Surging forward on its own at idle in drive

[searcherrr]

In January I replaced the CPS. Here: http://www.automotiveforums.com/vbul....php?t=1084861

What else would cause surging forward? CKP ?

The CEL is on, but I haven't been around the van (family is borrowing it since their cars flooded from Hurricane Isaac; which I cannot believe is almost a year ago now 8/29/2012) to check the code myself. In the past the CEL was cylinder 5 misfire. Replacing the CPS seemed to fix "most of the surging forward" issues... along with hot start problems, but that didn't last long and these issues seemed to have become more frequent again now. Recently it stalled one time at idle immediately following a startup... the next successive startup after it stalled gave it a "whoosh" rev in RPMs..... sorry thats the best I can describe it as right now.

FYI - Have to stomp the brakes to keep the van from wrecking into other parked cars or our garage wall when it surges forward on its own.

Also, van seems to misfire predictably on startup when its been very humid or raining outside. I am not sure this is related and I think its not... I think the humid/wet issue correlates to the occasional cylinder 5 misfire issue.

[northern piper]

well... I'd start by pulling the code. No sense guessing without knowing what it's telling you.

[scubacat]

ditto. pull that code and post it; we're here to help!

[12Ounce]

All the clues you have given up to now point to a huge air leak ... possible somewhere around/in the brake booster.

[searcherrr]

Ok, the code is cylinder 5 misfire as I suspected. I have them keeping the van in the garage (out of much rain there lately) till I can work on it again.

What about cleaning the MAF/MAS ?

IAC has been replaced and cleaned in the past.

Huge air leak??? Intake manifold? I ask because its always been cylinder 5.

Could the crank sensor do this? I don't believe its ever been replaced and the van is at like 160k I think now.

[12Ounce]

Maybe I'm reading too much into "surging" .... that always makes me think first of air leaks. But there are other things.

I have a hard time remembering all that has been done to the vehicle. Have the intake isolator bolts been replaced? ... at the same time clearing the EGR ports? That would be next on my list.

Then the plugs, cables and coil pack. Yes, cleaning the MAF sensor would be an easy next step also .....

I do not think the crank sensor would give "surging", and it certainly would not specify a particular cylinder ... I do not think!

[searcherrr]

When I say surging... i just basically mean that the van lunges forward on its own... as if it was surging UP RPMs on its own without pushing the gas down.

[12Ounce]

Hmmm. Is the throttle plate moving during all of this? Take all the cables loose from the throttle body ... if it still happens, its probably a crazy IAC valve ...???