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Old 12-04-2012, 03:03 PM   #1
BennK
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The check engine light that won't die

So i have a CEL that came on and kicked back a code that says the 4th cylinder misfired on start up. I replaced the spark plug and i replaced the wires. I was told if it was a bad coil pack that it would read a constant misfire. I"m at a loss with what to do now and i would hate to bring it to the shop for an easy fix. Any ideas?




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Old 12-04-2012, 03:06 PM   #2
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Don't mean to ask a stupid question, but you said you replaced the wires (spark plug wires?) yet you've been told that the code means you have a bad coilpack. Does this engine have a distributor & wires or a coil-on-plug ignition?
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Old 12-04-2012, 03:10 PM   #3
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Are you experiencing a problem after replacing the hardware?

If not, you need to unplug the battery for several minutes and hook it back up. That should clear your code and CEL if its all been fixed.
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Old 12-04-2012, 03:11 PM   #4
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Yes i replaced the spark plug wires. the guy i talked too had told me that if the coil pack was bad it would misfire during operation and not just on start up. Oh and dont worry if you feel like your asking me a dumb question becouse i feel like the ones i ask are prolly a bit mechanically retarded myself. Any help or questions that would assist me go ahead and fire away. thanks for taking the time to help!
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Old 12-04-2012, 03:16 PM   #5
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Ok, if your car does indeed have spark plug wires, tell that 'guy' that you don't have coilpacks.

Next question..does your engine have a mechanical distributor (round), or a module (square or rectangular) ?

Another source of a misfire could be from a bad connection at the fuel injector for that cylinder, or a malfunctioning / leaking injector.

I once had an Oldsmobile that stumbled & occasionally backfired on startup because one of the fuel injectors leaked into the intake manifold when the car was shut off.
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Old 12-04-2012, 03:31 PM   #6
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it looks to be a square module then. :)
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Old 12-04-2012, 03:42 PM   #7
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If there's the slightest flaw in the module circuitry, or the heat has compromised it and that cylinder isnt' getting consistant spark, there's your misfire.

If it's not the module, it's gotta be the injector, and unfortunately, unless someone's able to do a definite diagnosis, your chances are 50-50 for either having an issue.
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Old 12-04-2012, 04:24 PM   #8
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Thanks cbdallas and the rest of ya, hopefully i can get this squared away!!
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Old 12-06-2012, 12:24 AM   #9
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I don't know where some of these others come from but when I see a set of 4 coils on a single unit I call that a coilpack.

Pull the coil and look at it carefully on the outer case in bright light. These commonly crack small cracks that can be just about anywhere on the coil case plastic. It is VERY common to misfire only in little bits on these, I've lost 4 now to it and not a one misfired 100% of the time, only very slight cutouts under load, they idled and low load/rpm beautifully. The cracks let moisture in to corrode wires, the miss will be very light at first. I never registered a single DTC during all fails. Look VERY close at the wiring going right into module too, common for wires to crack there at insulation to make same problem, they were too cheap and the wireloom there is too short, MAF sensor pulls loom the other way to crack wires at coil connector. You can buy the connector, I rebuilt one for mine for maybe $2.
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