onetouch99

I have a F150 XLT 2005 5.4. It has 145 k on it, a hypertech II chip, the plugs were replaced at 100k. it also has a Trueflow intake.
When driving between 40 and 50 mi per hour the engine will buck like it has a mis fire. It will only happen when I accelerate once I am going this speed (under load). This may happen once or it may happen several times in a row. If I turn the over drive off it won't buck. I have also had it happen at higher speeds but consistently at 40 to 50 mi.
The frustrating part is what I've done about it so far. By the way this has been going on for 8 months or so.
1. Took it to a Dyno shop. Diagnosis change all plugs and coils. Didn't sound right to me since they couldn't tell me which cylinder was misfiring so I didn't do it.
2. Took it to a Ford dealer. They did power and mode 6 tests on it. They showed misfires on 2,4,3,8, and it bounced around though. they replaced coils 2 and 4. bucking stopped for 1 day then started back up again.
3. Took it to another private shop. They said it was starving for fuel at high end showed lean codes, and plug 2 was arking through the boot. They replaced the Fuel pump, filter, one plug, one boot. Said they think they have fixed it. drove away..... problem not fixed. Took it back to the shop, Told them to put my old fuel pump back in and continue to diagnose. While driving to the shop that day the check engine light came on. The shop documented the following:
P0430 Cat efficiency Bank 2
No Misfire codes no counters in mode 6
Removed pre and post O2 sensors on each Bank to chech back preasure Verified Bank 2 (Passenger side) Restricted and Bank 1 starting the same.
Their Recommendation: Replace both Cats. Cost: $4700.00 California..... Only dealer cats.
I didn't go for that as my truck has 145k on it. So I had a buddy of mine cut off the cats and visually inspect them. Bank 2 - restricted, Bank 1 Fine. I had him put a srtaight pipe in place of the cat. Suprise Suprise, The bucking problem is still there.

Not sure where to go from here.

Thanks for any help on this as it is very frustrating to take youe vehicle to a "professional" several of them and you don't get results.

pinkham

my truck started doing the same thing last month, I didn't think about it being a mis-fire, I just thought it was a tranny issue. took it to a tranny shop today they said it was the torque converter slipping?? I'm wondering if it really is the problem myself....I also have a hi-flow intake on it.

fordefonefifty

since you have an intake and a chip it will probably throw off your fuel mixture so i would look at the fuel pressure regulator on the fuel rail and maybe some octane booster. also who knows maybe your fuel injectors are dirty.

LMichels

My 2003 just started doing the exact same thing you are describing. About to start the fun process of diagnosing... Guess i'll start with the basics and go from there.

mjlater

My truck is doing the exact same thing. Only mis fires when gently rolling into throttle while going 40-50 mph. Ive been told its the COPS or wires. I also get the p0430 bank 2. Ive got a pretty good exhaust leak on that side. Do you have an exhaust leak too?

LMichels

No exhaust leak here. Just changed the fuel filter and seemed to fix the missing at idle speeds. I'm still getting the shuttering at 50-60 mph under slight acceleration. I guess the next step is to check the COPS?

mjlater

Everyone that I have talked to and most of the threads I've read about this topic have all pointed to the COPs. When I get some time I'm ordering all new plugs, COPs, and boots. Might as well. I've learned to drive around that sweet spot where my trcuk surges. Keep us posted.

getsynyster

It probably is running lean if you've got an after market cai or exhaust on it and it's not custom tuned. 05's came from the factory just borderline lean, so that's probably it.

closrockwell

I have researching this and it all points to cops. They have been a pain in the rear. I started having issues with them since 90K. I am now at 135K and have not found a reason why they keep burning out. Some of the reasons out there are either a fulty plug or PCM. The dealer changed plugs and cops under waranty. Then I had the problem again and changed all plugs and wires at 110K. Just recently I started feeling the bucking. I will post once I have solved the mistery of why the cops keep failing. (problem only comes up when in overdrive or when it is under a heavier load and rpms are low.)

LMichels

Took mine in to get diagnosed and it was the #5 coil. They wanted 200 bucks to change it so I went and bought one for $70 and changed it myself in 10 minutes. Luckily the #5 is easy to get to. Runs great now!