Idle Problem - Can anyone help?

[325_bucks]

Sorry for the long post, appreciate anyone reading to give me advice...

Hi all

Imposter here from the M6 side, but that side is quite quiet so I hope you don't mind me asking here as it's going to be relevant to both.

As short as I can - purchased F13 M6 couple months ago, great car, mildly tuned but not engine itself, just intake really. Runs great in general and being new to this engine/car I didn't notice anything terrible on the test drive. One thing I have done since ownership is do a cold start delete which has served to highlight this issue more, but I'm 99% sure the issue was there all along.

So, the issue - On cold starts, i.e. when starting after sitting overnight, id seems to start and rev correctly. Then after about 20 seconds, it starts idling roughly, the revs drop and then it recovers by surging and then this repeats a number of times, for about 30-45 seconds. Here is a clip I recorded the other day, sometimes it's worse, but this gives a good idea. Please watch with sound too

https://www.youtube.com/watch?v=UXlJaj0tL6k

When the revs drop you feel it in the car. When trying to drive during this time it kangaroos like crazy, I have to wait for it to settle.

Until recently I thought it was only during startup but now I think that when I come to a stop at any time, the idle is not as smooth as it should be, the needle does move slightly and what's even weirder is that when creeping along before stopping, as soon as I brake the revs go up over 1k quickly then quickly drop back down. All a bit strange. (that part could be normal though).

All I have done so far mechanically is a MAF sensor change.

In terms of mapping, I have been running Bootmod3 however I am currently back on the stock tune and it's still doing it. With the cold start function ON, although the revs are higher, they are still not stable like I would expect, though its less noticeable than with cold start off I admit.

Oh an no error codes are thrown at all.

Basically looking for advice on next steps. I have ISTA, should I be looking at doing any specific diagnostics tests?

My next action is to replace plugs and coils because I just like to know they are refreshed, but I'm not just assuming that will fix my problem.

Any advice would be great as it's one of 2 issues that are ruining the enjoyment a little (I'll post the other one separately!)

Thanks for reading

[Blaxwil]

Try cleaning the MAF's with MAF Cleaner. This will most likely solve your problem immediately.

[JBala84]

Originally Posted by 325_bucks

Sorry for the long post, appreciate anyone reading to give me advice...

Hi all

Imposter here from the M6 side, but that side is quite quiet so I hope you don't mind me asking here as it's going to be relevant to both.

As short as I can - purchased F13 M6 couple months ago, great car, mildly tuned but not engine itself, just intake really. Runs great in general and being new to this engine/car I didn't notice anything terrible on the test drive. One thing I have done since ownership is do a cold start delete which has served to highlight this issue more, but I'm 99% sure the issue was there all along.

So, the issue - On cold starts, i.e. when starting after sitting overnight, id seems to start and rev correctly. Then after about 20 seconds, it starts idling roughly, the revs drop and then it recovers by surging and then this repeats a number of times, for about 30-45 seconds. Here is a clip I recorded the other day, sometimes it's worse, but this gives a good idea. Please watch with sound too

https://www.youtube.com/watch?v=UXlJaj0tL6k

When the revs drop you feel it in the car. When trying to drive during this time it kangaroos like crazy, I have to wait for it to settle.

Until recently I thought it was only during startup but now I think that when I come to a stop at any time, the idle is not as smooth as it should be, the needle does move slightly and what's even weirder is that when creeping along before stopping, as soon as I brake the revs go up over 1k quickly then quickly drop back down. All a bit strange. (that part could be normal though).

All I have done so far mechanically is a MAF sensor change.

In terms of mapping, I have been running Bootmod3 however I am currently back on the stock tune and it's still doing it. With the cold start function ON, although the revs are higher, they are still not stable like I would expect, though its less noticeable than with cold start off I admit.

Oh an no error codes are thrown at all.

Basically looking for advice on next steps. I have ISTA, should I be looking at doing any specific diagnostics tests?

My next action is to replace plugs and coils because I just like to know they are refreshed, but I'm not just assuming that will fix my problem.

Any advice would be great as it's one of 2 issues that are ruining the enjoyment a little (I'll post the other one separately!)

