Some one please help! po303 cylinder #3 misfire!! I went under the hood changed my plugs, swapped my wires, new distributor cap, rotor, and finally ran seafoam through the fuel system to try and fix this problem, None worked So i swapped my 1/3 injectors to see if the codes jumped at all, nothing has worked! Can anyone tell me what my next step should be!? i am complete lost! The truck smells alittle rich but i think that is just a small timing issue. the truck isnt smoking or anything so i dont believe its a gasket issue. 5.9l R/T 3/4cam cool air and full exhaust. someone please adivise the weekend warriors who may end up on foot,lol

 

Sounds like it is a wiring issue. Since changing injectors didn't do nothing that means it is the circuit. Check for positive at the wire. Then check to see if the negative wire has continuity all the way to the computer terminal. Check the stickies at the top of this section for the service manual. It has wiring diagrams that will help you.

 

The problem maybe a bad seat in the cylinder head. This has been a common problem with the 3.9L,5.2L and 5.9L engines. Do you have more than 70k on the truck? Any mileage above 70k is when the cylinder heads start to fail. You need to do a dry compression test and record and then a running compression test and post your findings. Running compression is with just the spark plug out and hook up a gauge and start the engine, Reading should be 1/2 of the dry compession test. If its lower, then you have a either burnt valve or a crack seat.

 

I thought the truck would be blowing smoke if i had a crack, or bad gasket, and yes i have like 145K I bought it about a month ago from a guy with no mechanical knowledge or care, so he didnt know and didnt care to let me know of anything going on... what about an intake gasket could the be a cause?

 

Hey crazy i took your advise and tested my injectors, They were good... unfortunately b/c now i have no idea... I ran a compression test on all 8 hard as h*ll to reach cylinders lol, they all showed up around 110psi. i checked my rockers and push rods today also checked out decent, except i noticed on #3 one rocker had came loose cause it to not drop about 1/8", i tightened it and erased the codes i've put 25 miles on it since then, no codes..... if they come back up do you have suggestions what so ever.... i'm trying like hell not to bring it to the local 100/hr "friendly specialist". any help would be greatly appreciated.