000 rpm in park and neutral, 211,000, LT1 350, Yes, new Idle air control valve Mechanic's Assistant chat Customer: 1992 Chevrolet Corvette LT1 idling at 2000 rpm in park and neutral Mechanic's Assistant: How many miles are on the Chevrolet? Feb 25, 2007 · And a High resolution, when the cam gear rotates 1 full time. When I got the new flywheel there was what looked like a weight in the box but when I looked at the flywheel I didn't see anywhere to install it. Mar 29, 2014 · The idle is always at 1000rpm, no lower. Apr 21, 2010 · This is from the 1994 GM Factory Serive Manual, Book 2: IDLE AIR CONTROL (IAC) VALVE Remove or Disconnect 1. Should be same for Impala SS, Camaro, Trans Am, Corvette although each intake set-up is Apr 18, 2024 · In summary, these three things fixed the high idle and RPM hang (once confirmed no vacuum leaks): 1. This allows the factory system to turn on the cold advance and high idle solenoids when the motor is cold (assuming that system is working), and when you provide your own 12v to the high idle solenoid, the diode will block it from reaching the cold advance. I know that the IAC is working because if it stumbles below 600 it will push up to 600, and when it is cold it will idle up to 800-1000 RPM until warm. would have pulsed 360 times. Bored . 020 over speed pro pistons,comp custom cam,comp push rods,comp 1. I have a shaking at idle and a significant vibration at high rpm. Mar 25, 2003 · DTC P0507 Idle Speed High Circuit Description The Idle Air Control valve is a PCM controlled stepper motor located on the throttle body. Sep 18, 2012 · Sounds like oil is getting past the valve guide oil seals, leaking down into the cylinder or cylinders, and burning. The car was running lean for a long time and would pop and miss wayyyyyyy bad at high rpm at wot. 05-0. By ReidB in forum GM EFI Systems Replies: 27 Nov 13, 2012 · IAT: only reached a high of 19°C after sitting for a few minutes LTFT: 25% both sides Front O2 sensors, both sides: 0. You're commenting like TBIremember, that TBI unit is from the Chevy 454 and not chevy 350. Replaced the pump, and pressure was good to go again. Remove the entire throttle body and clean it. i owned 6 diff. When the mass airflow sensor has gone bad, you’ll definitely feel it. it idles around 1500 to 1800 rpm and it is tearing the transmission apart. 6 spd. Clean throttle body and replace all 3 gaskets. The AFGS should be around 6-10 and the IAC counts somewhere in the 5-50 range (I usually see closer to 40 - 50) at a normal idle of around 700rpm, yours will be higher with yours set to 1100rpm (as questioned by bobdec, this is not normal nor ideal for Feb 3, 2012 · Pressure on a '94 engine setup s/b high 30's at idle and vacuum to the FP regulator, then pull the vacuum line (simulates lo/no vac @ WOT) and pressure should rise about 5 lbs. when driving the car it runs fine but at idle it revs up and down till it stalls. 1995 Impala SS LT1 383 Stroker Daily Driver Jun 26, 2004 · C4 Tech/Performance - 92 LT1 - High Idle after IAC Replacement - I was experiencing a high idle (2,000 rpm) after the car was driven for a bit. If it is original, it is likely burned up and is grounding on the block causing your stumbling issues. Jul 2, 2010 · Like I mentioned, the car has had the TB removed and cleaned (twice actually) along with a new IAC, new TPS, new 02 sensors, new injectors (Bosch III/FIC), new PCV, new air and fuel filters, shows 40 psi of fuel pressure at idle and 43 - 45 under load, and holds a steady 17" of vacuum at idle. Myersfw, tried that, no joy. Aug 18, 2003 · C4 Tech/Performance - LT1 stumbles under high load - My '95 LT1 stumbles under high load (full throttle) usually in the 4600 to 5500 rpm range. Sep 4, 2011 · Car starts with NO issues and drops idle to about 800-1000 rpm (cold start) quickly. The most common failures would be carbon buildup keeping it from closing or a leak in the vacuum line or diaphram keeping it from opening. yet i still have an extream high idle problem, any sujestions Sep 15, 2009 · Just a little lt1. if i step on the gas it comes back to idle at almost 2000rpm. Idle air control sensor. The PCM will adjust the IAC position for the programmed idle speed (this may take a couple of minutes, the engine may idle low or high initially, and the engine may surge. Dec 5, 2016 · Vince Driven a lot! My '74 Stingray, not driven so much now. Electrical connector from IAC valve. 3. 