Thanks for reading

I had/have a very similar issue... only on start up.
As per the previous post, I would suggest cleaning the MAF (both).
It seemed to have solved the issue for me for a while, but recently I am getting the erratic revs again.
I put the car on the computer and all was perfect.
So barring changing the MAF, I am lost.

[325_bucks]

Hmmm yeah I’ve unfortunately already changed my mafs. It’s quite frustrating

[JBala84]

Originally Posted by 325_bucks

Hmmm yeah I’ve unfortunately already changed my mafs. It’s quite frustrating

I think it's best to ask the 'professionals'...
Personally I would try and find a independent M specialist to get their opinion.
Defo a concern when nothing is showing on the computers...
Keep me posted.

[M6Roar]

Does the RPM drop to below 500rpm when stopping nearby a traffic light? or after keeping the car on for a while? or when you turn the steering wheel to the max(left or right doesn't matter) in a stationary position?

[325_bucks]

Originally Posted by M6Roar

Does the RPM drop to below 500rpm when stopping nearby a traffic light? or after keeping the car on for a while? or when you turn the steering wheel to the max(left or right doesn't matter) in a stationary position?

drops on hard lock left or right, surges when coming to a stop and drops when actually stopping. I've done a lot more work on this and still not come up with the answer

[M6Roar]

Share WOT datalog but from past experience, there is a slight air leak.

If you ever changed the filters or removed the airbox check the boots as they have guides it may not be seated correctly, check your charge pipes and using BM3 keep your cold start at 1100 RPM.

Also, reset adaptations & relearn Valvetronic limit position through ISTA.

[325_bucks]

Originally Posted by M6Roar

Share WOT datalog but from past experience, there is a slight air leak.

If you ever changed the filters or removed the airbox check the boots as they have guides it may not be seated correctly, check your charge pipes and using BM3 keep your cold start at 1100 RPM.

Also, reset adaptations & relearn Valvetronic limit position through ISTA.

Thanks M6Roar, couple of quick questions. Air leak seems like a good next step to check considering every other part has been changed.

I don’t think the boots are not fitted correctly but I wasn’t aware of them having guides, is that on both sides?

Setting cold start rpm does not appear to work and BM3 are aware, basically setting the rpm still carries out a cold start as normal, but more quickly dips down so it doesn’t respect the setting on this car it seems.

I reset the adaptations a number of times and have also relearned the valvetronic positions (I think) but I could try again.

What is the best way other than visibly to check the charge pipes and also, do you know where the best place to insert smoke would be to conduct a leak test on the vacuum side?

Finally BM3 suggested there could be a leak between turbos and downpipes. What’s the best way to test for that?

Sorry for all the questions!

[M6Roar]

Originally Posted by 325_bucks

Thanks M6Roar, couple of quick questions. Air leak seems like a good next step to check considering every other part has been changed.

I don’t think the boots are not fitted correctly but I wasn’t aware of them having guides, is that on both sides?

I didn't think that too until I saw them lol, the have groves on the side that goes to the turbo

Setting cold start rpm does not appear to work and BM3 are aware, basically setting the rpm still carries out a cold start as normal, but more quickly dips down so it doesn’t respect the setting on this car it seems. When you change the cold start rpm to custom and choose your preferred RPM, it doesn't work? weird mine is fully functioning

I reset the adaptations a number of times and have also relearned the valvetronic positions (I think) but I could try again.

What is the best way other than visibly to check the charge pipes and also, do you know where the best place to insert smoke would be to conduct a leak test on the vacuum side? Usually the intake

Finally BM3 suggested there could be a leak between turbos and downpipes. What’s the best way to test for that? Do you hear uneven note between the exhaust9? there is an option in ISTA to fully close the waste gate

A data log will answer a lot of questions (both dmes)

Sorry for all the questions!

In my case I had the same issue and I went crazy tbh. Replaced seals including the turbo dp ones, parts etc and nothing helped I even replaced the boost solenoids and guess what one day I was on WOT and decided to open the bonnet and found trace of meth on the coolers(leaking from the silicon connection & the intake boots were not seated correctly. Problem solved!