hesitation, rough idle and long random cranks.

gutlesswagon

New Member
Jun 14, 2022
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i recently picked up an 08 535xi and immediately threw a code for hpfp and low fuel pressure sensor. replaced both and got out of limp mode and had full power again. now it is giving me random long cranks and a definitive rough idle. wont throw any misfire codes but i can feel it in the seat and also it hesitates sometimes. i got an mhd wifi adapter that just came in the mail today and did my first datalog. alomg with weird spikinmg fuel trims i also noticed that im getting cylinder timing corrections? i have absolutely no clue on what to look for with this thing or where to start so i figure ill post the datazap and see what you guys think also had a couple of shadow codes which may be related! thanks in advance!

 

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wheela

Sergeant
Jun 4, 2021
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Twin Cities, MN
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2015 e84 X1 35i Msport
I haven't had the problem myself, but i've seen a lot of threads where people with these symptoms ended up replacing their low pressure fuel pressure regulator. Maybe you could collect a log from cold start (or whatever scenario you get the long crank), and monitor low pressure fuel pressure to see how it looks? Start the log before you start the car, so you can see the fuel pressure before you start. I'm n55 (no low fuel pressure sensor), so i'm not super familiar with what the fuel pressure level should be before it causes problems, but i'm sure others here know and would be willing to chime in.
 

gutlesswagon

New Member
Jun 14, 2022
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I haven't had the problem myself, but i've seen a lot of threads where people with these symptoms ended up replacing their low pressure fuel pressure regulator. Maybe you could collect a log from cold start (or whatever scenario you get the long crank), and monitor low pressure fuel pressure to see how it looks? Start the log before you start the car, so you can see the fuel pressure before you start. I'm n55 (no low fuel pressure sensor), so i'm not super familiar with what the fuel pressure level should be before it causes problems, but i'm sure others here know and would be willing to chime in.
I’ve heard that as well. I’ve gotten about 5 different answers on fb pages and forums etc. some people think it could be injectors, some people think hpfp, crankshaft sensor etc. it’s always a different answer from different people lol i will definitely try to do that but the problem is idk what’s actually making it do it. Thanks for the info though I’ll get some more logs
 

Torgus

Colonel
Nov 6, 2016
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Long cranks on cold start up usually means HPFP. Which you replaced. My next bet would be the injectors. Pull the plugs. Any of them wet with fuel?

What index injectors and how old?

How old are your spark plugs and what make?

Does it do long cranks after it is warmed up or only when cold?
 
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