Humming and Skipping at high speeds

[gobucks]

We have a 2002 Ford Explorer that has been humming/vibration and then skipping (bucks) at high speeds (above 45) mph.

First got a tune-up, drove it for two hours to our destination with no problems. Thought it was fixed. "Easy cheap fix" I said. Spoke too soon. Coming home it started again.

Check engine light came on, code was for the EGR Sensor, which was replaced. Problem still exists.

Our mechanic has been on the phone with the Ford techs. They have not heard anything like this. Suggested replacing the crank sensor. Problem still exists.

Worse when engine is warm. Does not exist when engine is cold.

While driving, engine will just start to hum, then there is a skip. Kind of feels like "trailering" when the car starts, the the trailer starts and there is that "miss". Does not occur at lower speeds. Hum is about 3-5 seconds before the skip.

It doesn't appear that the engine is missing or slowing down according the tachometer. The tachometer remains constant.

Truck has about 106,000 miles.

Any ideas? We're all stumped.

 

[rodav8]

Do you get an ABS light occasionally? Or have the 4WD light blink? If you do, and if your Exploder is equipped with a single Rear speed sensor on the top of your rear pumpkin, then THAT is your problem. I had that same problem with mine and after I had changed the speed sensor, I haven't had that problem since!! I still haven't figured out WHY that was the problem, but after someone on here told me to test it on a dirt raod with the 4wd engaged and see if it happened...it tried it and it didn't do it. In fact a drove it on a rainy day for about 50 miles on the highway and it didn't do it. That poster said he thought the 4wd was trying to engage. I took it to the local Ford dealer and told them EVERYTHING and they told me they couldn't find anything other than two codes for the rear speed sensor. The codes were C1165 and C1175. So, I figured, wth, so I changed the sensor. It was $49 at AutoZone. Took me 10 min to change it. So, try putting it in 4wd on a rainy day and see if you can duplicate the gripe.

Hope this helps!!!

 

[gobucks]

Thanks...will check that out. Makes sense. It sounds like the 4wd is engaging at that speed. Will let you know what happens when I change out the speed sensor.