Hi All - have a strange issue on my E350 I was hoping to get some help on...

So essentially there is a stumble/miss at idle - whether it is cold or warmed up. It runs smooth for maybe 5 or 10 seconds then there is a stumble, repeat... Its enough a stumble to be noticeable and it is not present when the RPMs are up - like during cruising. Occasionally if I lightly press the gas it will stumble slightly before it revs up and the stumble vanishes. One time it stalled after it I shifted it into reverse - this was after some highway driving and was plenty warm. There are no codes...

The distributor/ignition module was replaced by previous owner 2 years ago. I recently did plugs and wires - all motorcraft OEM (including distributor)..

Does this sound like a vacuum issue? Any ideas...?

 

Here was an interesting find with this problem.
https://www.ford-trucks.com/forums/3...e-in-idle.html
Otherwise I would look into cleaning a sticking IAC or maybe carbon in the EGR valve.
jim

 

Thanks for the links. Those seem to be small blocks but it could be applicable to me.

I'm reluctant to think its the IAC - as its not surging/revving at idle - which is common with a sticking or failed IAC. I'm going to start with a fuel filter and EGR valve replacement... see if that does anything. Just hate throwing parts at a problem haha..