im having a dead miss in my 3,4 cylinders Ive done almost everything i can to fix it that i am aware of. Ive replaced my spark plugs,wires,coils, replaced every gasket in the upper part of the head, replaced what the coils even sit in. even replaced my rollers. im stumped and my mechanic is stumped. any suggestions or ideas?

oe and the engine is a 3800 series II forgot to mention that

How do you know there is a miss? Are you just down 2 cylinders?

What are you missing? Fuel? Spark? Compression?

i have spark and fuel im not sure about compression. we havent run a compression test on it. but we have replaced the headgastets and up basicly

the computer says i have a miss in those cylinders

you see if you have power and ground signal at those injectors? move them to different cyl?

three elements that any engine requires to run. Fuel, Spark, and Compression. Very first thing I would do in your case is figure which one you don't have and proceed then to figure out why you don't have it. If you have fuel, and you have spark- then I would say check compression. Check compression and compare with all cylinders. Once you have verified that you have low compression you can next perform a cylinder leak down test- this will tell you what is causing the compression loss. Hiss in the exhaust = exhaust valve leak. Hiss in intake = Intake valve leaking. Hiss in crank case is likely to reveal that there is a problem with rings. lastly if you have pressure in your cooling system then you may have a head gasket problem or a cracked/ small fracture in the head. If there is no compression issues then you could have other issues that can cause compression to be off. It could be a camshaft that has worn lobes- that is also a possibility. hope you figure it out! good luck to you!