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Hi everyone, I am looking for good direction with this misfire. The previous tech has replaced the spark plugs and moved the coils, but with no success. The misfire is non existent on #5 while test driving, but just a a few random misfires on the other bank. During start up is when the #5 will misfire and then go away. Spark plug does not look fouled by fuel or oil, but I am still not ruling out a fuel or oil issue. What do you guys think? Ways to test the port injectors without having to remove them?
This one that the symptoms narrow down the list of prime suspects
(1) Sticking fuel injector
(2) Sticking valve or hydraulic lifter
You could try listen for each injector open and closing by hold a stout screwdriver firmly against each injector and using it as stephoscope. This test can be misleading as you will hear all the injectors in the fuel rail not just the one you are diagnosing
Hydraulic lifter jack can happen on some engines if the wrong oil grade is used.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
I second the head gasket suggestion. Happens occasionally with these 3.5L engines.
If you don't have a borescope, you can also install a leak down tester and dial it up to full pressure while checking for bubbles in the cooling system. Do it with the engine hot AND cold to be certain. Any bubbles mean a failure.
Hey guys, quick updated. Head Gasket is leaking! Quick cylinder pressure test when cold did not show any bubbles in the coolant, but once warmed up I removed the rad cap to see bubbles and combustion gas. I did the pressure test once more when hot and confirmed gasket failure with bubbles in the coolant. Thanks guys.
