Got a really vexing problem with my '95 with 5.0 and E4OD when it's cold (ambient >50F or so and engine cold). Starts fine, idles great, and then while moving at moderate speeds after a couple of minutes it will start to stumble and buck - sometimes pretty violently. It doesn't feel like a fuel pressure problem, which would not be as abrupt - it feels as if it's cutting the ignition completely out for a split second randomly. After it warms up, it performs flawlessly. Both KOEO and KOER tests come back with 111. While trying to chase this down, I've replaced everything in the ignition system except the coil (I know, someone will say, "Well, why don't you change it also?" but I don't see how it could be the problem - but that's probably next by default!). I've replaced the Engine Coolant Temperature sensor (fixed an occasional non-start when cold but didn't fix this other problem). Over the last year for one reason or another, I've rebuilt the EGR valve and replaced the actuator and feedback sensor, and replaced the idle air valve and the purge canister solenoid valve. New fuel and air filters, fuel pressure looks good when I put a gauge on it in the driveway but don't have a way to monitor it when driving. No backpressure in the converters; manifold vacuum is steady and right. Anybody had this experience? Could the problem be in the transmission controls - like lockup converter kicking in and out for some random reason? I appreciate any good ideas y'all might have.

Thanks!
Jackson

 

Just curious, how did you rebuild the EGR?

 

I soaked the valve area in Chemtool while exercising the valve with a hand vacuum pump until it had freed up, and then used an old toothbrush and cotton swabs to get out the last of the residual gunk. It cleaned up just like new and has worked fine ever since. I also took out the feedback pot (held onto the top with three small bolts on mine) and checked inside for cracks, leaks or miscellaneous junk. There wasn't any so I just bolted it back together. I did find that the passage between the valve and the intake manifold was pretty heavily carboned up so I used a shop vac and a small screwdriver to remove all the buildup and suck it out of the manifold instead of allowing it to fall inside.

 

My 90 did the same thing. It would buck like crazy when in OD and the rpms got below 1200. At times even in 'D' and low rpms it would buck. It turned out to be a bad pressure switch in the transmission. One of the transmission guys who works on a lot of the Fords, found it. It was readily available in aftermarket so it has replacement value. It hasn't done it since that was replaced. My trans was the AOD 4x4. Yours is an E4OD I believe. They also use the same type switch.

 

Thanks for the tip about the switch in the transmission, AK. I realized after I posted this that it really is in the wrong forum - the truck is a '95, then I realized that there's another thread like this from a guy with a '97 that's having a similar problem. Both have the E4OD, but of course our engine management systems are totally different, as is the engine itself, so that lends some credence to the idea this is a trans problem and not an engine problem.

Jackson