3.0i M54 Rough idle then cuts out

enuff_zed · Post by **enuff_zed** » Sat Dec 10, 2022 12:22 pm

Got a problem with this 3.0i that I'm trying to get through an MOT.
It has been sat for round a month without being started.
New battery, and yes my first action has been to put it on charge again overnight, just in case.

Symptoms:
1. Car starts first turn of the key, every time.
2. Sounds like it is running on about 3 cylinders and hunts around 500 to 1500 rpm
3. After about 30 seconds it gives up and dies
4. Repeats this as many times as you like, with no differences.
5. EML and engine light on
6. Traction control light on (which I believe is as a result of the engine issues)
7. If I do a fault reset with the engine running it immediately runs perfectly, for about 10 seconds, then reverts to hunting and eventually dying. This seems to possibly be as it is doing some kind of self test, and once it finds something not working it then throws faults and hunts again.

There are NO codes for misfires on any cylinders or for any O2 sensors.

I initially had these codes in the Engine Management section:
2830 DME self-test: checksum
2796 Throttle: adaptation values incorrect
28B2 Speed limitation: reset

I carried out the throttle adaptation reset, both with the Autophix and the manual way, holding the pedal down, ignition on, then off, etc.

Now, after discovering that I can get it to run cleanly if I reset while it is running I have these three codes:
2830 DME self-test: checksum
2796 Throttle actuator-test, lower stop
28B2 Speed limitation: reset

I've been googling and scaring myself with stories of dead DMEs.

Anyone got any thoughts, or come across this before?

colb · Post by **colb** » Sat Dec 10, 2022 12:37 pm

Try disconnecting the Maf so it reverts to default settings and see if it runs any better, if it's better then suspect duff Maf, they dont always set any codes in my experience. Cam and Crankshaft sensors usually set codes so probably not those playing up but check their connections are clean and tight. Usual check for air leaks in the engines vaccum system look for holes or splits in all the rubber and plastic pipes. Smoke test would help find any you can't spot visually.

enuff_zed · Post by **enuff_zed** » Sat Dec 10, 2022 12:46 pm

colb wrote: ↑Sat Dec 10, 2022 12:37 pm Try disconnecting the Maf so it reverts to default settings and see if it runs any better, if it's better then suspect duff Maf, they dont always set any codes in my experience. Cam and Crankshaft sensors usually set codes so probably not those playing up but check their connections are clean and tight. Usual check for air leaks in the engines vaccum system look for holes or splits in all the rubber and plastic pipes. Smoke test would help find any you can't spot visually.

Thanks, will definitely try those easy checks first.
It had a new inlet pipe and was running perfectly with that on.
I'm wondering if the cold spell has upset something?
The DME code is the one that worries me as everywhere I look says that means new DME!!!
Any thoughts on whether it could be the throttle body?

enuff_zed · Post by **enuff_zed** » Sat Dec 10, 2022 1:07 pm

colb, MAF made no difference.
No visual signs of any leaks. Plus it hasn't moved since it was running perfectly.
This is why I'm leaning towards electrical issues, possible damp, corrosion on connectors, or the DME.
If it wasn't so damn cold out there I'd be diving in now, but after five minutes I can't feel my fingers!

Chris_D · Post by **Chris_D** » Sat Dec 10, 2022 1:23 pm

Have you checked the CCV system condition? That sounds suspiciously like the diaphragm might have ruptured.

enuff_zed · Post by **enuff_zed** » Sat Dec 10, 2022 2:09 pm

Chris_D wrote: ↑Sat Dec 10, 2022 1:23 pm Have you checked the CCV system condition? That sounds suspiciously like the diaphragm might have ruptured.

If it had Chris, I'm not sure it would run perfectly for 10 seconds or so when I reset the faults would it?

bigwinn · Post by **bigwinn** » Sat Dec 10, 2022 2:15 pm

If it is dme issues don’t fret too much- I had that on the silver 3.0

However that manifested itself when hot….

