2000 Malibu - Misfire

[Fishinguy40]

A few weeks ago my daughter complained that her car, a 2000 Malibu, would run rough in the morning when it was cold and that the engine light came on. The car would run fine after warming up. My first thought was maybe the EGR valve. When I finally got the chance to check the computer last weekend, engine light was out and there were no codes stored in the computer.

Tonight she called 5 minutes after leaving the house (car was cold again after sitting all day Friday and today) and said the car was running rough and that the engine light was flashing. A misfire, since the engine light was flashing. She called about ten minutes later and said the car was running fine but the engine light was on steady. An hour after that she called and said one of her friends checked the computer and got a single code, misfire on cylinder 3. There were no other codes.

Well at least I know what cylinder. But any ideas what would cause a misfire only when the engine is cold but then stop after it warms up? Maybe a sticky injector? I plan to look at it tomorrow but there are no guarantees that it will repeat, since it has been somewhat random. I hate to try and move parts around from one cylinder to another, watching to see if the problem moves with it. I also hate to just replace parts hoping that I get lucky. Any logical ideas?

Appreciate any suggestions.

[Macgyver55]

What engine, 3.1?

Could also be a coil pack, plug wire or spark plug. They sometimes show up first on cool & damp mornings, and get better as the motor warms up and drys out.

[BoxMN]

I am no mech. but my 1998 was running rough and eng. light lit and it ended up being fuel pressure regulator. Fairly easy fix even for me and it is common problem. Good luck.

[Fishinguy40]

Fuel pressure regulator would probably cause random misfires not just a single cylinder. I have seen this issue on both the Malibu and my daughter-in-laws Impala.

I will probably break down and swap injector with another cylinder, swap spark plug to another, plug wire to yet another and wait to see which cylinder the problem moves to. It's the only way I can think to diagnose the problem without having all the necessary tools available.

[Macgyver55]

I will probably break down and swap injector with another cylinder, swap spark plug to another, plug wire to yet another and wait to see which cylinder the problem moves to.

I'd start with the coil pack, wire and plug first. Those will be your easiest swaps.

[Jeremy airjer W]

I would start by checking for worn out plugs. I have had a couple this week with the same symptom. Both times the plugs where well over .080". A new set of plugs on both and one got a new set of wires and everything was good (That one had a misfire in history for number five but the #1 wire was leaking when wet, go figure).

[Fishinguy40]

Macgyver, good call. I started to tear into things and found the #3 coil post corroded up and pitted. Pulled the whole coil pack so I could clean all of them real good. Ended up putting new plugs and wires in because I broke two wires trying to get them off the spark plugs. Put some dielectric grease on everything and shes running good, so far.