N54 Idle Surge? Help needed

N54savage

Lurker
Aug 11, 2020
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Check codes. What’s the maintenance history on the car?

I checked for codes there’s no codes or although there was a shadow code (2FDB Crankshaft Sensor, signal; not plausible). I has not come back since I cleared it.
Car recently had intake valves cleaned with me NGK spark plugs. All maintenance has been done as required.
 

Jeffman

Captain
Jan 7, 2017
1,471
525
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Sorry, guy. I’m not familiar with your units. You say “all maintenance is done as required.” What does this mean? How many miles? What’s your setup? What are the mods? What injectors? Spark plugs? Etc. When were the new parts installed? Etc.
 
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N54savage

Lurker
Aug 11, 2020
23
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Sorry, guy. I’m not familiar with your units. You say “all maintenance is done as required.” What does this mean? How many miles? What’s your setup? What are the mods? What injectors? Spark plugs? Etc. When were the new parts installed? Etc.

Car has about about 130k Miles, Stage 2 MHD tune with downpipes and intake. 6 speed manual.
I never had much problems with the car.
injectors are index 6/7. I don’t have any long crank issues. No misfire codes.

within the past 5k miles
-Intake Valves Cleaned with new intake manifold gasket and throttle body gasket
-NGK 1 step colder spark plugs
-New filter

20k miles,
- valve cover gasket
-oil pan gasket
-upgrade PCV valve
-oil cooler and housing gasket
-vacuum lines

40k miles,
-turbos
-clutch.

I haven’t done coil packs, injectors or HPFP. They seem to functioning correctly.

thank you
 

N54savage

Lurker
Aug 11, 2020
23
2
0
I had a similar issue and it was a bad Throttle body. Replaced it with a used ebay one and it fixed my issue. I only had 70K on the car at the time.
Thank you, I’m going see if I can find a throttle body.

Car started to stall out during idle now and it’s not throwing any codes. I just don’t want start replacing parts without having a good idea of the cause of the problem.
If I can find a good used throttle body I will try swapping it.
 

Slideways-inc

New Member
Oct 14, 2020
6
3
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Thank you, I’m going see if I can find a throttle body.

Car started to stall out during idle now and it’s not throwing any codes. I just don’t want start replacing parts without having a good idea of the cause of the problem.
If I can find a good used throttle body I will try swapping it.
Have you tried to reset throttle adaptations ?
 
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RTA

Lurker
Jun 17, 2020
10
5
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Fuel pump, injector and yes give the reset throttle adaption a try, given your replacement. (do it right, otherwise you idle will be all over the place, it should at least be in the state as before your throttle body replacement)

You will most often not get a code when fuel issues causing an instable idle.
Another thing is to take your plugs out in the morning, check if one of them is wet, if so -> Injector leak...
Anyway, hpfp, lpfp, fuel sensor, injectors are my suspects.. there is quite some tolerance before you get a code. You could also gently warm up the car and do a brief full throttle on the high way in 3rd/4rd coming from 2k revs or so, this will give some pressure in the system and in case fueling is off, this will throw you an error. Keep it brief and controlled because flooring a car with issues is never the best thing to do, but in this case you might be able to pull a code.
 
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RTA

Lurker
Jun 17, 2020
10
5
0
O2 sensors, plugs and candles could also cause the issue, my experience heavy idle instability = often fuel related or maf / o2 sensors, minor instability plugs, o2 in the process of failing, candles.. but there is no hard science behind this..
 
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N54savage

Lurker
Aug 11, 2020
23
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Fuel pump, injector and yes give the reset throttle adaption a try, given your replacement. (do it right, otherwise you idle will be all over the place, it should at least be in the state as before your throttle body replacement)

You will most often not get a code when fuel issues causing an instable idle.
Another thing is to take your plugs out in the morning, check if one of them is wet, if so -> Injector leak...
Anyway, hpfp, lpfp, fuel sensor, injectors are my suspects.. there is quite some tolerance before you get a code. You could also gently warm up the car and do a brief full throttle on the high way in 3rd/4rd coming from 2k revs or so, this will give some pressure in the system and in case fueling is off, this will throw you an error. Keep it brief and controlled because flooring a car with issues is never the best thing to do, but in this case you might be able to pull a code.
Thank you for your advice. I will definitely look into fueling. I did try WOT pulls and it did not throw any codes.
Would the EKP module cause idle issues? I have an early N54.
What I find weird is that my car did not throw a code even when one of the diverters valves popped off the charge pipe and had a huge boost leak.
 

N54savage

Lurker
Aug 11, 2020
23
2
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I replaced the coilpacks to rule that out and I'm still having the issue. Checked the spark plugs to after letting the car sit over night and they are not wet with fuel.

Probably look at replacing the Low pressure fuel sensor next, then the HPFP.
 

TheFixer

Corporal
Aug 16, 2020
207
91
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Tennessee
Ride
2008 535i, my wife
I skimmed through this, forgive me if I overlooked a suggestion. Fuel filter under the rear seat opposite of the fuel pump can cause poor running issues. Clogged up or they get cracks in them and you loose pressure.
 
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