98 Sport....IAC ?

[RichRed98]

Hello all. Other than the loud whine from a bad IAC, are there any functional symptoms to confirm this as a problem? During the first few miles of warming up, my 98 Sport Rpm's go up to about 1100 and down to 300 back and forth stopped. Seems to go away when up to temp. Any suggestions? Besides the IAC, could it be fuel filter or pump going bad?


Stock 98 Explorer Sport
118,000 miles with all original components under the hood

 

[scucci]

Typical symptom of leaky manifold gaskets.

 

[XLT]

If it has issues idling when it gets cold out it could point to the IAC. Quick fix to rule out the IAC is to try and clean it and go from there.

 

[chapsdeva]

My bet is intake gaskets.

 

[Carguy3J]

Most likely a bad IAC. Don't even bother trying to clean it. You'll never get it all. While the idle is "surging", unplug the IAC. If the idle smooths out, there's your problem. If not, then keep looking, as it could be the intake leak others have mentioned.

 

[RichRed98]

Thanks for your help....I'll start with the IAC.