LeBaron

Silver blazer, I don’t know how to check that. How can I find out if it’s switched to closed loop or not?

Superdave160, I thought so too. However I replaced the intake gaskets when I replaced the injectors. I have also sprayed around the intake while the engine was running. I don’t think a Vacuum leak is not the problem. Any other suggestions?

Got it. Thanks for clarifying. That's what we are doing so far, hoping it becomes worse so we can find the source of the problem. Thanks.

Replying to KARNUT. What are you talking about?

I replaced all 8. I guess I need to pull the intake. I don’t know what else to do. Maybe it is carbon build up. I’m puzzled as to why it only misses at idle. Thank you for taking the time to help.

newdude, I pulled off the valve cover and there is no excessive play in the rockers. People keep saying it's mechanical. If there were a bent push rod, worn cam lobe, or bad lifter, there would be noise or the rocker would be off the pushrod. Also it would miss all the time. I only have a miss at low idle. I have confirmed this with a scanner. Also #3 is not one of the cylinders that drop out, so it should have regular lifters. I know there is a problem with the lifters that drop out (DOD) but #3 cylinder isn't one of those lifters. And if it were, I would hear obvious tapping and the miss would be all the time. Can anyone tell me if GM uses 8 regular lifters and 8 dod lifters, or do they use 16 dod lifters?

Cold, no miss. Yes, I have verified the miss goes away above idle with a scanner. I have also cranked the engine over with the valve cover off and there is no excessive play in the rockers while cranking, therefore, a cam of lifter problem is not likely.

I replaced the injectors. I did not look inside the intake for carbon. I got 190 psi in 4 revolutions. Yes I swapped plugs, wires, and coils one at a time. I also just changed the plugs but didn’t help. I also made sure the butterfly was clean in the throttle body. It idles really low. About 550 and less. The miss goes away above around 750rpm. Maybe it is a valve not seating at idle. I just don’t see why it doesn’t miss out above idle.

P0303. #3 Cylinder missfire.

Yes, the intake has been off. Everything pointed to injectors so I changed all 8 injectors. Had to take off the intake to replace the injectors. I installed new rubber gaskets. Still has the dead miss at idle.

Plug, wire, and coil is good. 190psi compression. Replaced all fuel injectors. Rockers moving normal visually during cranking with valve cover off. #3 cylinder is not one of the cylinders that drop out during DOD. 192k miles. Runs great off idle. OBD II shows no missfire above idle driving down the road but as soon as you come to a stop, #3 cylinder has a dead miss. Any ideas?