64V with the throttle blades closed. Along with new Plugs, Wires, and Opti. If i plug the hole with my thumb where the IAC is the car will idle at 900 rpm. 000 KM Yesterday without any reason when I was arriving in my home driveway my car begin to have a very rough idle/low RPM like if I have misfire on a cylinder, but if I increase the throttle the problem is barely visible. I have repalced the fuel pump and Mar 1, 2018 · Of course as soon as I buy my LS1 camaro my LT1 starts acting up. drive train issues can cause misfire type symptoms, pop your valve covers off and inspect what you can (springs most common). Is there an acceptable way of increasing the idle rpm slightly without computer mods? 5. Basically when starting the car up, you can hear the car wanting to hestitate a little at idle. I'd have to study the EVAP system, but it's POSSIBLE that at ~200*F a vacuum solinoid opens and the hose it's opening to has a leak, causeing a vacuum leak and a poor idle. Check Engine Light comes on Jun 9, 2016 · C4 Tech/Performance - 95 LT1 Rough Idle - Hello all. This caused the idle to be a little uneven, and often too high. Feb 4, 2010 · Back-probed the Throttle Position Sensor at idle . ported & polished heads, long tube headers. Your right side has an issue with the fuel trims. In this video I discuss the symptoms of a failed high pressure fuel pump. Clutch is original but the high idle is Nov 25, 2008 · This just started a couple of days ago. This Apr 10, 2015 · Can you find a file sharing sight and post a datamaster log of just the idle. If the idle is too high (compared to the idle speed programmed in the PCM) , the PCM will try and close the IAC passage, by dropping the IAC counts. Jul 28, 2015 · 97 trans am ws6 with only 25k on it, your typical heads and comp cam port and polished intake, pace setter long tubes, borla catbac, 58mm TB 32lb injectors, moser ford 9" with 4. I first checked for vacuum Customer: My 1994 Z28 LT1, 55,000 miles had a Idle problem last year 2-20-08 intermitant jump in RPM from mormal 750 rpm up to about 2000 rpm. After driving the car for around 20 to 30 minutes and at a full stop (normal cruise is fine) the engine idle suddenly surges to the point that I really have to hold down the brake to keep the car from moving forward. The small dealership where I bought it put in new plugs and he said it made it run a bit better but back then they car needed a fuel pump that I put in so maybe the plugs are bad now. I have to really hit the brakes to stop it. ) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily! Apr 12, 2013 · In my experience, bad ignition coils have shown up as misfiring at high rpm, high load conditions. Its bolted to the throttle body. Aug 29, 2019 · LT1 Throttle body IAC, TPS sensor replacement on a 1996 Caprice 9C1. I replaced the IAC. Intake Air Temp sensor, unplugged displayed -40C and with the connector jumpered 304C. As soon as I switched throttle bodies and kept the blades closed at idle, the idle went down and stayed steady. Started off week with car running really bad. That is the beauty of those years. Basic car maintenance, the plug wires and the coil have to be changed periodically. IAC Jul 18, 2024 · If the idle air control valve did not compensate for these, the idle speed would drop when certain accessories are used. 5 x-pipe with dynomax bullets,march underdrive pulleys,gm opti,msd cap and rotor,Msd 6AL,Moore 10mm race wires,SLP line lock,SLP fan switch,aluminum D/S,Built 4l60e,TCI 3,000 stall,B Feb 19, 2009 · An engine is like an air compressor. thank you Bill Sep 3, 2020 · The car also has some issues starting it usually will crank for 5 seconds or longer before turning over. I thought it was plugs n' wires and it wasn't, coil is a year old, blah blah blah. ) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily! Jul 19, 2017 · TPS is at . TPS Voltage is set to . Nov 28, 2007 · As it is now, it runs like a striped ass ape, and shifts about 6 grand wot, its just that damned high idle. Otherwise all operate within spec. I go to start it the next day, and it won't idle. Incorrect idle speed: An IAC valve that sticks in the closed position will create an idle speed that’s too low. 1:1 Ratio Short-Throw Shifter, ZL1 Pedals, ZL1 splash guards, NPP Dual-mode quad tip exhaust, Z28 strut tower brace, Camaro LED Cup-holders with footwell Lighting option, Leather visors, and Leather E-brake boot. I have been fiddling with it over the past few weekends but I cant seem to narrow down the problem. Sep 28, 2011 · How to reset the idle speed: Depress accelerator slightly Start engine, then release accelerator pedal, run engine for 5 seconds Turn ignition "OFF" for ten seconds Restart engine and check for proper idle operation. Was worse in traffic with high underhood temperatures. the oil pressure dropped enough to trigger the check gauges light. AL6 MSD. I've had drivability problems intermittently, and it seems to be caused by high fuel pressure at cruise and idle. Questions about cruzing/idle fuel pressure. The idle air control valve is most important on a cold startup. Reset IAC. Apr 16, 2003 · C4 Tech/Performance - Correct idle speed, LT1 - Can