05-16-2023, 10:48 AM | #1 |
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N55 rough idle/misfire at warm startup
I know this isn't an F15 subforum but I think there's more activity here then the f15 side but it's the same engine.
Hey all, the symptoms are mildly rough idle/misfire when starting up from a warm engine for about 10 seconds. I can also feel it while cruising on a highway (this happens very rarely and when it does happen, its so mild that sometimes I cant tell if its the crappy NJ roads or the engine). I've been chasing this issue for a few weeks now. 2014 F15 N55 with 120,xxx miles. To add, I don't/can't remember having this issue before I had the car get its oil pan gasket and OFHG replaced. I've checked from what I can think/figure/find on youtube/tutorials the shop would've removed to make sure they didn't forget anything. What I have done/checked: -changed sparkplugs - NGK 97506 -changed coilpacks -Delphi -Checked ISTA and no faults/codes stored. -Did a smoke test after the air filter to rule out leaks, nothing. -ran misfire test plan on ISTA, nothing found. -Did a misfire counter, and the count is random and jumps between cylinders (again, this only within the first 10 seconds) Cyl1-1 count Cyl3- 6 counts And a minute or 2 later, I saw Cyl3- 1 count. -I checked the rail pressure comparing it to the set point value and its very close to each other. -Changed the spark plugs and air filter back in 11/2021 -reset adaptation -recalibrate the valvetronic, 450cycles I'm leaning towards fuel or air issue since the misfire jumps between cylinders. I am probably forgetting 1 or 2 other things I've checked. Any thoughts on what to check next? And, is there a misfire counter that doesn't reset on its own if it doesn't detect a misfire? It would be nice to get a misfire count on a long drive to see if the misfire happens in any other cylinders. Thanks in advance! EDIT 1: 3/26/24- Changed both vanos solenoids and the problem still exists. I'm going to check the injectors to see if they are leaking. Edit 2: 5/1/24- changed valve cover, no change (wasn't expecting) and no leak on any injectors. Replaced the MAF sensor and that fixed the weird cold start bogging for the first 3 minutes of my drive. The only issue I have right now is just the warm start issue. No issue while cruising.
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05-16-2023, 08:53 PM | #3 |
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Yup, I ruled it out since the misfire happens in random cylinders. I did put in an order for bosch coils so I'll swap them out just to rule it out for sure.
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05-17-2023, 11:48 AM | #4 |
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Some people have had luck using techron fuel system cleaner with similar very mild symptoms and initial rough idles. Use 1 bottle per tank and run 1-2 tanks in a row. https://www.amazon.com/gp/product/B0...e?ie=UTF8&th=1
BMW uses this same bottle rebranded |
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05-17-2023, 11:51 AM | #5 | |
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05-18-2023, 02:57 AM | #6 |
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It's Your coil pack. Mine is also an n55 f15. I also replaced the plugs it didn't fix it. Had to swap spark plugs to NGK 97506 as the bosch zr5tpp33 is no good and put in a fresh pack of Delphi coil pack. You won't get any codes regarding this, and swapping them from cylinder to cylinder won't change anything as your whole pack is weak. Your plugs will need to replace same time as well, and highly recommend not using the OE bosch. Only use NGK or OEM BMW Bosch.
Also, don't just start doing adaptions and calibrations. Those are only meant to do when replacing and installing new parts for those certain items. It is not good for wear as it resets calibration on them as it has zero wear/new part. Here is more information regarding the trash bosch plugs. https://f15.bimmerpost.com/forums/sh....php?t=2014403
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05-18-2023, 04:48 PM | #7 | |
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And looks like I'm running Bosch ZR5TPP33. I'll order a set of NGK 97506 and swap them later. The Bosch coil packs should be delivered tomorrow. Thanks!
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05-18-2023, 08:57 PM | #8 | |
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05-18-2023, 09:09 PM | #9 | |
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05-18-2023, 09:30 PM | #10 | |
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Quote:
https://www.bimmerfest.com/threads/c.../post-13410647 Thread #19.
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Last edited by F15_SGM; 05-18-2023 at 10:35 PM.. |
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05-18-2023, 10:53 PM | #11 | |
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05-19-2023, 08:41 AM | #12 |
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Which Delphi coils are you running? I'm seeing 2 or 3 model numbers.
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05-19-2023, 01:38 PM | #14 |
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Order is in!
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05-20-2023, 10:02 PM | #15 |
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Changed all 6 coils with Delphi and didn't fix the issue.
Edit: I'm going to order a set of NGK 97506 spark plugs and see if theres any difference.
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05-21-2023, 02:30 AM | #16 |
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Yes, do both at same time. Also i wouldn't put the new coils on with bad plugs just incase it shorts the new coil. Hopefully the new plugs will resolve everything.
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05-21-2023, 02:10 PM | #17 |
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Swapped the plugs, no change.
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05-21-2023, 05:13 PM | #19 |
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Yup. It could also be bc during cold start, the rpm’s are much higher.
Outside of the starting up at warm, can drives perfectly. WOT no issues. |
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05-21-2023, 07:43 PM | #21 | |
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After thinking what else to check, I decided to check the TMAP sensor. I'm certain it's not the MAF because unplugging it makes no difference. Ran a test plan that shows the reading of ambient, charge pipe and intake mani pressure. It ISTA it says +-25 deviation is fine but I'm getting -50's while the engine is idling. Also, the "setpoint value for the intake pipe vacuum" was blank.
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05-21-2023, 11:34 PM | #22 |
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Okay, I think next step would be to investigate the injectors. Try techron if no change it's another issue. Can you describe what you feel when driving more in depth? Have you checked for any vacuum leaks?
Crankcase Ventilation hose is very common to be broken and many other brittle plastic hoses. Last edited by F15_SGM; 05-22-2023 at 06:08 AM.. |
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