2008 explorer misfire

ford
explorer

#1

cylinder 2 misfire. already replaced the ignition coil, spark plugs, plug wires, fuel pressure regulator, fuel inector, had a compression test run results were normal. took to dealer they wanted $600 to check the valve springs I didnt have the money at the time didnt know if that could be the cause or not im all out of ideas


#2

which engine?


#3

the 4.0 sorry


#4

Well that indeed is a dilemma. It seems like you’ve pretty much replaced or tested everything that would be a typical misfire cause. hmm … for a firing to work correctly these things have to all be in place inside the cylinder

  • proper amount of air and fuel, at the correct ratio
  • good, healthy spark at the tip of the spark plug
  • the spark needs to occur at the right time, the proper number of degrees before tdc on the compression stroke
  • good compression

I’d probably start with compression, rail fuel pressure, and visible spark quality test.


#5

Since your ignition coil fires two cylinders at a time, and you have a single misfire, have replaced plugs and wires, I would tend to believe the problem is most likely elsewhere. That’s assuming new parts are good. I would be checking for injector pulse next, which means you need a noid light. Do not use a test light as they draw too much and could possibly burn up the PCM. With noid light connected on #2 injector connector, it should flicker in rhythm to the misfire. If not, then there’s either a problem with the wiring or the PCM.


#6

and if it does flicker in rhythm with the misfire?


#7

If the noid light when hooked to cylinder 2 injector looks the same as it does when hooked to any of the non misfiring cylinders then the problem is not with the injectors or the pcms control of the injectors or the wiring to them.

If the noid light acts differently , then the misfire is caused by the injector, fuel pressure to the injector or the pcm, or wires to the injector.


#8

okay thank you


#9

i should have said this from the beginning its an intermittent misfire and i mean completely random misfire, anyway that being said i did the noid light test by waiting till the engine started to misfire and then plugged in the noid light and the light did not illuminate for about a minute and then started to flash like normal so i am assuming its something with the wiring or the pcm


#10

If it does flicker in time with the misfire, then your problem is most likely going to be mechanical. As in valve spring, lifter, camshaft, intake gasket, rag dropped in the intake. And yes, I have seen the results of a shop rag dropped in an intake. Had a dead miss that was very hard for the “tech” to figure out as we never goof. A vacuum gauge would be a good tool for this one. A misfire that is caused by a mechanical problem will make the needle bounce instead of a steady vacuum reading.