someone tell me what the correct idle speed is for an LT1? Mine is a 95 LT1, 6M. Nov 3, 2016 · The LS1 were a small improvement over the 235000 mile LT1 Injectors. Plug hole in throttle body butterfly valve. Apr 20, 2012 · C4 Tech/Performance - IAC Gone Bad? Symptoms? Rough Idle and hesitationPLEASE HELP! - Hello allI posted a new thread last week with not much help in replies and hoping to get a little more this time. Is this normal idle rpm? 2. I don't know when things like the IAC, TB or MAF were cleaned, I'm searching for those answers now. clogged injectors, plugs, plug wires, coil packs, weak fuel pump, vacuum leak, bad head gasket between cylinders can all cause misfire or misfire type symptoms. Roughly a month ago it began to misfire every so often. ) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily! Nov 18, 2012 · Initially the flashing SES would be rectified with a slight increase RPM and would stay away until low RPMs were introduced via idle or high gear/low speed, that is not the case anymore, it flashes at all RPMs, however, the performance is NO different, the idle is NO different, it starts NO different. Recently he has noticed it will hesitate and almost die, under really light acceleration, like up a hill or the driveway. Guys, I want to run the symptoms by you, and see if we are thinking the same thing here. It does not matter how high I set it with the laptop, it still starts to surge after sitting in idle for a bit. scanner showed a bad tps sensor & I replaced it . Your RPMs will drop way down the car may feel like it’s about to stall. The car is a 96 TA that I rebuilt about 2 years ago. 03 raptor that'll pull your arms out of their sockets 97 WS6 Firebird (full drivetrain swap), edelbrock headers and full exhaust, custom pcm tune, throttle body coolant bypass, b&m shift kit, lt4 hot cam, bald tires. Jan 23, 2011 · Hey all. 9 V, fluctuating as expected Rear O2 sensors, both sides: 0. A faulty idle air control (IAC) valve can cause a number of problems with your vehicle: 1. EGR at idle should be closed and not letting any exhaust into intake at idle. So i think the IAC needs replacing although i cleaned it the idle remained the same. ^^ 04-03-2019, 12:35 PM Nov 19, 2008 · 1995 z28 , abs 16" trans am rims , m6 , slp springs , k&n homemade cai ,3 inch exhaust,4. Feb 26, 2008 · I bought a 1990 Chevy 1500 pickup several months back. The symptoms of this fault code may include a high idle speed or fluctuating idle speed. Since it only happens when your parked on a hill, I would say, depending on weather your car is facing up the hill or down the hill, either the front or rear guides are submerged in oil and are leaking. 67 volts at idle. Porting the intake, adding a larger throttle body and runners, and higher flow injectors will help a high performance engine. I removed the throttle body and i cleaned it. 80) when the throttle was snapped shut at speed May 2, 2008 · When my pump went bad, the symptom was a high-end stumble around 5000rpm. Here are the most common symptoms of a bad or failing MAF sensor: Idle Issues– Your Camaro may run rich or lean when idling, or it may also idle erratically. Oct 12, 2012 · Still can't find why high idle in park only about 1800 - 2000 rpms. Apr 21, 2009 · 94 Z28: 383 12. Now the idle has speed is up to 1500 to 2000 rpm and once in a while returns to normal speed. Problems with the idle air control will be most obvious during this time. I took my throttle body off took the iac sensor off and probed it. Apr 4, 2016 · 2014 2SS/RS, Z28 CAI and High Wing Spoiler, ZL1 5. The ECM on the 1996 S10 will no work on the LT1 engine, for one thing the S10 ECM will only command for 6 fuel injectors and will have different injection pulse and so on. it ran smooth about 7 min then service lite come on & high idle started, even AC stopped blowing cold any help appreciate it. Adjust idle set screw as necessary. Sep 16, 2013 · "high idle" is around 15-1800rpm. If at all possible start log when just started up and cold (in open loop) and let it idle for at least 5-10 mins to enter closed loop and then get up to 180* F (about 80*C) . found here: 4th Gen LT1 F-Body Tech Aids Says LTI but the procedure should be the same Sep 19, 2021 · I've personally had rough idle leading to stalling problems on LT1 cars from 3 common things: (1) IAC stuck, (2) Opti issues, but commonly moisture due to clogged vent harness, (3) random low fuel pressure due to weak or failing pump. STOP SUPPORTING THEIVES. now this being my daily driver I had to keep driving it and it ran ok for a while until the check engine light came on so I took it to auto zone to get it scanned and it gave me a p0300 code multiply misfire and a p0171 code so Apr 2, 2014 · 110k, Bright Red, Hard top, Moroso cold air, Trick flow ceramic intake elbow, SLP 3" Y pipe, Random tech high flow cat, Borla adjustable cat back with DHM cutout, MSD 8. Feb 15, 2016 · My in gear idle is 700RPM, out of gear 900-1000RPM now. Didn't surge when shifting into gear Came home and shifted into P, then the idle speed increased to 1300RPM Yup, look no further, the IAC is bad or at least dirty. 