1996 CE LT1 auto engine idle
Thread Starter
Instructor
Joined: Nov 2006
Posts: 100
Likes: 0
1996 CE LT1 auto engine idle
After installing a Hotcam and R/R's I had the PCM recalibrated by PCMforless who appear highly recommended by other members.
The engine now constantly idles at 950rpm which seems very high, the throttle body is clean and I have recently changed the IAC valve and TPS which has made no difference to the idle.
I read somewhere the idle is controlled by the PCM,
so has the PCM been modified to idle at 950rpm due to the mods I have installed or should I be considering other issues, I am sure the stock idle was in the region of 650-700rpm, apart from my concerns on the idle the engine performs well.
Thanks in advance
The engine now constantly idles at 950rpm which seems very high, the throttle body is clean and I have recently changed the IAC valve and TPS which has made no difference to the idle.
I read somewhere the idle is controlled by the PCM,
so has the PCM been modified to idle at 950rpm due to the mods I have installed or should I be considering other issues, I am sure the stock idle was in the region of 650-700rpm, apart from my concerns on the idle the engine performs well.
Thanks in advance
Le Mans Master
Joined: Oct 2004
Posts: 7,706
Likes: 485
From: Everett WA
C4 of Year Finalist (appearance mods) 2019
In all seriousness, this would be a great question for PCMforless. IF for example you told them that this car is a daily driver and you do not want any drivability issues, they may well have set the idle speed up higher.
I had this done on mt 95A4 when I went with the hotcam & LT headers because I drive in stop & go traffic every morning. My idle is set to between 900 - 950
I had this done on mt 95A4 when I went with the hotcam & LT headers because I drive in stop & go traffic every morning. My idle is set to between 900 - 950
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
One quick thought...
after replacing the IAC did you retrain the PCM?
Not sure on your year, but for the 94 LT1, you slightly depress the gas pedal, then start the engine, take foot off gas pedal, let idle for 5 seconds, turn off, for 10 seconds, then restart -- it recalibrates the IAC -- just did a cleaning on our 94's TB and IAC chamber (removed IAC), afterwards recalibrated IAC and idle dropped, so it did work.
after replacing the IAC did you retrain the PCM?
Not sure on your year, but for the 94 LT1, you slightly depress the gas pedal, then start the engine, take foot off gas pedal, let idle for 5 seconds, turn off, for 10 seconds, then restart -- it recalibrates the IAC -- just did a cleaning on our 94's TB and IAC chamber (removed IAC), afterwards recalibrated IAC and idle dropped, so it did work.
Thread Starter
Instructor
Joined: Nov 2006
Posts: 100
Likes: 0
1996 CE LT1 auto engine idle
Thanks for the replies, yes I recalibrated the TPS as per instructions found on this site, but unfortuantely made no difference, would you think an idle of 900/950rpm was high considering these mods,
Thanks in advance
Thanks in advance
Thread Starter
Instructor
Joined: Nov 2006
Posts: 100
Likes: 0
1996 CE LT1 auto engine idle
Sorry have no video, the work was difficult enough without attempting to video it, but take a look at this website http://shbox.com, this guy is fantastic at what he does, endless amounts of information on the LT1 with pictures that I followed and managed to complete the work without any big issues.
The hotcam has a slight lope to the idle and there is a big improvement in the power, I also installed an MSD optispark, meziere electric water pump (big difference on the running temp) and the LT4 knock module which appears has also made an improvement to the performance.
The hotcam has a slight lope to the idle and there is a big improvement in the power, I also installed an MSD optispark, meziere electric water pump (big difference on the running temp) and the LT4 knock module which appears has also made an improvement to the performance.
Racer
Joined: Feb 2004
Posts: 251
Likes: 0
From: De Pere WI
I just had engine rebiult with same mods and have pcmforless chip also. Engine rpm about the same. Ran my first time last weekend. There is a procedure to learn idle in manual but you need a tech 1 computer per book. Next week I plan to put on tech 2 and use the idle learn procedure per service manual and see what happens to my idle. When filling out request with pcmforless did you check the box to set idle at tuners preferance?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
with the above and as stated by Mr Peabody as well.Normal to increase the idle a bit to smooth things out. Call or e-mail and I'm sure they'll tell you. You're just wasting time and money until you follow thru with step 1.
Thread Starter
Instructor
Joined: Nov 2006
Posts: 100
Likes: 0
Thanks Guys, appreciate your response, PCMforless made the decision on the idle, they should know what the engine would need with those mods,
I am now convinced there are no issues with the idle and will continue to enjoy the car, only problem is the gas price in the UK, current conversion $125 to fill the tank.
I am now convinced there are no issues with the idle and will continue to enjoy the car, only problem is the gas price in the UK, current conversion $125 to fill the tank.
Burning Brakes
Joined: Apr 2006
Posts: 765
Likes: 0
From: Houston Texas
My '94: I have done these same mods and a few more, a pcmforless tune and sometimes my idle is 900'ish and fine in gear. Drop in the A/C and it goes down to about 600-650 and too low but you really feel the lope ... and sounds great. The sometimes 900'ish idle drops to 600 in gear w/o the A/C engaged and is too too low, so I think I am having a IAC problem or possibly injectors since it didn't idle smooth before the mods either but was about right (600-650) for the stock cam. I may be having a problem with the A/C ON sensor also, it should raise the idle at ON.
Before and after the mods I had the Hypertech tune on it and it ran great, but wouldn't idle worth a crap, sans the A/C.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
PCMFORLESS did the reprogramming on my 96 PCM running a 388 CID and 230/236 CompCams XFI cam. Idle was the same as yours and was what the engine called for.
Bryan can tell you what he set it at. I trust his judgement and experience.
Jake
Bryan can tell you what he set it at. I trust his judgement and experience.
Jake
