High idle when AC/heater is running
Thread Starter
Teching In
Joined: Jul 2014
Posts: 9
Likes: 1
From: Lakewood, Washington
High idle when AC/heater is running I have an 89 GTA. It had a built up LS1 motor from a 2002 camaro SS.
My issue: when I turn the AC/heater in. The RPM's spike up to 2500 RPM's. After a while and only if I let the car sit. The RPM's will drop to normal op range. If I am driving and turn ac/heater on enroute. Samething RPM's go up and stay at 2500 RPM's. Which is sort of nice when on the freeway. I have an M6 so it acts like a Cruze control.
Anyways I have already replace TPS. So I am assuming this continuing issue is somewhere else. Has anyone experience this issue before? Were you able to resolve a fix?
My issue: when I turn the AC/heater in. The RPM's spike up to 2500 RPM's. After a while and only if I let the car sit. The RPM's will drop to normal op range. If I am driving and turn ac/heater on enroute. Samething RPM's go up and stay at 2500 RPM's. Which is sort of nice when on the freeway. I have an M6 so it acts like a Cruze control.
Anyways I have already replace TPS. So I am assuming this continuing issue is somewhere else. Has anyone experience this issue before? Were you able to resolve a fix?
I expect you have a vacuum leak somewhere, which is
not enough that the IAC bottoms out trying to hold idle
RPM (or maybe it's still bumped up, but you just don't
gripe about a 900RPM idle, don't say). But when you
turn on the A/C, an idle airflow adder comes in for the
drag torque, and now you've got even more air than you
need.
I'd look for air leaks in things like the PCV boot, gaskets,
brake booster, etc.
not enough that the IAC bottoms out trying to hold idle
RPM (or maybe it's still bumped up, but you just don't
gripe about a 900RPM idle, don't say). But when you
turn on the A/C, an idle airflow adder comes in for the
drag torque, and now you've got even more air than you
need.
I'd look for air leaks in things like the PCV boot, gaskets,
brake booster, etc.
Teching In
Joined: Apr 2025
Posts: 2
Likes: 0
From: Georgia
This is frustrating. I am currently having the EXACT problem.
I have replaced everything including the entire A/C system. New TPS, IAC and the tuner has been over a dozen times trying to tune it out.
was there ever a solution to this problem because I am stumped.
I have replaced everything including the entire A/C system. New TPS, IAC and the tuner has been over a dozen times trying to tune it out.
was there ever a solution to this problem because I am stumped.
TECH Senior Member
Joined: Jun 2016
Posts: 22,293
Likes: 3,617
From: Central Cal.
Good luck......
Moderator
Joined: Aug 2010
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From: Ann Arbor, MI
