08-14-2022, 07:17 PM | #1 |
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Help on Spark Plug Replacement M235i
Hi All,
I proactively replaced the first 4 spark plugs on my BMW M235i. Didn't have any misfires before but after replacing the first 4 it's not throwing errors but definitely feels like it's misfiring. I've rechecked the connectors, they're connected solidly. I can recheck torque, but would that cause misfiring? If I let it run will it eventually tell me which plug is faulting? I'm wondering if I should backtrack and put the original plugs back in but it's been a hell of an elbow workout just getting those in. Any advice would be appreciated. |
08-15-2022, 07:19 AM | #2 |
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if they're too loose, you'd have compression loss and yes that would result in misfire.
where'd you get the spark plugs? counterfeit plugs are out there on ebay and similar sites.. finally, the first 4 spark plugs should be minimal effort.. you simply take off the engine cover and the ignition coils and plugs are right there... so what do you mean by elbow workout?
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08-15-2022, 12:52 PM | #4 |
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Why did you only replace 4?
If you have 4 new plugs and 2 bad plugs, that variation in plug consistency and health can and will surface issues. I'd double check your work on the first 4 and then go back and do the last 2. they arent that hard to reach. Remove the cowl with 6 bolts, the struct brace with 4 bolts and then pull off the insolation and you have all the room in the world. |
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08-15-2022, 01:34 PM | #5 |
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Ok, so I backtracked and put the original plugs back in, still misfiring so I'm clearly installing something incorrectly as the originals were not misfiring initially. I was using an in/lbs torque wrench that only went to 200 in/lbs. Everywhere I'm reading it needs to be torqued to 23 nm so that would be (203 in/lbs) so I'm going to get a ft/lb wrench and torque them to spec since my current one doesn't quite get to that spec.
The other thing I'm wondering, so connectors look good and lock into place but when you push them down into place are you supposed to hear a click or anything? I push them down into the notches they're supposed to go into, but I don't know if they're supposed get pushed further down or something. |
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08-15-2022, 01:36 PM | #6 |
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08-15-2022, 04:08 PM | #7 | |
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When you plug the harness in, yes it should click once fully seated. Then you lock down the latch, which also makes an audible 'click when latched down fully. Did you gap the spark plugs? What kind of spark plugs are you using? Have you pulled the CEL to see what codes/cyl is misfiring as opposed to just blindly shooting in the dark? |
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08-15-2022, 07:23 PM | #8 | |
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They're pre-gapped so haven't messed with gapping, which could be a cause? I haven't gotten any misfire CEL codes yet, although I haven't left the car on super long but yes, I agree if it throws a code it would make this a hell of a lot easier. Maybe if I let it run awhile it'll throw a code for me. |
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08-17-2022, 03:34 PM | #9 |
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So knowing that you are at 56k miles, and this is probably the first time the plugs have been changed. You absolutely need to change all 6 at one time. Not doing so will only hurt your engine over time.
Yes, if it is occasionally misfiring it will take the engine running for a few minutes to set the CEL; unless it happens on start-up.. Give it a little gas while (maybe take it up to 2K - 3k rpms) and see how the revs climb, do you notice any hesitation? If so, at what point? How is the throttle response? |
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08-17-2022, 09:12 PM | #10 | |
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08-18-2022, 10:21 AM | #11 | |
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Quick question, when you pulled the old plugs out how did they look? Can you post pics of them? |
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08-18-2022, 05:37 PM | #12 | |
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08-18-2022, 06:25 PM | #13 | |
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