M54 2.5 hesitation and slight rough idle

[bigwinn]

Afternoon all

Got a very slight rough idle and a misfire on acceleration when on low power/revs

Done a load of stuff anyway so the diagnosis goes on:

New coils
New sparks
New MAF
Checked for air leaks (do need to get it smoke tested to see if it’s CCV based)

Ran some redex through
Gave it an Italian tune up

Still there

Screens from INPA for info- anyone seeing anything?

I noticed a few bits on the injector screen? Cyl 4?

 

[Rucky]

I think you may have answered your own question,
"laufunruhe" - rough running #4 possibly ?

 

[axelleveau]

Hi Stuart,

I had a look at your pictures (with some help from a translation tool ), and cannot see anything obviously wrong.

Do you know what that "irregular running" screen actually is? I translated "laufunruhe" and got "Rough Running" so I am not having much help there. Is there a chance you could record while driving the car to reproduce that misfire issue?

 

[axelleveau]

I think you may have answered your own question,
"laufunruhe" - rough running #4 possibly ?

Rucky, I agree with you this feels like a strong hint but I am surprised the car would pick up an irregular combustion on that cylinder despite the fact Bigwinn has replaced coils and plugs. I am also wondering what a "rough running" actually is supposed to be :|
Then an airleak issue would likely be on all cylinders. That could leave a fuel issue, potentially injector, but it would be worth having more logs before looking at it.

 

[axelleveau]

Sorry guys for flooding the thread but google gave me an answer: The rough running values are based on the flywheel acceleration each of the cylinder delivers (pretty clever things the software can do with limited sensors), you can read more here: https://www.bimmerforums.co.uk/threads/inpa-engine-roughness-test-anyone-know-exactly-what-it-is.121475/

So it does seem cylinder 4 is deviating from the rest (probably not burning as well), even though it is far from reaching the red gauge. It can be due to lots of reasons though :thumbsdown:

 

[bigwinn]

Cheers lads- I keep looking at 4 wondering whether it’s an injector issue, I’ve got some spares I can swap out

Great shout on the air leaks- I should have realised that it would affect all not just one

See- that’s what the forum is good for and I’m still figuring out how inpa works!

 

[bigwinn]

If I do replace an injector do M54 injectors need ‘coding’ to the car?

Seen later cars do need the flow rate entering

 

[enuff_zed]

If I do replace an injector do M54 injectors need ‘coding’ to the car?

Seen later cars do need the flow rate entering

How much hassle is it to swap two over in the car. Definitely no need for coding then and can see if the fault moves.

 

[bigwinn]

Took the injectors out of the scrapper v easily

 

[bigwinn]

I had some spare injectors- replacing numbers 4 and 5 which looked the poorest operating does seem at this point to have solved the stuttering under load

I’ll keep posted

 

[Bumwah]

I had a problem with the brake servo. It was a vacuum leak and caused irratic tick over and ran very lumpy.
Just another suggestion for you. Hope it helps.

 

[bigwinn]

I had a problem with the brake servo. It was a vacuum leak and caused irratic tick over and ran very lumpy.
Just another suggestion for you. Hope it helps.

Thanks bud will have a look at that too

 

[bigwinn]

Revisiting this

90% better but the missing low end still when engine gets hot- takes about 30 mins of driving for it to come back

Looked at inpa again and it’s showing poor running on 4 5 and 6

Worth looking at lamda sensors next?

Stuart

 

[dwoodford1987]

Have you done the valve cover gasket?

 

[bigwinn]

Have you done the valve cover gasket?

yep new one fitted