idle fluctuation at startup when a/c turned on

[jcjcf1]

This condition just suddenly appeared. When the car is started, idle is normal unless the a/c is turned on. With the a/c on, idle speed fluctuates (yo-yo) and gets so low that the engine stalls. Turn the a/c off, or wait until the engine is at least partially warmed up, and idle is normal with or without the a/c on.

I've done a search but didn't find anything specific related to idle fluctuation with the a/c on at startup. My car is a 92 CTSC(whipple) hi-boost with stock ecu/fic.

Suggestions? (Waiting to turn on the a/c until after the engine is warmed up doesn't count:biggrin Thanks.

 

[prestonmay]

i have same issue. have not investigated of even know if it is an issue---I just let the car warm up for a minute and then all is well(sorry):biggrin:. Assume the ac is pulling more power(gas and current) . I think my auto does the same, but its less noticeable---NO take off issue with no clutch....Maybe someone with give us the technical explanation. I have autorotor ctsc low boost....

Like you said you let it warm up for 30 secs or more its fine......Sorry, but I am glad to see I am not the only one.....Maybe we both are turning our AC on to soon..............:frown:

 

[Briank]

i have same issue. have not investigated of even know if it is an issue---I just let the car warm up for a minute and then all is well(sorry):biggrin:. Assume the ac is pulling more power(gas and current) . I think my auto does the same, but its less noticeable---NO take off issue with no clutch....Maybe someone with give us the technical explanation. I have autorotor ctsc low boost....

Like you said you let it warm up for 30 secs or more its fine......Sorry, but I am glad to see I am not the only one.....Maybe we both are turning our AC on to soon..............:frown:

My guess is you may have a bad fast idle valve or you need a throttle body cleaning.

 

[prestonmay]

I will clean throttle body Saturday. I am going to a Comptech Air Box


So I will do it then...

 

[camber_combover]

also check the vacuum hoses near the throttle body and around the intake area. Not sure of which ones are which but I recall one popped off mine in the area nearest the trunk/airbox side and that hose caused the idle to cycle up and down until i put it back on.

 

[davidf]

Hopefully it's not your idle control motor. Those are pricey though they rarely go bad.

 

[prestonmay]

great you guys gave me a couple of things to look at.

In all honesty. The rpm may drop from 1500 to 1200 in my case, so it was never a big concern for me to post until I saw the OP ask. The car was easy to take off with when I had the CENTERFORCE clutch regardless of rpm. Now that I have the Comptech PG 2 CLutch......One has to think for a split second due to the pressure pedal that baby has. I drive the car once a week avg, so as soon as I get use to the pedal pressure, 1 week or 2 go by and its back learning that clutch again (3 weeks installed to date) ....

I understand what all you are saying, but why would warming it for 20 to 30 secs change the behavior and outcome....

I assume the NSX has an auto choke? Unlike the rx7's I have owned, you could tell that they were on auto choke at startup (3k rpms) ....


Thanks again...I will look at all the above mentioned scenarios and post my findings.....

P.S. the Car never cuts off, but it makes it harder to take off at first crank up if the AC is turned on right away...
With this SC, feels like my car can go 10mph+ without giving it any gas coming off the clutch slow...never tested though....Too anxious to put my foot on the throttle...