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Showing results for tags '4.0l misfire'.
random, intermittent #1 cylinder misfire. I have replaced the coil-pac, #1 injector, spark plugs, and both upstream O2 sensors. engine leakdown and compression normal though #1 slightly lower in compression. emissions always meet I/M standards (no certificate of waiver needed). have all heat shields including #3 injector so vapor lock not issue. engine runs good when not misfiring though does have a slight roughness noticeable when at idle. Is there any way to check the current of an injector wire or plug while engine is running and showing symptoms to see if all is well in the wiring harness? engine bay is quite clean for 235k mi. and no noticeable damage to wiring harness, but there could be a partial open in a circuit I suppose. Any ideas? don't know where to go from here with repairs/diagnosis etc. Oh, misfire occurs mostly after engine has been under normal-use-load for a couple hours or so, but not always. sometimes it is misfiring at cold-start.