98 Cherokee 4.0

Trouble Code P0505

I have a bad IAC with no fast idle. You need to give it some pedal to start, Vehicle runs but low idle is a wee bit slow.

I picked up a new IAC from Rock Auto, it's a "Standard Brand" part.

Codes were cleared.

RPM races to 3,000 rpm and won't idle down. I tried driving it to get it to sync with the computer.

Thinking it's a bad IAC from Rock Auto, I picked up a $11 China IAC from Amazon as a check. This China IAC does the same thing.

Put the bad IAC back on it runs but has no fast idle during warm up.

Suggestions?

 

Go with OEM (p/n 4874373AB), looks like it's about 100 bucks at an OEM online Mopar parts dealer, can probably find it cheaper. Besides that check for vacuum leaks, make sure the new ones have the o-ring installed, I'd be surprised if an 11 dollar IAC came with an o-ring at all but I dunno.

 

Don't cheap-out with the IAC. Also, take the manifold it bolts to off to clean the seat where the conical portion of the IAC seats. There may be a slight build up of contamination preventing it from fully seating, resulting in a poor idle. Or, taking the throttle body off completely is just as easy and then you can spray it down with cleaner (IAC off). My 98 was not idling properly with a new IAC because of contamination in the manifold it bolts to.

 

this as well I had to take he extra step of putting mine in Berryman's Carb Dip for 4 hours after a whole can of throttle body cleaner and a ruined stuff bristled brush still hadn't got the job done to my satisfaction. The iac manifold was awfully caked up

 

Thanks for the suggestions, all place have been cleaned, hoses are ok. First IAC I put in was a Standard Motor Parts IAC, they make decent parts. After that gave me a 3000 rpm idle I did buy a cheapy china IAC for a double check. Note withoriginal IAC back in I have normal idle and no fast idle.

 

And you have orings on the replacements?

 

(fast idle went obsolete with carburetors)
Is the o-ring from the original IAC stuck in the bore?

 

Of course.