there have been many threads about idle problems, but i think mine may be different.

My engine, 4.6L in a 97 4x4, will hold its idle without any change in rpm, but every once in a while i has a violent shudder that can be felt throughout the truck. Usually they come in spurts....like one every 5 seconds and then nothing for a few days.

Also, any time the truck is under minimal load (accelerating from like 30 + or going up a hill) the truck will shake and will not accelerate unless I floor it.

I have the atf draining overnight, if for no other reason that it needed it. I checked the vacuum hoses pretty well and found nothing. I figure I will also put in new plugs. Any other ideas as to what it could be?

Thanks...

 

I had a similar problem going up hills, lost acceloration, but I had a check engine light on too. I don't know if you're Check Engine Light is on or not, but this might help you out...
it's possible without the check engine light that your throttle sensor is on the verge of going. It's a quick & easy fix, part costs $38 at auto zone. Hope this helps.

 

Thanks. Im going to check and see if there is any way to check the sensor in my repair manual. I have no CEL and no codes though.

 

I have the same exact problem as you described going on currently with my Expedition it has got progressively worse though, I have it in the shop right now and they kept it over night so I'm going to find out what it is tomorrow.

Last I heard they found that one of the cylinders was not firing correctly so last thing I OK'd them to do was check compression and the COP and boot.

Guess I will see tomorrow so far I'm in it around $144 just for Diagnostics. ($79 at first $65 compression and all else).

I am seriously praying it's not going to be to much over $300 once they are done!