418 crank HP. What am I missing? Aug 31, 2012 · I have a 1995 Trans am with a built LT1 6speed. Nov 23, 2013 · 1. LT1 High Idle. There is also a lean popping noise in the exhaust (light backfire). Dec 14, 2010 · C4 Tech/Performance - Help me with my LT1 high idle, out of ideas - Back story: I bought a 92 in July and have been slowly bringing it back to working order. Oct 2, 2011 · My 1995 Camaro LT1/T56 combo transplant in a 1984 Jaguar xj6 is suffering from high idle. Jan 2, 2012 · Now she idles at 850-875 with a target of 800. Idle speed warm should be 800 rpm, even after just a minute of running. Jan 19, 2012 · The issue I'm having is the idle sticking around 2000 rpm's when I let off the gas. Engine cold: Idle: 40psi Driving: 40psi at idle that increases to about 70 psi at 6000rpms. Please help me out give me some suggestions please. So i supose air leaks are easy here. Nov 17, 2004 · LT1; Auto; Save Share 1992 Chevy S10, 3. I replace the MAF 2 months ago and it went away but now its back. My car started idling high and is now idling at 2000 rpm. it was a 2 Dec 10, 2024 · I swapped out my blown LT1 (T56 swapped) for another one and decided to replace the clutch and flywheel at the same time. 1. The stepper motor drives a valve pintle which protrudes into a passage that bypasses the throttle plates. etc, etc. 4L Turbo auto 3GNCJPSB8GL142716 Save Share Reply Quote Like Oct 31, 2012 · The PCM will accept TPS voltages from . With a longer hose taped to windshield you could verify FP under driving load conditions. I also disconnected the IAC valve, and none of the symptoms changed either way other than the idle stayed at 2k rpm. To decrease idle speed, the PCM commands the IAC valve pintle to extend. Starts right up but wont hold a idle have to keep light pressure on the pedal for it to stay running. I changed out the old rusty IAC valve motor and cars running good. 5vdc. DONT BUY HONDUH. Mostly noticeable in 5th and 6th at low RPM with a high load. 1L V6 5 speed. A rich condition is when there is not enough air relative to Feb 26, 2016 · 2010 Cobalt LS, 2. Any advice on getting it to Dec 10, 2005 · My '37 Plymouth coupe runs a '94 'Vette 350 ci LT1/R400 using a Street & Performance harness. Run them on the Impala SS with a success. Is there anyway to adjust the shift points? 6. 3 - . 6. I put new gaskets and a new TPS LT1 Normal Oil Pressure Range V8 LT1 Engine, Exhaust, and Bolt-Ons Idle pressure does not need to be very high. Pretty much what your problem is on why DTC 16 is setting is that your opti's high resolution has made 2 full rotations or more without the low resolution signal pulsing so you low resolution side is all out of wack. Aug 9, 2005 · Chevy used OBDII hardware on the 94 and 95 LT1's. you would hear lifter tick. Oct 20, 2024 · The ‘92 Vette LT1 Manual Transmission runs well and occasionally has problems with high idle, running at 1500, sometimes close to 2000rpm. MAP value, and another cross referenced table I can't remember at the moment. thank you Bill Aug 6, 2019 · '95 Stock Lt1 with 67,000 miles. Followed the forum's advice and replaced the IAC, cleaned the throttle body and set IAC according to the manual. All other engine performance is normal. Does anyone know if the "adjustable throttle Aug 10, 2009 · An EGR valve that won't open when it is supposed to will cause high NOx emissions. Stock bottom 350, Built by B-Body Performance NA: 10. Dec 12, 2021 · In this video, you will learn 4 symptoms of a bad idle air control valve. :thumbsup:. around 1500 and after a minute or two it raises up to 1800. When taking it Apr 2, 2007 · opti-spark is lovingly referred to as ''opti-crap'' by many techsalso a 100k expiration piece''might'' be your prob based on symptoms reportedonly good test is to try a known good oneas an lt1 owner (my 94 buick roaddie has a vette lt1 engine) i keep a spare ''good used'' opti on hand and do loan it out if you want to leave a Jan 9, 2019 · Drives 2016 Sunset Orange Trax LT1 1. mustangs from high school till bout a year ago and then i became partial to the gm side of life ofter drivin my boys 10 second ram air. Problem went away on its on - believe it was bad gas (probably water in fuel) that was resolved when new gas mixed in. Jan 8, 2016 · The idle air control valve is programmed to regulate and maintain the engine idle speed at a constant rate. To get my idle to go back down to normal, I have to shoot a quick rev where I take my foot of the This