Misfire with no code

[GPFred]

Hi all. Been here before with various problems. I have a 2000 GP 3.1 with about 94k on it. Over the last year I have had a new cat installed, 2 coil packs, wires, plugs, intake mainfold gaskets, three bank 1 O2 sensors, and just this weekend did the fuel injector gaskets. The upper gaskets were done by the dealer when they did the intake manifold gaskets but did not do the lower ones. Anyway, dealer told me the lower fuel injector gaskets were leaking air, so I replaced the gaskets this weekend. Well, before the gasket change I was getting a code for the bank 1 O2 sensor for insufficient voltage. This the dealer claimed was caused by the leaking gaskets. I had my doubts, but did the gaskets. Now I am not getting any codes, the car runs better. BUT, still seems to lack power on heavy acceleration at speed. There is a slight miss that can be felt at idle and there is a put-put sound at the exhaust. When you let off the brake, there is a jerking in time with the miss. Miss goes away on acceleration. Miss is not noticed when driving. I am currently running a bottle of Redline fuel injector cleaner in the gas. Any suggestions on the miss?

[richtazz]

Possibly a Mass Air Flow sensor going bad or dirty. You can try to clean the elements with Electric parts cleaner, just be careful.

[jimmyv-21]

i agree with rich that it could be a maf- also check your fuel pressure/ injectors. dirty injectors- which you have close to 100k so that could be your problem- will cause the same symptoms. last but not least, if you put on bosch plugs or wires, you will need to do them again and go back with stock ac-delcos. the stocks are much better than the bosch's, and many have had the same prob simply because of putting bosch plugs on.

[GPFred]

I'm using champion plugs, never had a problem with them. The wires and plugs are new from back last spring, haven't had a misfire problem with them since intalled. I will look into the MAF possibility and may replace the wires as we were moving the packs and wires around when I did the injector gaskets. I'm running a cleaner thru the system now.

[GPFred]

Ok, got some more info. I got a code this afternoon for a misfire on the number one cylinder, P0301 code. Even with this miss the car seems to run better but still bogs down on heavy acceleration when at speed. What's interesting is I didn't have a misfire before I changed out the seals on the injectors. Sooooo, my question is could it be the injector has gone bad, or something else. The plugs and wires were new last spring and not causing problems before the seal job. I will check the MAF sensor as well. Could a bad fuel pressure regulator or throttle position sensor causing the bogging down? I'm going to see about renting a fuel pressure gauge to check the fuel pressure from the pump to verify its not fuel pressure related. But this miss is bothering me. Thanks for the help.

[richtazz]

The bogging is due to the mis-fire code. If the misfire is bad enough, you're basically running on 5 cylinders, which will cause bogging under load. You can try switching a plug wire from cylinder 1 to another cylinder. If the miss moves to that cylinder, where you moved the wire originally on cyl 1, you have a bad plug wire. If the miss stays on 1, it's most likely a bad or clogged injector on cylinder 1.