Stumble/Hesitaion From Idle

[Kamjon]

Have a stock 01 Explorer Sport (not Trac) 4.0L OHC with 120K+ miles. When I bought it at 115K, I knew the cam chains and tensioners needed replacing, which I immediately did. It runs fine, with no performance problems at all.

Problem I am having is that it falters/hesitates/stumbles from idle, but only about once every month or so. This always occurs with a fully warmed up engine. This would not be much of a problem, but it seems to occur only after I have decelerated and stopped at a light. Engine just cuts off for a little less than a second, but it seems a lot longer in the middle of an intersection. Once it died but immediately started right up.

The fuel pump recently quit and was replaced, but has not affected the problem.

The throttle position sensor ohms out good, and the IAC has been cleaned.

Any suggestion? Thanks, John

 

[fixxxer]

Have you checked/cleaned the MAF sensor? Merely checking the resistance of the TPS won't give you the complete picture, especially if there is a weak or "dead" spot on the TPS

 

[Kamjon]

No, I haven't checked the MAF but I will. I'm guessing the TPS may be intermittent and probably needs replacing. Thanks for the reply.

 

[fixxxer]

Before replacing something as expensive as the TPS, check for a bad or intermittant connection to the TPS by wiggling the connector and wiring harness starting right at the TPS and working your way back to the point that it is either inaccessable or joins the rest of the wires in the wire loom. When you checked the TPS, were you using a digital multimeter (DMM) or an analog meter (w/a needle movement)? The analog meters are best for checking for a bad spot, you will get a nice smooth needle movement then the needle will dip when it hits a possible bad spot. I know that you can get small/inexpensive analog meters at Radio Shack for under $20

 

[Kamjon]

I was using a DMM, but mine has a sliding scale at the bottom to simulate an analog movement. I probably ran it through 50 or more times, but I'll check it again and give the wiring a good going over. Thanks

 

[zborntoride]

I was just having the same problem....except for when my truck was hot and i started it up....the idle would move form 2000 RPM to 500 RPM. I checked every sensor....all checked out within spec. The TPS ended up being my problem. It tested within spec....but that didnt mean that there still wasnt something wrong with it. Went to auto zone.....only costed $26.99 plus tax. Havent had a problem since......so just something to look at.