Ista or inpa will allow a software re flash which cured mine

If that’s the actual issue

enuff_zed · Post by **enuff_zed** » Sat Dec 10, 2022 2:27 pm

I just found this which describes almost exactly what I have, right down to the same codes.
https://www.bimmerforums.com/forum/show ... p-Diagnose
Seems feasible?
The fact that two potentiometers inside the throttle body have a chat to see if they agree could explain why I get 10 seconds or so of perfect running if I reset?

enuff_zed · Post by **enuff_zed** » Sat Dec 10, 2022 2:28 pm

bigwinn wrote: ↑Sat Dec 10, 2022 2:15 pm If it is dme issues don’t fret too much- I had that on the silver 3.0

However that manifested itself when hot….

Ista or inpa will allow a software re flash which cured mine

If that’s the actual issue

Cheers Stuart, I can see this is going to get parked until the new year as I'm shortly off to warmer climes.
May well be inviting you over with your laptop in January then.

Chris_D · Post by **Chris_D** » Sat Dec 10, 2022 2:32 pm

enuff_zed wrote: ↑Sat Dec 10, 2022 2:09 pm
Chris_D wrote: ↑Sat Dec 10, 2022 1:23 pm Have you checked the CCV system condition? That sounds suspiciously like the diaphragm might have ruptured.
If it had Chris, I'm not sure it would run perfectly for 10 seconds or so when I reset the faults would it?

Could also be the throttlebody failing. I remember when mine went it ran ok with a reset and then died on the next restart.
Checked the ICV isn't sticking too?

N4LLY · Post by **N4LLY** » Sat Dec 10, 2022 2:39 pm

enuff_zed, Hope it's not DME

Are your faults reading like the one's on page one of this thread ?

viewtopic.php?p=1937550&hilit=EML#p1937550

enuff_zed · Post by **enuff_zed** » Sat Dec 10, 2022 2:43 pm

Chris_D wrote: ↑Sat Dec 10, 2022 2:32 pm
enuff_zed wrote: ↑Sat Dec 10, 2022 2:09 pm
Chris_D wrote: ↑Sat Dec 10, 2022 1:23 pm Have you checked the CCV system condition? That sounds suspiciously like the diaphragm might have ruptured.
If it had Chris, I'm not sure it would run perfectly for 10 seconds or so when I reset the faults would it?
Could also be the throttlebody failing. I remember when mine went it ran ok with a reset and then died on the next restart.
Checked the ICV isn't sticking too?

Thanks Chris.
The ICV was removed and cleaned up when I first got the car, along with a new inlet boot and an overhauled Disa. I always try to do all those while I'm in there.
A couple of posts above I linked to a bimmerforum thread which sounds identical to mine and was the throttle body.
I'm looking at that as an easier swap out than the DME first up.
Rest assured, if it turns out I've knocked the plug off I'll be so relieved that I'll happily broadcast it on here.

In fact, just to give you a laugh, with space being tight, the last thing I did before the problem occurred was reverse the car down my narrow drive and the LH wing is now about 3 inches from the wall of the house. So it's going to be fun accessing that side of the engine.

enuff_zed · Post by **enuff_zed** » Sat Dec 10, 2022 2:49 pm

N4LLY wrote: ↑Sat Dec 10, 2022 2:39 pm enuff_zed, Hope it's not DME

Are your faults reading like the one's on page one of this thread ?

viewtopic.php?p=1937550&hilit=EML#p1937550

Not quite, and it's an E85 so fingers crossed.
I'm leaning ever so slightly more towards the throttle body atm. Mainly because it looks cheaper

.

enuff_zed · Post by **enuff_zed** » Sat Dec 10, 2022 2:51 pm

What I do like about this forum is that you can bounce ideas off people even if you have a rough idea yourself.
Even though I think I 'kind of' know what it 'may' be, it is good to see other people's thoughts and if someone popped up and told me I was talking squit then I'd save myself a lot of time and expense too.

N4LLY · Post by **N4LLY** » Sat Dec 10, 2022 3:32 pm

enuff_zed wrote: ↑Sat Dec 10, 2022 2:51 pm What I do like about this forum is that you can bounce ideas off people even if you have a rough idea yourself.
Even though I think I 'kind of' know what it 'may' be, it is good to see other people's thoughts and if someone popped up and told me I was talking squit then I'd save myself a lot of time and expense too.

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