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05-25-2016, 07:50 PM | #1 |
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Possible HPFP issue please help
Hey everyone
I need some help in my having a weird issue with my 2008 n54 135i so when I bought the car it had a very slight idle stumble but started right up. The previous owner had the injectors and spark plugs swapped about 8 months ago. I changed 9ver to 5992 ngks correctly gapped and it made the cold start idle worse but here is the thing. It did fix the misfire under load situation . Now the only time it misfires is cold start and when in neutral when free reving below 3k rpm it's very isolated I've tried coil packs to no avail. The last thing I can think of is HPFP I have only gotten limp mode once and never again so I'm just looking for guidance thanks in advance |
05-25-2016, 08:17 PM | #3 |
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BMW plugs. Walnut blast valves.
Is the car modified?
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05-25-2016, 08:40 PM | #5 |
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Then you need to log the problem.
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05-26-2016, 10:58 AM | #8 |
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I have had the same issue since swapping to NGK 5992 plugs, as well. Gapped to .019 per Ken at Wedge. I too thought it might be the HPFP, but logs looked good at idle and under WOT. It was in the dealership for new turbos this past week and I explained the rough idle on a cold start and requested the tech to check the HPFP. He said the pump is working fine, but it could be the check valve in the Stg 2 LPFP. After shut off, the check valve bleeds off and upon starting it again, there isn’t enough pressure and car run rough and misfire. He said try turning the ignition on before firing it up, give it a second then press the brake and turn the car on. If it elevates the rough idle, it's the check valve in the pump. Unfortunately, this didn’t work with mine; my LPFP is about 5 months old. I'm not wondering if it's the plugs, but no misfires through any other area or WOT. Fuel looks good in logs, so don't believe it's an injector, but I'll probably check those next. Just did a valve cleaning abut 4-5k miles ago. Hope this helps.
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