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Nissan Maxima Ignition Coils going bad?

I haven't had a check-engine light yet, but at idle, my 1996 Maxima has a sporadic misfire -- there's no rhythm to it at all. Does this sound like a symptom of a coil going bad?



What would be a good way to test them without having to replace all 6 of them for between $35 and $50 each?



The car has about 175,000 miles on it. I just put in a new set of NGK iridium plugs, and hope I didn't damage any wiring in the process (that doesn't seem likely, but I guess I can't eliminate that possibility).
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Comments

  • edited April 2011

    Could be a spark-plug also...Or a clogged injector.
  • edited April 2011
    If it is a mis-fire, there may be a PENDING code to help narrow this down. Getting the codes scanned should show any pending codes.

    If your using 87 octane fuel, this could also be the problem. You'll have issues using low-octane fuel in a 'premium required' car.
  • edited April 2011
    Weak spark usually rears its ugly head under acceleration, more voltage is needed with higher cylinder pressure.

    It could be dirty fuel injectors; pour a bottle of Chevron Techron in the gas tank.
    It could be a small vacuum leak.
    Does this car have ignition wires? You could have damaged an old, frail wire when you changed the plugs. Should be changed anyway if they're 15 years old.
    Next step after all that would be a compression test.
  • edited April 2011
    Yep, it sounds like an ignition coil. I've got a 97 Maxima with 157k on it, and I've already had to replace 2 of them. It will eventually turn on the SES light. You can have the code read at that time, and it will tell you which one of the ignition coils is bad. Many times the coil for cyl #1 is the first one to go bad.
  • edited April 2011
    It's getting worse, but still no CEL.

    I notice that when I let it idle in neutral, it does not misfire. When the idle settles down maybe 100 rpm from the time I stop (leaving it in Drive), it then starts missing, and it's not rhythmic.

    I will check for a pending code, though.

    I'm wondering if an Engine Coolant Temp Sensor may also cause this. I had another symptom over the winter -- hard starting when cold -- that usually indicates an ECTS. Does that even make sense?

    And I have been using 87 octane Chevron. Switched from 91 a few months ago.

    At least the #1 cylinder is easy to get to. That's a 10 minute job -- five if I find the tools right away.
  • edited April 2011
    I accidentally put some 87 octane in my Toyota Supra once. The tank was near empty, so there wasn't much 91 octane to mix with it. I'll never do that again. The car idled weird, and had mis-fires when accelerating from a stop. I managed to siphon about half of the fuel out and replace it with 91 octane. It took running out that tank and replacing with 91 octane to get it running good again.
  • edited April 2011
    Hooked up my code scanner yesterday, and there are no pending codes.

    The mileage seems to be down slightly, but it's hard to tell. I normally expect to go 320 miles on 16 gallons, and it needs a refill now at 300 miles. If it went from 20 to 19, I just can't say the mileage is suffering -- too small a sample size, and 20 to 19 doesn't really represent anything.

    I'm at a loss. I haven't run the manual's test (just an ohm-meter) yet, but that's next.

    If I do decide to replace the coils, I've found out that the local store wants $135 for each coil, the dealer wants $100 each, and that I can get them on rockauto for $35-$50 each, or I have my pick of sets from eBay for under $200 (some way under $200). If it's only $200, I'm not going to stress -- this really is a 30 minute job to change all 6, and it's hardly like buying a house. But I'd like to know the experience people have had with this variety of options. If the $170 option at eBay has been working for people -- why not try it?
  • edited April 2011
    It would be cheaper to try a tank of premium first. I really think that is your problem. If it was the coils, the CEL would definitely be on. Mis-fire detection is one of the ECU's functions.
  • edited April 2011
    Well, my fuel light is about to go on, so I guess it's worth a $3.20 investment to see if that helps. Thanks, I'll try that first.
  • edited April 2011
    Put a tank of premium in it--no change (but I've only driven it 3 miles, so I'm not sure it would improve yet).

    Checked the coils -- at all about 300-400 ohms resistance, which should be acceptable (zero ohms is "no good").

    Injectors? Or could it be possible one of the plugs is weak (even though it is brand new)?

    How does one test injectors without lighting oneself on fire?
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