When im at idle my car runs smooth until i turn the heator the front defroster on then it runs rough It runs smooth agian once i turn it off.what could be the problem.Thanks

 

Does it run roughly when you have the AC on too?

If it's running roughly when the AC/Defroster is on, it might have something to do with the compressor. It puts extra drain on the engine. Usually not enough to make it run badly, but you will notice a difference. If it's running bad whenever the temperature controls are set to anything other than off, I have no idea.


------------------
89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

My car kind of vibrates when the heater is on, I think its just that--not a rough idle.

Enkil, your iroc has TBI?