mm28302

Hey guys I could use some advice I recently purchased a 2008 F150 with the 4.6. About a week after I bought it I started getting a cyl. 5 misfire. First thing I did was change the coil pack that didn’t help so I had a set of 8 plugs put in shortly after. It still tripped the code for cyl 5 misfire. We swapped injector #6 with #5. It is still persisting. The shop that I have been using seems to think it could be a bent valve or computer issue. So I took it to the dealership they recommended a whole new set of coils I plan on doing that Monday, though I seriously doubt that will fix the problem.

More about the misfire: it always happens when the engine is under a load i.e. Getting on the interstate after it shifts from 2nd or 3rd to the mid rpm range 3000-3500 or pulling a grade at 3000-3500. Of course if I hit passing gear. I’m at a total loss my warranty company will pay for an internal lubricated part of the engine I just don’t want to have to pay for the diagnosis of that if it’s not internal. I know its hard to “diagnose” without seeing the vehicle but I would like some feedback on weather y’all think it could be internal or a computer issue.

JCR 56

If it is a bent valve it will miss all the time, not just when it is under load. I would have taken it back where I bought it when the miss started and told them to fix it or keep the damn thing.