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2009 3.7 ongoing misfire trouble

4K views 5 replies 4 participants last post by  rblapham 
#1 ·
I have a 3.7l with misfires on cylinder 1 - 170,000 miles. This is the one engine with 3 coil on plug coils with leads from the three coils to the other bank of plugs.

This portion may or may not be relevant but back when it had about 50,000 I would get a sporadic DTC light while driving which the dealer eventually fixed by replacing a coil. I wish I had more info on which one it was but they replaced the bad coil, changed out the plugs and cables and no more problems here.

Fast forward to 120,000 miles and some water got on top of the engine during a wash (don't ask - my better half took it to get detailed) and it blew up coil 1. At this point the boot on the coil wasn't even really sealing and no amount of dielectric was goint to keep it from misfiring. Took all the coils out and ended up replacing all of them because I wasn't thrilled with the amount of corrosion on the contact to the plug. I was able to get a deal on some OEM coils at the time and just said might as well swap them all and keep 3 and 5 as emergency backups. I also replaced the plugs/cables when I changed the coils.

Fast forward again to 150,000 miles.Car starts to misfire on damp days or days after heavy rain. I don't think much of it because the MIL hasn't come on yet and it only seems to stutter a bit while idling (or reverse) on really random days. It also doesn't misfire if the car is running in the rain, only on startup. So I'm starting to think maybe I'm just crazy. The problem continues to progress until I end up with a misfire on coil 1 - again, only sporadically after rain and when in reverse while the car is cold. This progresses to the point where the car misfires consistently after damp weather on cold starts and now after a cold start it seems to misfire somewhere between 1200-1500 RPM. It's like it would gets stuck there misfiring but if I let off the gas and hit it again it would stop. Or if I was chugging along at 2,500-3,000 RPM no misfire.

Finally it got to the point where it was misfiring consistently enough it needed to get swapped out again. I was able to catch the coil arcing to the head at night. Replaced it (and the plugs again) and no more misfiring. I also found that the ground strap to the plenum had corroded through so I bolted the end back to the stud.

Fast forward to 170,000 miles. It's doing the same thing it was at 150,000. I've probably spent more money than any smart man would on replacing coils at this point. I'm thinking - maybe moisture is getting onto the engine and pooling in the plugs holes (coil 1 is the most exposed). But I can't for the life of me tell how the moisture is getting in and in an amount that would seep under a coil boot. I do notice that the heat shield on the hood is wet after rain though, and it seems the dampest right over coil 1 but there's no visible dripping. I pulled the heat shield and poured buckets of water over the hood and nothing. It's not damp. But why would the shield be wet after a rain? I'm really scratching my head on this one and I'm considering RTVing the windshield washer nozzles as a last resort.

Am I chasing a goose looking for water infiltration? Should I just stand out there with a hose and hit the thing until I get moisture in the shroud to try and figure out where it's coming from? It just seems insane because I've put more water over it than it should be seeing during a rain. I've replaced the gasket at the front and back of hood thinking maybe that's it. But maybe it's not the water at all. I've heard people say you should be able to drive without a hood and I've heard other people with Ford hood scoops that swear they cause premature coil failure. When it's misfiring I do see (and you can even hear the speakers pop) the misfire to the head so I don't think it's a problem with the injectors.

Could it be something with the PCM causing early failure of the coils? I have yet to run a compression/leakdown test either but would that cause a coil to fail prematurely?

I have also noticed that for the life of me I can't get the ECO indicator on. I reset it from display to don't display and back to display and nothing. And I'm not talking about when I have a MIL on. I don't remember exactly when that started but I haven't been able to get it on since as early as 120,000 miles. I don't even remember what it looks like - is it text in the EVIC or is an actual light that could have burned out? Again - probably unrelated and functionally I don't care but it's odd.

If I didn't have a lifetime powertrain and wasn't emotionally attached I'd just get rid of the thing at this point.
 
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#6 ·
@spisi
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