Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

1999 Pontiac Grand Am GT Misfire

I have a constant misfire on cylinder 5 with an A circuit code to go with it. You can ask me for more details but I would like some advice on steps to diagnosing or fixing. If somebody on here has had this exact same issue please help me out.

Post your codes. P0305 etc.

1 Like

If you want advice, I suggest you tell us EVERY detail of your error codes - the code numbers, please - and what you are experiencing. We don’t want to play “20 Questions” with you. It wastes your time and ours.

1 Like

Misfires are usually diagnosed by swapping components between cylinders and seeing if the misfire moves to the other cylinder or not. Spark plugs, coil packs, injectors, etc. Sometimes a compression test is required.

Likely a bad fuel injector. OR bad wiring to the injector. A resistance check of the injector is warranted. Compare the resistances of #1, #3 and #5. If #5 is different, replace it. If it isn’t, you have a wiring problem. Check the connector and the harness for damage. Best way is pull the ECU, find the wire for #5 and check the pin-to-pin resistance.

If you fix the P0205, it should fix both codes.

Still pretty stingy on details about your car and the problem, I notice.

the problem may very well be the injector OR the wiring, as already suggested

If you want to be sure, hook up a noid lite in place of the injector and let the engine idle

If the wiring is okay, the noid lite should be blinking, in which case you know the injector needs to be replaced

1 Like