Just had a set of LG longtube headers, new set of MSD wires and NGK TR55 plugs installed on my 2000 C5. The shop that installed the headers diagnosed a misfire and reported the caused as two faulty coils. Seeing as I still had 100miles before my extended GMPP warranty expired I took the car in for the misfire and a few other issues. The dealership diagnosed the misfire being my newly installed (2 day old) wires and plugs because they were not GM parts. Reluctantly I told them to replace the wires and plugs until I found out it was going to cost me $900 parts and labor plus $190 for diagnosing the problem. I told them to forget it and I would instal the GM original plugs and wires myself and save the $900.
Well I picked the car up yesterday and drove it home (misfire still present). Later that night I went to get gas and the car barely started. After getting gas the car would not start at all. Today I replaced the battery with a Optima red top but when I tried to remove the positive cable the terminal broke off. Sure enough my battery had been leaking. Now with the new battery inplace my misfire is gone.

Is it possible that a bad battery would cause a misfire?
Now that the problem is corrected without redoing a tune up(plugs and wires) that GM said was required, can I get the $190 diagnosis charge refunded? Should they have not reported the faulty battery to me (they must have had to jump start the car when I picked it up and they disconnected the battery to replace the tranny and AC control unit)? The car is about 20miles over the warranty, will GM pay for a replacement battery and clean up the corroded frame under the battery and replace any other damaged components?

PS I have never had any luck dealing with dealerships, they never want to assume any responsibility.

 

Well, maybe I am shooting in the dark on this one, but my understanding is that until the alternator is cranking out juice, the ignition system is running off of the battery. So I would think a dying battery could certainly induce a misfire because of low current being provided to the coils. But I don't know the threshhold on when the alternator actually kicks in. The battery is running the starter, of course, but at what point does the alternator actually take over?

 

well it's possible for it to happen but my guess would have been a broken or mis-gapped plug .. but if the problem was a leaking AC Delco battery you might want to contact somebody soon, if im not mistaken there was a recall or something to that effect on the leaking batteries.

 

No way guys, the battery won't cause it. Look at the plugs, wires, or a coil pack.

 

no way once the car starts the alt takes over

 

Yes it can cause misfire since the PCM is critical of voltage level, its part of the limp mode. If the voltage is low when the engine is started the PCM commands more voltage to the injectors pulse width to allow car being driven somewhere safe so now engine runs richer which also can cause misfires

 

Would GM replace the leaking battery even though it is 5yrs old?