Hi everyone! First post.

1996 4X4 F150 XLT 351M Auto Transmission 129K miles.

Without rambling on too much with what will likely be confusing info. I will try to describe the problem. Truck bucks and misses at 1800 rpm's after shifting into overdrive. If I turn the overdrive off and run @ 2500 rpm's the engine runs great. I have changed the range sensor on the tranny, replaced the solenoid starter relay (click issue), and new Motorcraft plug wires. New plugs. New fuel pump. New fuel pressure sensor. Misc. other electrical components This problem is becoming very frustrating as the idle miss can be remedied by changing the timing. It will purr then but the highway test is as described above with the rpm issue. Why does it run fine @2500 rpm's? This seems to rule out many potential problems. I am about to pull my hair out. Any advice would be greatly appreciated.

 

Could be the torque converter. Just my guess.

 

What lead you to replace those parts? Did you check for codes leading you to the parts replacement?

 

Are the plug wires well separated? Could be a cross fire issue. From my experience these engines give a little shake at idle, not smooth like the 5.0L. Mine has always done that & never been an issue.

Torque converter shudder may be what your experiencing. I don't know much about that other than it can happen, especially if the truck has towed heavy.. I have essentially the same truck with 216k and original tranny, and it hasn't had the easiest life, so I would be surprised if yours has serious issues already.

Those with more knowledge will chime in soon.

 

my 94 aero star bucked really bad in overdrive. a major tune up cured it. wires, cap, rotor, plugs.

 

Vacuum leak?

 

If the torque converter was hanging up I shouldn't be able to enable/disable overdrive should I? I live in a rural area so I haven't had a code read done yet. How about a plugged injector? If so why good performance @ higher rpm? The other day I pulled a medium load (aluminum fishing boat) approx. 35 miles. I turned the O.D. off and ran at 2500 rpm with smooth results. On the way home the truck performed flawlessly in O.D. (1800 rpm). This is what puzzles me. Why is the truck experiencing this performance flop?

 

Clean the MAF sensor. A dirty one can make it seem like other problems are happening.