Idle air (RPM)

[Pat]

A week or so ago my idle speed jumped from it's nominal setting of 700 RPM (set by my tuner years ago) to 1K.

I cleaned the throttle body and IAC device, checked that the throttle blades are closed and the action is smooth. the IAC plunger is not stuck but I can't tell if the solenoid is working. However the solenoid does have electrical resistance and there is voltage at the plug.

I searched for air leaks but couldn't find any.

As I understand it the idle air is picked up by a port at the front top (interior) of the TB, between the blades. Is that correct?

Could I still have a vacumn leak? What else can I do?

Thanks,

Pat

[CBT]

Try the ol' "unplug the battery for a while" trick and see if it resets itsself?

[Rockettman]

Do the rpm's go up / stay the same / go down (from your new level) when the the a/c compressor comes on?

[Pat]

The RPMs stay the same regardless if the car is in drive or park or if the accessories, radio, A/C or on. It's a constant 1K.

Additional observation, before the RPM's would return to idle very quickly, now it seems to take a few more seconds.

[screamn]

maybe need to clean the mass air flow sensor

[Rockettman]

When the a/c compressor comes on, the rpm's should jump up a bit to compensate for the extra load of the compressor.
I would double check the IAC valve. How did you clean it? Was it removed for the cleaning?
Note: my above mention may only be at idle; not at higher rpms. Since your idle is high in the first place; my thoughts may not be correct. If they dropped; that's a different story (which isn't the case).

[Pat]

I removed the IAC and cleaned it with brake cleaner. Wasn't gooked up, just a coat of black carbon soot. Dissolved quickly. I'll clean the MAF as you suggest but I had cleaned it a month or so ago with no ill affects along with the air filter.

[MOTOWN]

cleaning the iac will not always solve the problem, i know there is a lot of talk about "cleaning" it but if its bad its going to need to be replaced.

[Pat]

Well, I replaced the IAC and that seemed to fix the problem. Idle speed is down to where it should be, 700 RPM.

That little part is expensive, $140+ retail, $120 with discount by dealer, who also happens to be a neighbor.

[MOTOWN]

Glad to hear everything worked out for you!

[GetMeMyStogie]

My original IAC failed outright when the plunger, which appears to be Bakelite, cracked and a piece of it actually separated.

[BLACKMARAUDER04]

What does the IAC look like?

[RacerX]

Well, I replaced the IAC and that seemed to fix the problem. Idle speed is down to where it should be, 700 RPM.

That little part is expensive, $140+ retail, $120 with discount by dealer, who also happens to be a neighbor.

WHAAAAATTT??? You can get the Motorcraft nib for $76.00

What does the IAC look like?

[BLACKMARAUDER04]

Motorcraft part number please ( if someone has it handy)?

[RacerX]

Sorry for the delay. Was speaking to Jerry Barnes. Motorcraft part #: CX1781

I've tried the Mach1 on my car and it worked fine: CX1784