03-04-2020, 02:52 PM | #1 |
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119508 Rail Pressure Sensor Plausibility: Pressure Too Low Before Engine Startup
i know it's the wrong forum, my motor is s63tu on f10 m5, but there are not many people active on m5post so i decide to ask for some advice here
So few days ago in the morning, i started my car but CEL poped up, "drivetrain malfunction" poped up on screen and engine died soon after rev tried to stablize around 800 during cold start. Then i scanned the code and got: 118011 Mixture control, Across bank mixture too Rich. (this one doesnt trigger CEL) 119508 Rail Pressure Sensor Plausibility: Pressure Too Low Before Engine Startup I flashed back to stock tune (was running bm3 stage 1), and tried to start again. The rev fluctuated around 800 again but car didnt die (along with kinda rough idle). After driving off, the car just ran fine. So today I kept eye on rail pressure and notice that rail pressure was very low (around 100 psi) before i started it up, and after I started engine, it rise to 1800 psi (is it normally that high????), along with rough idle as last time. note: all 8 injectors were replaced half a year ago due to leaky injector anyone has idea on this problem? |
03-04-2020, 03:48 PM | #2 |
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I've had a similar code when my HPFP was starting to fail to keep up with my tune. Even happened while idling for an hour, tried to drive off and the drivetrain message came up but was able to restart the car immediately after.
So check your HPFP of maybe the LPFP. |
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03-04-2020, 03:51 PM | #3 |
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well first thing, reset the adaptions. Make sure you dont have any weird leaks in the intake side of things or anything that could cause bad sensor values.. next id change the upstream 02 sesnors.
Thats what I would do. Im also wondering if you have a leak somewhere or a pump thats dying and rail pressure is dropping until it builds back up. Does it have trouble starting on the first try?
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03-04-2020, 07:45 PM | #4 | |
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03-04-2020, 07:49 PM | #5 | |
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03-04-2020, 07:55 PM | #6 |
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I'd say try the 02's first since that would be cheaper than HPFP. I'm not sure how to test the HPFP but systemically start from the least expensive points would be my suggestion.
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03-04-2020, 08:48 PM | #7 | ||
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03-04-2020, 09:06 PM | #8 | |
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http://www.bootmod3.net/log?id=5e5dae3dd10b4369882e10bf i have consulted bm3 support and they say afr seems way off but they can't tell which part is mechanically wrong Last edited by rickyf10; 03-04-2020 at 09:11 PM.. |
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03-04-2020, 09:22 PM | #9 | |
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03-04-2020, 11:28 PM | #10 | |
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I’m now installing o2 bypass and reset mixture adaptation later to see how it will be going |
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03-05-2020, 10:25 AM | #11 |
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do a full throttle log from 3rd gear to as high as you can go.
make sure traction control is off.
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03-05-2020, 10:50 AM | #12 | ||
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03-05-2020, 02:43 PM | #13 |
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Definitely gonna do a log but here in Vancouver is rainy... I’m gonna do it when sunny day comes
So here is a little update. 2 o2 bypasses are in place now. Startup this morning seems smooth but still a little fluctuations (within 770-830ish) when rev stablizes around 800. Before startup, I notice that my rail pressure is the same as one in low pressure system (88.4 psi). Is it normal?? |
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03-05-2020, 03:24 PM | #14 | |
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03-28-2020, 12:51 AM | #16 |
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so here is a little update on this. it turned out to be a faulty postcat o2 sensor.
the bank2 post cat o2 sensor sometimes loses voltage significantly (a little question on this: post cat o2 sensor is supposed to be monitor sensor but how come it affects air-fuel ratio ) my mechanic buddy swapped o2 sensors between bank1 and bank2 and the rich fuel mixture problem on bank2 is gone Thanks everyone here for giving advice! Last edited by rickyf10; 03-28-2020 at 01:32 AM.. |
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03-28-2020, 09:34 PM | #18 |
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