High Idle that won't come down.
Thread Starter
Joined: Apr 2005
Posts: 518
Likes: 0
From: South Dakota
High Idle that won't come down. I have a 96 Firebird Formula 6-speed, that I am trying to get back on the road. The car has a Lunati 237/242@.050 .525/.525 110 LSA cam and headers. The intake, throttle body, and MAF are stock. The tune that was in the car when I got it was not very good, so I sent the PCM off to Soloman. After getting it back the car will not idle lower than 1300 rpm cold or hot. I have checked for vacuum leaks with carb cleaner, and found none. I checked the TPS voltages and it is at .578 volts at idle and 4.58 volts at WOT. I suspect the IAC, is bad. I pulled the connector off the IAC, and found corrosion on the contacts. I cleaned the contacts, and it still high idles. The code scanner I have does not have IAC counts in the live data. Is there a way to test the IAC without a scan tool? Is there something else that will cause it to high idle?
Last edited by seawolf18; Apr 26, 2019 at 09:30 PM.
Teching In
Joined: Dec 2011
Posts: 41
Likes: 0
From: New York
You need to see where the IAC counts are. And where the desired idle rpm is set. My guess is the throttle blades are opened to much causing you to idle high and have 0 iac counts (which is all the way closed) and not being able to reach the desired rpm. Or the IAC is faulty.
Thread Starter
Joined: Apr 2005
Posts: 518
Likes: 0
From: South Dakota
The idle is supposed to be 800 RPM warm. Did some more messing with it. I unplugged the MAF and started it, and its still at 1300 RPM. I then removed the intake tube and started it. I then partially blocked off the IAC hole between the butterfly's, with my hand, and got the idle to come down to 800 like its supposed to be. I'm thinking the IAC is stuck and it needs replaced. I also had a P0154 code oxygen sensor bank 2 sensor 1 not responding. I unplugged the passenger side o2 sensor, and pulled up the wiring to see if its burned off. The Harness side of the wiring looked and tested out ok. I tested the sensor itself with a meter, got OL on the two gray wire pins and continuity on the two white wire pins. Looks like I need to order 02 sensors as well.
