Last week I left a stop sign, got up to about 20mph, heard a clunk and engine rpms went way up. No forward gears, still had reverse.

This is a 98 F150 4wd with 4.6L Automatic. 186,000 on it and engine has been running great. Just had a tune up done at 179,000. New plugs, new wires, new o2 sensors. Only issues with truck when I got it with 108,000 have been normal wear out of parts. Replaced exhaust manifolds, alternator, starter and battery.

Went and picked up truck 2 days ago with the new rebuilt tranny and made it about 5 miles from the shop. Hit about 50-55mph and the truck jerks real hard right around the 3rd-4th gear shift. Did it a couple of times on the 10 mile ride home. Tranny shop was closed by then. Had to go to work the next morning but left a message at tranny shop. Drove the 30 miles round trip to work and back and finnaly got it back to the shop this morning. All together I put maybe 60 miles or so on this thing since the rebuild and it jerks and bucks like the wheels are going to fall off at 55mph.

Tranny guy says it sounds like a misfire. It was not doing this before I took it in. No CEL or anything. He plugged it in an found no engine or tranny codes either. It does have a 1 year or 12,000 mile warranty and is sitting at the shop right now.

Anyone have any insight?

 

What brand plugs and wires did you use? Are the coil packs still original?

 

It's whatever the shop put in for wires and plugs when I had it tuned up. That was approx 6-7000 miles ago.

Tranny shop guy says he drove it 15 miles with reader plugged in and when it happened, 3 cyclinders misfired.

It does not lose power or speed when the "jerk" happens. It happens so quick it feels like you are hitting a pothole.

When I did have a misfire, the CEL came on and it would blink while the truck was misfiring, usually while stepping on the gas or at idle and it would do it for roughly 15-20 seconds until you got up to approx 65 MPH.

The coil packs are the same since I have had it, so at least 78,000 miles.

I just find it weird that this problem sounds similar to other TC issues and never occured until the rebuilt went in.

 

I've had F150s that misfired just like you described. No codes set, but I could watch the misfire counter and see it count off misfire events. It did feel just like a pothole. New plugs and/or coils fixed it each time.

 

Better find out what the shop used - if they didn't use Motorcraft plugs that may be your problem. Aftermarket wires are also a crapshoot.

 

i just hit 188,000 had some work done on my rearend and my tranny started downshifting hard from 2nd to 1st.

 

Had the exact same issue with the exact same symptoms on my 2000 F150 4.6l. Misfire on 3 and 4. Replaced all coil packs with a set from global auto on e bay and drove her another 80k without issue before selling her.

 

You don't have coil packs, you have coil on plug (COP). The OP has coil packs and wires.

 

I stand corrected, Coil on Plug