2003 Ranger Rough Idle at stops.

[Fordtruckman80]

For those who don't like to read long posts, i'll post my question first, and then the history after. My 2003 Ranger with the 3.0 and an Auto transmission is running rough at stops. The idle has been fluctuating between 500-800, usually around 600. Usually it's at 850. Today at a stoplight it jumped to 2K rpm, all by itself. It then dipped down to 500. The truck runs great when i'm moving, it just hates to idle. Also, it seems the idle raises when the A/C compressor clutch cycles on.


Now for the history. A month or so ago, the truck was having a problem idling. It would dip between 300-600, and couldn't hold the idle steady. Whenever it hit 400, it would start to sputter, and a few times it quit on me. Took it to the dealership where I got it, and they referred me to their mechanic. He did a diag on it, and all he found was that the IAC was overexerting itself. He happened to have another 3.0 Ranger at the shop that was for sale by the same dealer. We swapped the IAC from the other Ranger onto mine, and the problem went away. That seemed to work for about a month. Then this morning on the way to school, I noticed the idle was around 600, which was lower than usual. It was fluctuating between 600-800. It wasn't trying to stall or anything else though. It ran fine as I was leaving school, and did perfect until I got to a Stoplight. That's when it got worse.

All help is greatly appreciated. Thanks in advance guys!

 

[lorenambrose]

MAF sensor or TPS would be my guess. Both can be checked with a multimeter very quickly. A Haynes manual will give you all the specifications. I would start with the TPS.

 

[Bryan22]

maybe the used IAC was no better than yours. try just cleaning it before spending the money to replace it. gaskets are cheap.

 

[Fordtruckman80]

Thanks for the replies guys.

I took a little ride, and I noticed that the problem occurs when the A/C Compressor clutch cycles on and off. For example:

First Click cycle - Idle dips to 500
Second Click - Idle raises to 850
Third Click - Idle drops to 500
Fourth Click - Idle raises to 850.

Since it only happens when the A/C is cycling and putting a load on the engine, i'm quite sure it's the IAC again.

I'm gonna try cleaning it, and see where that gets me for now. Ultimately though, i'll be getting one of the nice new Motorcraft ones.