I am posting this for a friend. He has a 94 Civic Ex. The problem is that everytime he starts up his car when it is cold, the rpms will jump up and down from about 1k to 3k for a minute or two. I cannot figure out what the problem would be? Anyone know what the problem might be?

 

does it surege or does it just say at 3000 for a little while or does it go 1000-3000-1000-3000....etc.?

if it just stays up then its normal its just trying to bring the engine up to normal operating temp.

if it surges then it may be his coolant temp sensor or it might be his IAC.

 

It surges 1000-3000-1000-3000. What does IAC stand for?

 

I had the same problem with a bad throttle body gasket. All it is, is a leak somewhere on the intake end of things.

 

could be a vacuum line too...

 

With this problem would it only surge up and down at start up?

 

if its a gasket leak, yes. once the car warms up and the metal expands a little, the leak could be closing up, letting the car idle correctly.

 

if its a leak it wont surge it will just rise really high. its your Idle Air Control Valve. wheres his idle when its in drive? if its high then it may be a leak but if its normal its most likely his IAC valve.

 

Yea his idle is normal after it does the weird idle for a minute. So I'll have to tell him to check into that IAC Control Valve. How much do those cost for a new one? Or whatever would need replaced?

 

check the Fast idle also,..my friend at the same problem and i tighten up the Fast idle and it idled fine after that,..if its the IACV,..take it off and clean the screen