Is For A 1996 Chevy Caprice (cop) Lt1. I have ZERO driveability symptoms except the idle. If the EGR is stuck open at idle, exhaust gas will be entering intake and causing idle stumble, stalling, low RPM issues. For example, if you're experiencing noise coming from the top end of the engine, or Mar 25, 2005 · 4) Adjust the screw in the throttle body until the idle speed drops to ~500rpm 5) Turn off the engine 6) Reconnect the IAC harness 7) Restart the engine and let idle. 9 volts as being 0% throttle, with the ideal voltage being . This is to prevent over-stressing the core at high engine rpms. They gradually drop, unless it is stumbling. Here's a handy search engine for searching salvage yards for the parts you need. But, just as a high- flowing carburetor can be too big for a mild to stock engine, so can the fuel injection. So if you know me from other LT1 forums, you probably already know the scoop, but if not, here's the problem: I had a 2+ cylinder misfire in my LT1 in a 1995 Z28 A4. Dec 15, 2010 · I've been chasing the same symptoms for the better part of 6 months now. Would changing the rockers require me to have the PCM recalibrated? 4. For what I’ve been hearing, this is a common problem on the LT1 V-8s from 1992-1994. Plug wires lying on hot exhaust manifolds will shorten their life and cause high voltage loads on the entire ignition system. No Leaks because were checked a thousand times. I also did the trap door method. Now if you are sitting in idle, no airflow, that is what the coolant temp will get to before fans are commanded on, roughly about 3/4 up on the temp gauge, give or take. 5vdc and also at WOT 4. Apr 9, 2014 · about a month ago I noticed when I was driving my car was having a surge like I was feathering the gas while driving. Customer: My 1994 Z28 LT1, 55,000 miles had a Idle problem last year 2-20-08 intermitant jump in RPM from mormal 750 rpm up to about 2000 rpm. Mar 17, 2016 · C7 Tech/Performance - High Pressure Fuel Pump Failure #2 - Soback in December my car starting making a terrible vibration type noise from under the intake manifold and it turned out being the stock LT1 high pressure fuel pump that took a sh!t. So I pulled it into the garage. It does a little better with a load on it in gear but still isn't right- jerks and what not. Replace IAC. Pulled vacuum hoses, the only one that increased the idle was the small hose connected to the throttle body on the passenger side. I noticed that when my throttle sticks which is 90% of the time, there is a gap where the throttle spring is supposed to rest on the idle screw. After 20 mile blast canyon carving the other day sitting at a light coming home, a distinct change in the idle and overall feel of the engine abruptly started. Throttle body bolts were found loose, causing air intake issues. I have checked all vacum lines and replaced the oxygen sensor on the exaust, also replaced the intake manafold gasket and the Idle air control IAC, I have run OB1 diagnostic and only code 12 present. Do you think I have a bad IAC ? Aug 18, 2006 · My old throttle body was worn and air was able to get around the blades even when they were completely closed. All of my vaccum hoses are connected. Other times it will turn over within a second or two even if the engine is warm. Engine Warm: Idle: 10-15psi (not worried here as this is normal for LT1's) Mar 13, 2021 · Help us help you. Car is a '94 Formula LT1/T56. It idles at around 1400-1500. I disconnected the w/p temp sensor, and both fans came on, after reconnect both turned off. If the valve fails or has any issues it can cause the idle speed to be thrown off. Right now it idles at about 900 RPM which seems a little high to me. 6 rrs,and lifters,cnc stock ported heads,Walbro 255,edelbrock ported air gap intake,58mm t/b,pacesetter Lts,Summit 2. It never acted up until it got good Mar 9, 2012 · With a scan tool hooked up & your Corvette running at idle, watch the IAC counts carefully on the data display. But the fact the idle speed varies may be related to other problems. 10s , flowmaster 80s , high flo cat , throtel body bypass , descreened and ported maf. Simultaneous readings of coolant temperature and idle RPM will address the idle speed issues you originally posted. I upgraded to the zl1 pump and ADM controller at the time I supercharged the car. Also air inlet temperature is installed. My idle is getting better, but then again it's been very cold here, and it seems to surge more in the warm weather? Apr 3, 2016 · However, this IS possible on the LT1, I did it purposely on my car and found the ECM will respond to a leak on ONLY one side with fuel trims. is there anther sensor to look at. 2L, automagic transmission cheesy and only 96. Feb 1, 2020 · C4 Tech/Performance - 1992 corvette high RPM at idle issue - HI everyone, i been having issues with high rpm at idle. Reving the engine off idle gradual up to 2,000RPM's, if the IAC is working correct, IAC counts will increase higher numerical. If you find a used computer from a similar car, lt1 camaro or firbird, with the same transmission. Mar 16, 2012 · I was reading an article on the LS1 site about throttle blade positioning and IAC relationship and realized my manual idle adjustment screw was turned way out holding the throttle blades a lot more open than it should have been at idle. as far as I know, the only engine in any '94 Z28 is an LT1! A forum community dedicated to 1st generation Chevy Camaros Mar 3, 2019 · My issue is with a stubborn low idle condition - when warm it will idle at 600 RPM regardless of load (in gear or in neutral, AC on or off, electrical load high or low). May 1, 2013 · I'm at a loss and hoping someone can help me find the correct solution. Question 1 All of a sudden, the idle is way too high. Idle is normal. Chevy dealer sponsored 67 retro SS nose stripe package. I have done the following: I investigated for an intake leak, and didn't find one -- I replaced the intake gaskets again for good measure and torqued everything down to spec. They assume the gasket is good if theres no water in oil or oil in water. For high performance applications we recommend the use of high output ignition coils. Problem is only at full throttle. YES it has a new EGR. when I put it in neutral the engine will run smooth but while in gear it will not run smooth. I have replaced all ignition and fuel system components, including: Optispark, Ignition Wires, Spark Plugs, ICM, Coil, Fuel Pump, Fuel Filter, and verified each and every fuel injector is operating properly. Still it is idling high. 2. I just had to replace the VAT module (ECM not re-programmed) and have had it back on the road a few days. The automobile fault code P0507 indicates a problem with the idle control system. The main difference between the LT1 and LS1 fuel delivery is that the LT1 attempts to maintain a constant relative pressure between the fuel rail and intake manifold pressure (pressure varies with manifold pressure), whereas the LS1 maintains a constant absolute fuel pressure (doesn't change). My car is an M6. After it stalls it starts right back up with no problem but still revs up and down at idle. KILLS=SRT4,GTI,LS1 Z28,08 BOSS GT MUSTANG,SUBURBAN CAMED,CIVIC HATCH,COBRA SVT , TRANS AM LT1, COBALT SS SUPERCHARGED. Thinking of replacing the tps and Jul 8, 2013 · From a few years of reading about leakdown in the forums "IMO" odds are In this order 1- fuel pump check valve (in the pump) , 2- regulator vacuum diaphragm leaking into the manifold (pull vac line and smell gas) , 3- Regulator leaking pressure back to tank (have to plug return line to test, not easy to accomplish) , 4 - Leaking injector (have to pull fuel rail w/injectors intact, hit key Oct 2, 2011 · 1995 Camaro LT1/T56 high idle! Jump to Latest 3K views 4 replies 3 participants last post by Mystery Bird Oct 4, 2011 Aug 15, 2003 · A bad IAC, especially on a MAF vehicle can cause all kinds of drivability issues. 08 V steady at idle, but sometimes stayed high (0. Looking for direction on where to start to diagnose what the hell went wrong. I Replaced Opti For Msd Distributor, Cap, And Coil Along With Icm, Wires And Plugs, Fuel Asked by Chiefmitch2003 · Sep 15, 2003 · Welcome to the wonderful world of LT1 idle skip tracing. I let my tuner know about these upgrades and gave him the fpcm data from ADM. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc. I had to feather the pedal to keep idle. Aug 21, 2012 · SOURCE: trying to wire a 1994 lt1 into 1996 chevy s-10 It should be a plug and play if your using the ECM for the 1994 engine. 40 over, 272 crane cam, heads ported,polished,plained. This wire runs from the optispark to the coil. Would this hesitation (or soft low end off idle) be normal? 3. When it's cold, it will stay in high for 1-3 minutes. 4. We checked the reference voltages and grounds at the appropriate wires of each connector. Apr 16, 2023 · Help us help you. If you even just moved the wire, it will likely change your symptoms intermittently at least. D C4 Tech/Performance - Help me with my LT1 high idle, out of ideas - Back story: I bought a 92 in July and have been slowly bringing it back to working order. If the idle speed is 600, there isn't enough power to get the car moving when you stomp on the gas. Mar 17, 2008 · The STOCK fan settings are high: 225* low speed, 235* high speed. May 15, 2022 · An intermittent issue with the coolant temp sensor could explain variations in idle speed, and explain the coolant fans suddenly turning on. 2014 Z51 Coupe, Cyber Gray Metallic, Gray interior w/suede seat inserts, exposed carbon fiber roof panel, 7-speed manual, 2LT, non-NPP, non-mag ride, non-nav. The most common symptoms are surging/hunting idle, or an idle that’s way out of spec (400rpm, or 1500rpm), stalling when coming to a stop, causing the ECM to have an erratic integrator value, accompanied with a moderately swinging A/F ratio. I'm a carburetor guy with no experience with computer-controlled engines. 