1982 High Idle
Thread Starter
Heel & Toe
Joined: Sep 2024
Posts: 16
Likes: 2
From: Lake Orion, MI
1982 High Idle
Hello guys, I looked for info on this topic and could not find. If I missed it, please point me in correct position. Anyway, I have a 1982 that has a high Idle. When starting cold, it idles around 1400 and then will kick down to 1000ish when warm. In gear it will be roughly 900. I have adjusted the fuel pressure 11.5 psi, balanced the throttle bodies to 6 in of h2o. So it is running really good, just idling high. I also did this. With engine warm and off, I disconnected Rear IAC harness only. Started engine, idle went to 1500, Turned off. Left Rear IAC unplugged and then unplugged front IAC. Idle went to 2000. I turned off, plugged both back in and idle was 750. Thought I had fixed it, by somehow resetting the ECM. Went out today and I am back to 1000ish and 900ish in gear. Idle is smooth and performance is good. I hear that ECM controls idle, so not sure what to do from here. Appreciation in advance.
Race Director
Joined: May 2006
Posts: 18,758
Likes: 2,590
Hello guys, I looked for info on this topic and could not find. If I missed it, please point me in correct position. Anyway, I have a 1982 that has a high Idle. When starting cold, it idles around 1400 and then will kick down to 1000ish when warm. In gear it will be roughly 900. I have adjusted the fuel pressure 11.5 psi, balanced the throttle bodies to 6 in of h2o. So it is running really good, just idling high. I also did this. With engine warm and off, I disconnected Rear IAC harness only. Started engine, idle went to 1500, Turned off. Left Rear IAC unplugged and then unplugged front IAC. Idle went to 2000. I turned off, plugged both back in and idle was 750. Thought I had fixed it, by somehow resetting the ECM. Went out today and I am back to 1000ish and 900ish in gear. Idle is smooth and performance is good. I hear that ECM controls idle, so not sure what to do from here. Appreciation in advance.
Thread Starter
Heel & Toe
Joined: Sep 2024
Posts: 16
Likes: 2
From: Lake Orion, MI
I don't have a scanner. Some more info. I took a reading of my TPS at idle. I can not get it lower that 1.2 volts. I have read that it should be .54 V. It does move slowly when I open up throttle plate...... I have also read in another thread to adjust initial idle on rear TB, but I do not see a screw. I only see the screw that adjusts vacuum.
Instructor
Joined: Aug 2023
Posts: 208
Likes: 44
From: San Antonio, TX
You've got the balancing procedure half-way there (based on what you wrote). Your RPMs could be high due to not setting the TPS after balancing the throttle bodies.
Also, the recommendation for fuel PSI is 13. I have mine set to around 13-15PSI.
While you have got the 6inches (presumably on both sides), that is to set the baseline for air intake. Having it at 6inches will no doubt have you run a high RPM.
The correct procedure for balancing the throttle bodies is as follows:
Also, the recommendation for fuel PSI is 13. I have mine set to around 13-15PSI.
While you have got the 6inches (presumably on both sides), that is to set the baseline for air intake. Having it at 6inches will no doubt have you run a high RPM.
The correct procedure for balancing the throttle bodies is as follows:
- Warm up to operating temp then turn off.
- Disconnect IAC's on both TBs, plug air holes in the throttle bodies
- Re-start the engine and put into drive (be sure to chock and set the parking brake)
- Using the manometer, verify both throttle bodies are showing 6 inches, if not, adjust throttle stops until 6 inches is achieved.
- Make sure to use the middle port on both throttlebodies
- be sure to plug the vacuum port for the air cleaner thermac
- Once balanced, the rear throttle body (driver side) needs to be adjusted down until the RPMs are at 475 RPM
- I would not trust the tachometer on the car, mine shows around 150-200 off. Instead, I got an Innova tach/timing light
- Attempted to use WinALDL as well but can't help but feel as though it sets the ECM to a mode that throws off the balancing procedure.
- 475 is the shop manual rpm. I have mine set to about 550 but looking to bump it up to 650 or so.
- Put car into neutral, turn off engine
- Use a multi-meter and set the Throttle Position Sensor to +/- 0.525v
- If you don't have a connector between the throttle bodies, you can make one for fairly cheap or buy one (Xfire Performance) has them for about $32 + shipping.
- Make sure that you check the bottom two pins of the TPS sensor. Anything else will give you an incorrect reading.
- Remove plugs from TB's, reconnect IAC's
- Restart engine, let run for a few minutes. The RPM's will idle high for a minute or two and then come down.
- Take for a drive and get to 35 MPH for a little bit
- Alternatively, connect a drill to the speedometer cable and get up to 35 MPH
Last edited by klturi421; Jun 10, 2026 at 08:19 PM.
Thread Starter
Heel & Toe
Joined: Sep 2024
Posts: 16
Likes: 2
From: Lake Orion, MI
Thank you klturi421 ! I read the same thing in the Shop Manual. I guess I am scratching my head as to why you adjust the rear throttle body to 6in H20 and then the Front to 6in H20, and then turn the rear down to lower idle. Won't that throw off the balance? I guess intuitively it does not make sense.....Since I have mine balanced at this point (although it was in park), could I not just turn the rear TB screw until I get desired RPM? If it is best, I will do the full procedure....as I am so close and have come so far....why not ??? I love the challenge ! Please advise and thank you.
MK
MK
Instructor
Joined: Aug 2023
Posts: 208
Likes: 44
From: San Antonio, TX
Thank you klturi421 ! I read the same thing in the Shop Manual. I guess I am scratching my head as to why you adjust the rear throttle body to 6in H20 and then the Front to 6in H20, and then turn the rear down to lower idle. Won't that throw off the balance? I guess intuitively it does not make sense.....Since I have mine balanced at this point (although it was in park), could I not just turn the rear TB screw until I get desired RPM? If it is best, I will do the full procedure....as I am so close and have come so far....why not ??? I love the challenge ! Please advise and thank you.
MK
MK
I would make sure you're in drive when setting the base RPM. I had it in park when I set it and it throws everything off.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
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
Melting Slicks
Joined: May 2021
Posts: 2,281
Likes: 1,325
From: Fleming Island, FL
I don't have a scanner. Some more info. I took a reading of my TPS at idle. I can not get it lower that 1.2 volts. I have read that it should be .54 V. It does move slowly when I open up throttle plate...... I have also read in another thread to adjust initial idle on rear TB, but I do not see a screw. I only see the screw that adjusts vacuum.
Last edited by Fly skids up!; Jun 11, 2026 at 07:22 AM.
Thread Starter
Heel & Toe
Joined: Sep 2024
Posts: 16
Likes: 2
From: Lake Orion, MI
Thanks Fly Skip up. I am going to rebalance the TB to 6" as suggested and then turn the Rear one down to get lower idle and then check the TPS voltage. I will keep you guys posted. I appreciate your help.