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2005 Cadillac engine misses it is not spark plug or coil
2005 Cadillac engine misses it is not spark plug or coil problem no vacuum above the cover can a vacuum leak below the intake cover be the cause ? what is the cover called over the intake manifold Plenium ? Plugs and coils have been replaced it still misses misfires at idle as well as at higher RPM
You have proved your misfire is not ignition related.
That leaves compression and fuel.
Do you now want to gain access the the injectors and listen to them with stethoscope etc?
Does your engine have AFM or DOD, Displacement on Demand (8cyl to 4cyl mode for cruising)?
asked if the misfire could be caused by a vacuum leak under the intake cover all other vacuum lines have been checked except under the cover pleneum cover? don't know what it is called can one bad coil be replaced on the 32 valve northstar or do all 4 coils on one side need to be replaced?? I did not get an answer to this question
If it misfires at high rpm as well as idle, it will not be a vacuum leak.
You said it is not the coil or spark plug.
Have you tested the coil, what gap can the spark jump?
I would say you better do a compression test, with all spark plugs out.
Do you need any further help?
I hope my advice has been of assistance to you.