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I have a 2001 Dodge Durango with the 4.7 liter V8. I recently changed the spark plugs and it ran for a few days misfiring periodically. Then overnight after a good day of running it would not start. The engine will rotate but not fire. I changed the individual coils but only to get the same result. I think that I may have the wrong spark plugs but need advice on where to go next. Please help. Jared

Did you keep the old plugs? If so, pull one of the new ones and compare them, particularly the length of the threads.

It’s best to stick to the same plug brand and part # as came from the factory.
(unless the engine has had serious modification)

Also, have you checked the plug gap? Even if they’re “pre-gapped,” the slightest little tap in the box during shipping can shorten the gap and screw things up. Check that too.

Why do you think you have the wrong plugs?

Are you sure it’s spark that you are lacking?? How did you determine that?

Yes I have done all of those things. I followed along in the book and performed all of the tests on the coil packs but I have not been able to test the sensors. One person told me that it could be the timing but that is controlled by the PCM. At the moment I am trying to get my hands on a code reader and maybe that can help me get closer.

Was it running fine before you changed the plugs? If it was, than your suspicion is correct…you’ve used the wrong plugs. If they’re different enough they could conceivably cause a total spark failure, although that would be unusual.

Your next step would be to get the proper OEM replacement plugs and replace whatever you put in.

If it was not and that’s the reason you put in the new plugs, you may have a crank position sensor failing. See if you have spark when you try to start it.