New Misfire [Archive] - Forum


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11-03-2009, 05:01 PM
ok so my car is hating me again. i scanned it and im getting a misfire in cylinder 5, and i am also leaking oil (don't know if they are related) and i also leak a lil coolant but thats due to a loose heater core line. i just put MSD coils and wires. and i just put Bosh Platinum 4 plugs. after all of that its still missing and i dont really know what to do other then check the injector on that cylinder.

Any Ideas?

11-03-2009, 09:39 PM
ok plugs look all the same, did a compression test, it ranged from 175 psi to 185 psi, and all in between. cant do a leak down test yet need to get a different plugin for my air compressor and i should be able to do that tomorrow.

11-03-2009, 09:44 PM
You shouldn't have to perform a leakdown test. If your compression is good then its doubtful that a mechanical problem is to fault. Especially if the PCM can narrow it down to 1 cylinder.


Use only AC Delco or NGK plugs. Autolite will work in a pinch. Single electrode, platinum or Iridium makes no difference.

I've actually fixed misfire problems by replacing Bosch plugs with factory AC Delco parts.

If switching back to stock plugs doesn't fix your misfire, switch coils and see if the misfire follows it. If the miss doesn't follow your swapped coils, its likely related to the fuel injectors.

11-03-2009, 11:09 PM
well i had the HO coil packs msd wires and single platinum bosch plugs. i had to replace one of the HO coil packs before and that and it fixed the misfire. (cylinder 5). then a month later it started missing again so i said F it and bought MSD coil's new MSD wires and the bosch platinum 4 plugs. and still missing...

11-04-2009, 02:41 PM
100% agreed with Malaclypse, get that BOSCH out of there, i known many many people use BOSCH and all it did was cause them nothing but headaches with missfire codes, they bring it to me and thats ALWAYS the first thing i check and,i'd say 98% of the time that was the problem,they'd use BOSCH cause it was cheaper and cost them more in the long run

11-04-2009, 04:45 PM
Start with the plugs.

And what do you mean by "HO" coils? High output, yes.. but what brand? OEM is fine even for modded cars.

The MSD coils served me well but I think they failed after I sold the car. Maybe 60k miles on them?

11-04-2009, 07:11 PM
I know you've spent a lot on that but I would replace the lot with Delco parts. The coils, wires and plugs. Ive seen GP's put down over 500 to the wheels and still use "factory" wires and coils! Cartuning Performance here does the turbo conversions to Grand Prix's and he recommends nothing but AC Delco! He's doubling the output of those motors and swears by Delco.

11-06-2009, 04:32 PM
ok misfire is fixed. put in ac delco rapid fire's. fixed my coolant leak but now it turns out for some reason the metal coolant line that comes from the thermostat housing to the back of the engine bay wasent bolted down and it blew out, it was leaking were the metal and rubber line met. now im guessen it blew cause there was finally enough pressure in the line.