Intermittent rough idle

[Falcon_LS]

'99 Explorer Eddie Bauer with the 4.0L SOHC and 71k miles on the clock.

When you come to a complete stop, the engine's smooth as ever. Give it 15 seconds or so, it starts idling a bit rough, perhaps a bit like a valve not doing its job properly. Throw it in neutral, and the vibration's more noticeable. No complaints with acceleration or regular driving.

Plugs and wires are new Motorcrafts, MAF sensor's cleaned, new Motorcraft fuel filter and IAC, new OE intake manifold gaskets. Injector issues perhaps, or build up on the backs of the valves? Thanks!

 

[AKhan87]

Run redline fuel system cleaner and report back

 

[Olas]

My bet is a coil starting to break down and you only notice with excess heat

 

[Falcon_LS]

Originally Posted By: 01_celica_gt
Run redline fuel system cleaner and report back


Got some 3M Fuel System Cleaner in there right now actually, will see how it goes.

Originally Posted By: Olas
My bet is a coil starting to break down and you only notice with excess heat


Although this application is not equipped with a COP ignition system, it does have a single ignition coil to which all the wires are connected. Could possibly be the coil, not sure. It does smell a bit like it is running rich.

Also worth mentioning - there are no codes stored in the PCM.

 

[Merkava_4]

EGR valve might not be closing all the way, letting exhaust dilute the already lean idle mixture.

 

[Oldmoparguy1]

Originally Posted By: Merkava_4
EGR valve might not be closing all the way, letting exhaust dilute the already lean idle mixture.

^ That, or a small vacuum leak.

 

[Vikas]

can you check the fuel trims?

 

[Falcon_LS]

Thanks for the input.

Haven't checked the fuel trims just yet, but the PCV valve and elbow seem to be a common culprit on these for vacuum leaks, and I'm going to address those first, then pull the EGR valve off to take a look at it.