98 @ 122 Jun 4, 2016 · It was a bad optical sensor in the Opti-Spark distributor. The idle was so rough that the car would sputter and die or level out around 300rpm. In severe cases, the engine may even stall. Worn out plugs and bad plug wires will cause rough idle but rarely cause stalling. this engine was apparently rebuilt and runs well, no Mar 13, 2009 · One day, I drive the car home and park it. Nov 29, 2012 · C4 Tech/Performance - '95 LT1 Corvette - High Idle - Odd week with this car. I was told it was due to not enough air at idle, not too low a idle setting. 5:1 forged 4340 crank, forged H beam rods, forged -5cc Mahle pistons, H series bearings all around, B&M flex plate, keyed hub, LE2 heads, custom LE grind, LE ported intake, BBK 58mm, LS7 lifters, comp hi-tech push rods, 1. Oct 20, 2012 · The varying pressures is normal with the LT1. By two torque screws. It's very faint, and only immediately off idle. The car idled low, almost dying when throttle lifted due to potential vacuum leaks. Jul 25, 2011 · The pcm controls the idle by changing the iac counts to adjust for different load factors, if the pcm is not doing its job, it could cause the idle surge you have. lt4 cam. Also, the idle speed adjustment screw seems to be frozen or maybe has lock-tite on it. Searched for vacuum leaks. IT has a rich 02 sensor signal saying around 700mV as you stated. At least in my truck, TPS is ALWAYS suspect. Idle seemed better so I went and took it for a short spin. Mar 16, 2011 · C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine What are the Symptoms of a Bad Idle Air Control Valve. Jun 28, 2012 · Usually RPM differences are smaller and the PCM uses timing retard or advance to quickly adjust idle (idle overspeed and underspeed timing tables), and then IAC more gradually to get it correct. May 10, 2011 · Alright, went and learned how. Jul 8, 2011 · I have a 94 Corvette LT1, auto transmission, with an engine idle surge problem. You have all the advantages of OBDII (like reprogramming them via software) without being governed by the OBDII smog laws. Jun 27, 2016 · Just installed a Racetronix 255 fuel pump and harness because my old pump was not keeping up at WOT, changed fuel filter as well. Since I've had it, the engine has bogged down a bit when first put into gear (somewhat intermittent, may be tied to engine temp). It does not do this constantly, but I would say almost the majority of the time. The idle surging will usually go from around 800 to 1500. Give Tim240 a heads up on this one. The problem I am having is my fuel pressure reads 51psi at prime, 50 to 51 at idle, and when I disconnect the vacuum to regulator the pressure goes up to 54psi, then when I shut the engine off, I loose all pressure in a few minutes. 6 nsa Pro mags, patriot golds, 42lb green tops, ARP bolts all around, canton 6qt pan, pacesetter coated long tubes backed by a magnaflow Aug 27, 2010 · I have a 1992 chevy caprice it has a 350 TBI in it. No issues with fluctuation or dropping regardless of vehicle acceleration. It got worse, much worse until it was replaced. Re-sealed intake manifold, replaced IAC, ICM, COIL, TPS. No codes present, and otherwise runs like a dream. Jun 19, 2005 · C4 Tech/Performance - LT1 Ignition Control Module effects timing advance (!) - The timing advance is controlled by the PCM via timing tables which specify X degrees of advance for rpm vs. Cleaned the throttle body bolted the new sensor and also bypassed the coolant lines while i had Jan 21, 2018 · Symptoms: intermittent high idle intermittent surging at idle Warmed up, slowing down for a stoplight or something, it does not want to idle down. It also ran pig rich. 73's and stall Feb 18, 2000 · 1994 Camaro Z-28 High Idle Problem. The most common cause of this issue is a dirty throttle body, which can disrupt the airflow and affect the idle control. Now my engine is upgraded and the idle is a little low. My '95 has a slight skip that moves around at idle, but oddly mainly when idling in neutral or park-- in gear (auto trans) with the brake on the skip seems to go away. Its just like when I see people posting about blown head gaskets. The Corrlc corrections need to be changed as the transport delay from the exhaust port to the o2 sensor has gotten longer at lower engine speeds and slightly higher as engine rpm climbs. The lower hose on the water pump is the heater core inlet, and should have a flow restrictor mounted in the hose. Related: Faulty PCV Valve Symptoms Aug 11, 2019 · The 95 LT1 Z28 automatic convertible experienced high idle after a head gasket job. Could this be air idle valve again. Not high RPM issues. When moisture and dirt get inside the actual distributor assembly, it creates various symptoms such as stalling, erratic idle, and miscellaneous engine malfunction codes (GM OBD1 as well as OBD2). 