99 F-350 7.3L. Auto 285,000 miles. Driving it down the road this morning (35-40MPH) the truck started bucking and thrashing, motor seemed to be running on 4 cylinders. Even after I stopped and popped the hood the engine was rocking in the truck. Finally shut it off and let it rest for 15 min, restarted it and it seemed to run fine until a I put it in gear. Luckily there was a diesel shop across the street and they hooked it up to the diagnostic tool. There was a CPS error that came up, he cleared it, we took it for a drive truck was running fine until I put it in drive, then it started to buck again, we hit the overdrive button and it stopped and ran fine. Now I have had a constant driveline vibration for a couple of months thought it was the tires that I should have rotated sooner than I did, then I found a bad U-joint 2 weeks ago and fixed it but the vibration didn't subside. Now the mechanic said that it was most likely the tranny and converter????????? He said the while in OD the clutches were locking up yet during the test drive (hooked up to his diagnostic tool) it showed that when we didn't have it in OD the tranny was not locking up?????????
Now this is the 3rd tranny in under 100,000 miles, last was a Ford factory rebuild that was put in 12 months ago at 247,135 with 3 yr 75,000 mile warranty.
Off to Ford I go. (no issues) (40 miles)
Now the dealer takes a test drive and replaced the CPS but no other problems other than still a vibration which they will look at tomorrow.
I have had the CPS changed twice before and both times the CPS is a GO or NO GO item. Does the bucking sound like a CPS or could the vibration and the bucking be clutches and converter problems?
I just want to get this project done here in DC so I can get back to WI and pick up my 08 Lariat that is sitting at the dealer.
Motor has always ran like a top.

 

Kory, if it was me working on your truck, I would check the connections going to the valve cover. There is a problem with the wireing inside the VC that comes loose and makes the truck run ruff. But there is a lot of thing that could cause this problem.

Good luck.

 

Thanks, Dealer here in DC has truck for now. Find out what they have to say tomorrow. Just had the Covers off in Dec. for new Glow Plugs but never messed with the inner plugs and the outer plugs were the first thing I checked when I pulled over.
Wouldn't loose plugs kick off the CEL or at least leave a code of some sort?

 

Yeah, Kory, I would see what they say or find and go from there.

Hope it comes out good.