I've noticed recently that with the A/C on my Z28 idles and runs crappy. I don't use A/C much because of the t-tops, but the few times that I have the kids or wife in the car, I have it on.

I know the A/C is a load on the engine, but does it affect that much that idling is rough? It doesn't actually die, but the "in gear" idle drops to around 700 rpm..usually it's around 800 w/o the A/C on. Also, driving is kinda sluggish and not as responsive. Is it the A/C or just the hot outside air? Would a tune help this issue? I have new plugs...would new wires help?

 

I haven't noticed any significant change in idle or performance with the A/C running in my car and I run the A/C a lot (a black car with a dark & grey interior hots up something fierce)

It's been over a month since I have been able to drive my car and will probably another week and a half, give or take before I can again to check this out.

Maybe there's a bigger problem with your A/C or general tune?

Did this help? Probably not . . .

 

when i got my cutout... i noticed it was a bit louder when a/c was on lol.... i always messed around with friends, this is loud mode, lol


-cory-

 

Hell, my in gear idle is only 550 rpms. But the car idles pretty good.

 

no difference that anyone could tell.. I think you need to check your car out..

 

The PCM knows when the A/C is on and the IAC motor should keep the idle at specification. If your A4 is normally idling at 800rpm, you may have a problem. The stock PCM settings for the A4 are 550rpm in gear and 650rpm in neutral. If you throw in the normal stock tach error of 100-200rpm, you might be OK on the idle though. You need to read the idle speed directly from the PCM with a scanner to get an accurate number.

Might be the IAC passages are plugging up or the IAC motor is dirty and the IAC counts are max'd out at normal idle, and the PCM can't open the motor up any more to compensate for the added load of the A/C.

Needs a good scan to observe the actual RPM and how the IAC counts respond to the A/C turning on.

 

My car as well as every vehicle I've ever driven gets a little 'sluggish' when the A/C is on - it's increased drag, simple as that. I guess some people just aren't as sensitive.

But, the car should idle fine with it on. Check your IAC first like Injuneer said... common problem that causes several different symptoms including low idle.

Also, isn't there some kind of switch that works with the PCM to tell it the A/C is on? Maybe it's shot and not sending the signal? I may be wrong.

 

Hey mako & Injuneer;

Gracias for the figures you guys stated. My '02 Z A4 has been idling, in gear, at about 550 rpm. Thought something was wrong. Amazed what I can learn on these threads, all thanks to you fine people.

Steve

 

Okay..will check the IAC/IAM first...thanks for everyone's reply. I'll have it scanned to be sure...those tick marks on the tachometers are so close, I think the needle is as wide as the gap b/w the tick marks.

 

The numbers I quoted were for the LT1 stock programming. I don't know anything about the stock programming for the LS1's.

 

I'll check it out, Injuneer.

Steve