7 LT1 {engine swap in the 90s} A/T. also i tore the intake off today to change the gasket and came to realize ther was a sensor unplugged on the drivers side in the back of the intake. I've done a lot of looking online and am not liking what I'm seeing. Dec 22, 2010 · Check your coil wire. Then they drop like a rock. I will try this and I will let you know. Then when it hits a specific time frame idle climbs to approx 3000rpms and hangs there. 5. This occurs in "park" and ""neutral" as well as Dec 16, 2010 · It's even easier to just have the one switch, then have a diode between the cold advance and high idle (allowing current in that direction). I would think an OBDII code reader should work. Oct 20, 2007 · mines set to 775 in gear, 800 in park. IIRC from my 94 TBI, 10° BTDC, idle 850-900 @ 1000 rpm. New distributor,wires,o2 sensors, mass airflow and map. . May 19, 2014 · Here's a breakdown of the symptoms. MAP sensor at idle was about 1. The use of aftermarket high voltage products will shorten the life of the distributor cap and rotor. Gary Doug or cocobolo out help me out fella,s. 8vdc, didn't try WOT as it was early Sunday morning. Once at a stop, it is around 1,000 RPM then eventually settles down. Dec 10, 2024 · Vibration at high rpm, shaking at idle Jump to Latest 42 views 6 replies 3 participants last post by rls355 37m ago Nov 12, 2010 · C4 Tech/Performance - 94 LT1 erratic idle - what can cause this. New fuel pump in it and it wont hold a idle. If the idle speed is lower than programmed, it will increase the counts. . This may result in an unusually high or low idle speed, or in some cases a surging idle speed that repeatedly climbs and falls. Do these cars have a built in rev limiter? Feb 19, 2009 · 1995 z28 , abs 16" trans am rims , m6 , slp springs , k&n homemade cai ,3 inch exhaust,4. Several others with very similar symptoms have lead to replacing the Opti. Watching this video will help you diagnose to see if it is time to replace your idl May 29, 2015 · so i was driving through town and the car got really warm, warm enough to cycle the cooling fan on and off several times. 5mm plug wires, Summit polished diff cover, March crank pulley, V8 shock tower brace, core shifter/billet hurst, Sway bars, Hotchkis lower control arms, welded subframe connectors, lakewood drive shaft loop, non cracked dash Feb 19, 2020 · I'm helping my father with his 96 LT1. The easier it breathes, the more power it will make. Nov 17, 2014 · my 95 /Lt1 idles at 900. Local shop said distributor cap needed replacing. Sep 18, 2011 · Ok so i figured it out. Put it in drive and it lunged and kept a high idle. Somewhere around 25 to 55 counts for the IAC with the engine fully warmed & at idle is normal. Feb 16, 2010 · Mueller: LT1 Reverse Flow Cooling System "Coolant to the heater core comes from the water pump. 545 Volts. Got in it this morning and ran well. Mar 21, 2018 · Symptoms of a failing idle air control valve. Went to work on the freeway running fine. C7 Carbon GTX carbon fiber rear spoiler, Z06-style carbon fiber splitter and skirts. Idle BTW is perfectly smooth. Jun 23, 2010 · I had a high idle at park and my car would stumble and stall when stopped in drive at a stop light. I changed the plugs, the wires, exhaust manifold gaskets, fuel pressure regulator, mass air flow sensor, 02 sensor, idle air control valve, etc. And while these symptoms are common for blown head gaskets, not all blown head gaskets produce these symptoms. Sep 11, 2013 · 1995 Chevy Caprice 9C1 LT1 Former Saratoga Sheriffs Car * Performance Mods- Gen 2 Tri Y Headers, Hi Flow Cats, Spin tech catback w x pipe, RAISS Intake, Rustic #750 Front Springs, Bilstien Shocks, UMI Rear Upper and Lower Control Arms, Dick Miller Racing Bars, Speed Tech Front Upper Control Arms, Factory 9c1 Front Sway Bar, HA Rear Sway Bar Jan 8, 2002 · My symptoms: slight stumble or dropped cylinder at idle, it was very intermittent, a sudden jump on the tach. Get in after work and it did not want to start and when it did it ran rough. I replaced the IAC valve and it still idles high. (this forum does not allow attachments). Throttle response and blips of the throttle is NO problem for the first 15-30 seconds. Occasionally the problem simply disappears Oct 28, 2009 · Most of those systems would cause the symptom at idle, at all temps. Check on PCV valve, replace/install if necessary.