random misfire, 2004 2v 5.4 f150

[swynx]

so 2 years ago my buddys pickup with only 68k got a random misfire, went diagnosed and eventually blew up the engine. he got a loan from the bank and had a shop put a "new" engine in it with a 4 year warranty...

the same week he got the pickup back the same issue started. ive spent the last year helping him on and off replace random parts trying to get this thing fixed.

well take off from his house, drive maybe 4 miles, go thru a few intesections, drive maybe 10 minutes. randomly you will stop at an intersection and it will start running real rough, low idle, in drive. push the brake/gas, it gets better. put it in neutral and it pretty much goes away. stop at the next intersection and it may or may not do it, more often then not if you dont apply gas it will just die.

i have replaced the power steering pressure switch, fuel pump, filter, full tune up. ive unplugged pretty much every sensor i can think of, the injectors are plugged in, pretty sure i smelled the line on the fuel pressure regulator, sprayed starter fluid around, added an extra 5 ft lbs tq to the intake. probably forgetting some stuff.

it has been back to the shop that swapped the engine several times, as well as the ford dealership. in fact the pickup basicaly lives there now, they cant seem to figure it out. and say they cant do live streaming.

any idears? google search shows a bunch of these threads on the f150 forums.

 

[adsm08]

So the dumbasses at your local dealership can't recognize a sticking torque converter clutch when they see it in person. I never should have hung up the wrenches.

 

[swynx]

So the dumbasses at your local dealership can't recognize a sticking torque converter clutch when they see it in person. I never should have hung up the wrenches.

they are the "special" kind of mechanics, that also charge 6500 to swap in a "remanufactured" engine...

shouldnt that cause the problem at every stop tho?

i know almost NOTHING about how automagics work.

obviously the problem only occurs after the drivetrain is warmed up.

also i guess i should have noted that it does throw codes for a random misfire, and occasionally a specific cylinder.

however the pickup is on 35's with stock gears and i was told the guy he bought it from used it in the dunes..

 

[85_Ranger4x4]

also i guess i should have noted that it does throw codes for a random misfire, and occasionally a specific cylinder.

Is it always the same cylinder? Swap the coilpack with a different cylinder and see if the missfire moves with it.

Might check around the spark plugs for moisture, I had a random missfire in my '02 with a 2v 5.4, snow had drifted in thru the wheel well and settled around #7 melted with engine heat and was shorting it out. It never pinned down which one was missfiring, just threw a code for random. I think there are heater hoses that can leak into certain spark plug wells too.

Dad's '05 had tranny shudder, never really seemed like a missfire. I am sure your results may vary on that too though.

F-150 Heritage I take it?

 

[adsm08]

shouldnt that cause the problem at every stop tho?

No, a sticking TCC can be intermittent. It can also set random misfire codes.

The fact that it tries to stall at a stop and perks right up when taken out of gear makes it sound like a TC clutch.

 

[IMenriched]

Gotta wonder if it a faulty relay for the trans? or for either the ignition or the fuel delivery? was the IAC replaced as well?

I'm not saying that it can't be a sticking TC.....with just 68k....wow something is clearly overlooked