Truck slipping when engine is bogged down in overdrive.
I bought a 2004 F150 super-crew cab v8 5.4l a year ago. I had it about 2 months and the transmission and torque converter went out in it. The shop repaired the transmission and replaced the torque converter, drove away and truck was bucking real bad, took it back to the shop and they said it was a bad torque converter so they replaced it again. I drove for about 6 months with no problems. Now every time i am going about 50 mph then i push in the gas about half way, the engine bogs down and it feels like the transmission is slipping and it feels as if the back end is hopping up and down. Once i slam the pedal down it will finally down shift and it goes away until the overdrive kicks back in and i go through the same thing again. I took it to a shop they replaced the feul filter and said there was nothing wrong with the transmission. but it is still doing this. It gets worse the faster i am driving. If anyone has any suggestions please let me know?? Thank You.
RE: Truck slipping when engine is bogged down in overdrive
I have a 2004 F150 extended cab with the same problem except it doesn't feel like the back end is hopping for me. I've noticed that the issue happens when the truck is bogged down and I apply constant acceleration - at about the 1700 - 2000 RPM range while the truck is at normal operating temperature. The truck will shift ok if I press the pedal down. While driving with overdrive off, I've noticed the same issue so I'm thinking it's not the transmission. I've read it could be the coil over packs (COP), and wonder if it might also be either the TPS, MAF, or EGR? I have no check engine light lit, nor does it light when the problem occurs. Also, sometimes if I gently press the gas just enough to accelerate without downshifting, the truck "snaps/lunges" forward slightly as if the throttle plate opened all of a sudden, and the bogging issue goes away. Has anyone had this problem and fixed it? Would appreciate any info, thoughts, ideas before I start ripping out sensors one-by-one.
I have talked to quite a few Ford mechanics and everyone one of them has said it was an engine misfire, and they have only seen a select few of vehicles that didn't throw a misfire code. I bought a diagnostic scanner thinking i might see something but no luck. It started raining here where i live today and it seems like it is twice as bad as it was yesterday so My next thing i will be trying is changing out each coil pack until i find one that fixes it. Ill keep updating the forum.
I've noticed the exact same behavior - worse when there's humidity in the air. I also tried a scan tool to see if for some reason there was a code with no check engine light, but the ECU was clean. Intereting if it's a coil pack and it doesn't trigger a misfire. Where'd you buy your COPs?
Niether one of you two has said how many miles your trucks have. But if it's not bad boots I would bet on plugs before cop's. It seems to me that if a coil fails, it fails. But a plug will work okay untill you put it under stress. Just an idea.
Mine has 92k miles. I bought it used with 77k miles about 1 year ago. I've changed the plugs with no luck, used OEM Motorcraft plugs. I bought the truck with a "home-made" intake, so I took that out and installed a K&N FIPK intake. I've also re-programmed the truck with a SuperChips tune that supports the intake. Today I changed the fuel filter, and one of the COPs, but did not get a chance to test drive the truck. When I do, I'll post the results. I'm also going to see if I change the TPS later next week. I measured resistance with a meter today and found it fluctuated a bit towards each end as I turned it with a screwdriver.