What's up with my idle?

[georgio440]

It'll hover around 600RPM for a bit, then jump to around 900RPM for a little while, and then it'll go back down to 600RPM. Is this normal?

 

[blkhorse]

a/c compressor turning on? a/c also comes on when you have your heat selected to defrost

 

[georgio440]

Nope, nothing on.

 

[Spro]

Your fan may be turning on without you even realizing it. That will make the idle come down a little bit. If not the fan, clean the IAC and see what happens.

 

[281CI96Coupe]

It's normal lol. When stangs get old, they get the "surging idle". Everyone on this board love saying the IAC, and I believe it is.

 

[joshheat25]

I have that surging idle and it's done that for ahh 2 years. Only when the engine is at running temp and when it's in park. I tried everything I gave up on finding out what it is..

 

[eliteJAE]

Your fan may be turning on without you even realizing it. That will make the idle come down a little bit. If not the fan, clean the IAC and see what happens.

+1 it surges when the fan comes on when in idle, which is normal, and itll also surge a bit when you pump the brakes at idle, also normal.