idle issue
Thread Starter
Pro
Joined: Oct 2011
Posts: 716
Likes: 0
idle issue
okay, I have a 94 LT1 with 6 spd manual tranny. My idle is 825 ,and the computer says it should be 750. I have tried to do a smoke test, that showed no vaccu leaks, sprayed everything with cleaner, which also failed to change anything. I replaced the idle control valve.
Now, don't get me wrong, it runs perfectly fine.
any other ideas? also they tried to reset the base idle and it did not help
Now, don't get me wrong, it runs perfectly fine.
any other ideas? also they tried to reset the base idle and it did not help
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
How are you checking RPM? Via the built-in tach?
Disco the throttle cable from the TB and check again.
Forum search on R&R and cleaning IAC.
RPO C68 Electronic Control Air Conditioning? If so, if you hold down the up and down arrows for the fan speed for 10 seconds, the fan speed display will show '00' then press up fan speed until it shows 6. The number displayed * 25 will be the RPM the computer sees. (IE 750 RPM would show 30, 825 RPM would show 33)
Disco the throttle cable from the TB and check again.
Forum search on R&R and cleaning IAC.
RPO C68 Electronic Control Air Conditioning? If so, if you hold down the up and down arrows for the fan speed for 10 seconds, the fan speed display will show '00' then press up fan speed until it shows 6. The number displayed * 25 will be the RPM the computer sees. (IE 750 RPM would show 30, 825 RPM would show 33)
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
There is a tolerance on the idle built in to the ECM programming. On my '86 it's +/- 75 RPM, so it gets within 75 RPM and says that's "close enough". I don't know if that tolerance changed in later years.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Specs for all GM's without electronic throttles: Park/Neutral - Actual Idle 100 +/- rpms from Targeted; Drive - Actual Idle 50 +/- rpms from Targeted. Assuming it's in Neutral, it's within specs. If you want something different, you'll have to reprogram. Quick IAC test: Note idle rpm. Turn it off. Restart. New rpm should be higher than noted rpm, but return to that noted figure within a couple of seconds.
