2001 v6 140k
This morning started and ran fine until I got to ~40mph then started running rough. Problem seems to be only when under acceleration. Idles good and shifts good. Replaced throttle position sensor a while back. No check engine lights on. Any help appreciated. Thx

 

Possible cylinder misfire?.. have you swapped out the engine coils and spark plugs? Suprised at no check engine light though.

 

Had the same problem on a 01 explorer. Changed the plugs and it fixed the problem. It also never through a check engine light. I'd get it hooked up and see what cylinder is misfiring or what is going on.

 

Since your motor has a central coil pack, not individual ones, you may have shorting in the coil, under a load. Also check the plug wires. Under a load they can arc across lines and give you rough running

 

Thx for help. Changed plugs and fixed problem....sort of. First of all....I baby this ol girl and never run hard or even hit passing gear. Today, after changing plugs, I got on it hard to see if still missing and it and found that it misses pretty bad while under heavy acceleration. But.....perfectly normal if putting around. I think...given the way I drive, I just never noticed a problem which has probably existed a long time. Wondering if maybe fuel related.....Should I try injector cleaner? Or bite $80 coil pack bullet? Thx much

 

If I where you I'd have it hooked up and see what's going on before you start spending money. You could end up buying that and it not be the problem. You don't need to throw a cel in order to figure out what's going on. I have my diagnostics testing on my laptop and just plug in and take it for a drive and I see what's going on. Most dealerships have the same equipment, and some parts stores do to and they'll test for free.