Ford Misfires Shakes and Generally Runs Bad
DennisB WiseAutoTools.com © Summary: DenLors Tools and Wise Auto Tools specializes in automotive tool sales. However, sometimes we get questions on auto/truck repair unrelated to any specific tools. One of the most common problems with Ford F150’s is blown spark plugs. The aluminum threads fail, ejecting the spark plug breaking the coil on the way out. We sell thread repair kits that work right over the fender. In fact our thread repair kits fix “parts store kits” failed repairs. I believe this is something different. Below is a question from a Ford F150 owner about a drivability issue.
Question – Well I have a 2002 5.4 Lariat F150. It has around 130,000 miles and just in the last couple months I have blown 3 coil packs and spark plugs. I just had a tune up a little over a week ago and the problem is still there. I’m losing power and my truck is I guess you could say is “missing”. When I go to give it some gas it starts shaking the whole truck. Just wondering if I can replace the heads and the problem goes away or is there more to it that I have to do? Would like to try fix problem because I really like the truck. Just need some answers on prices of what could be done or if I should just trade it off and get new truck. Would like an answer fast the problem isn’t getting any better. And by the way I took it to a local ford place for tune up said two plugs had oil all over them.
Answer – Let me try to help even though I’m at a clear disadvantage because I can’t check the vehicle in any way myself. A mechanic that can drive it, hear it and test it would be more likely to help you.
On the F150, blown spark plugs usually means the spark plug threads have failed causing the plugs to physically eject, breaking the coils. See our Ford Spark Plug Blow Out FIX thread repair article for more on that. When you say you’ve blown 3 coil packs and spark plugs, I’m assuming the spark plugs did not shoot out of the head and they for some reason just “failed” causing misfire codes. You don’t say if replacing them actually helped or not. I’ll assume that since you had a tune up a week ago and the truck still runs bad that maybe the coils weren’t bad and there was a different problem that went un-diagnosed. Misfire codes may take awhile to set because a certain number of misfires must be reached before the light will come on and a code stored. Using Mode 6 to check a misfire counter, a good tech with a proper scan tool can like a Genisys Encore, can see which cylinders have a problem. If it’s one or two cylinders, it’s possible there could be a compression issue caused by something mechanical like valves or piston rings. Could be bad spark plugs or coils (which you’ve eliminated) or faulty fuel injectors. If it’s a valve issue, then a valve job should fix the problem. If it’s a piston ring issue then a rebuild should be considered. I would do a compression test and a cylinder leak down test to check the mechanical integrity of the engine before throwing more parts at the problem.
If you have more than 3 cylinders misfiring, there could be a timing issue – maybe jumped timing. A jumped tooth on a timing chain sprocket can make all cylinders misfire setting a P0300 random misfire, fault code. There are many things that can cause a vehicle to run bad though- A clogged catalytic converter could cause issues especially when accelerating because the exhaust has nowhere to go and chokes the engine. A crank sensor may not be registering all the time, fooling the computer by giving false RPM data. A fuel pump may not provide enough pressure and will cause the needed amount of fuel to be absent, making the engine misfire or stall. And the list goes on.
The mention of oil on the spark plugs – having oil all over them, could be valve cover gaskets if the Ford dealer was talking about on the outside of the plugs or could be bad valves, valve guides or piston rings if they meant oil was on the electrodes of the spark plugs. This would be evidence of burning oil. BTW if it’s burning a lot of oil you would already know there’s an issue because you would have been adding a lot between oil changes. If it’s not leaking oil externally, then it’s burning it.
Basically, a local technician can use all of his senses, experience and tools to evaluate the vehicle for you and provide a recommendation. He will also be able to provide estimates for the repair after a correct diagnosis has been determined. Good Luck.