[Jester236]

Hello,

Need some help determining if this is normal function or not. 2019 M5 Competition

On cold start I have no issues. It idles high for about 10 seconds as expected then drops down to normal and holds it without issue.

Once warm, when coming to a stop the idle will drop to normal but occasionally have a slight up/down fluctuation by around 100 rpm.

On hot start (typically after dropping my daughter off at day care, so about 5 mins between stop/start) it will have an immediate rough idle bouncing up and down by 150-200 rpm for about 5 seconds before stabilizing.

Trying to determine the cause/if this is just expected behavior. I previously had a 2018 M5 non-Comp and I don't remember this being an issue.

The car has already had the Low Pressure Fuel Pump replaced for the notorious stalling/hard start issue, that was only around 3k miles ago.

It also had the valve cover gaskets replaced due to finding oil in the spark plug wells on the drivers side. Passenger side was clean.. After that I replaced the front 3 coils on the drivers side due to the oil leak. Did not replace the 4th (closest to the steering wheel) as it showed no signs of oil in the spark plug well. All 8 plugs were replaced about 3k miles ago as well.

I have already ordered a new coil/plug for that 4th cylinder since it's < $100 and easy to do myself. I've also run two tanks of gas with Techron fuel injector cleaner through with no visible changes.

It has had a Racechip on Map 7, however I took that off completely this evening to eliminate it as the source however the problem persisted.

The car did have a slightly leaking coolant tank that was replaced about 500 miles ago, no obvious damage to injectors/coils/etc. though it can't be ruled out completely that injectors weren't damaged. Can't imagine the new coils were damaged that badly in the short amount of time they were run while it was leaking based on the volume, though could be wrong.

Am I crazy here and maybe this is just normal? Do you guys get a rock solid idle on hot startup? Hoping replacing this coil may help but not optimistic and wanted to get some opinions before I try to have a shop track it down.

Thanks!

[AHall]

No idle fluctuations at all. I do not have any modifications or repairs after 2+ years.

[carseatsm5]

No idle issues here in three years of ownership. Had a leaky coolant tank replaced earlier this year.

[jm490]

Now that you mention it I have a weird idle issue but ONLY when Im filling up gas. So now I turn my car off when Im filling up.

Im not sure what it is but the car almost stalls and then like jumps a little faster then goes back to a normal idle after that 4-5 second weird idle.

Anyone ever have that issue?

[AHall]

Originally Posted by jm490

Now that you mention it I have a weird idle issue but ONLY when Im filling up gas. So now I turn my car off when Im filling up.

Im not sure what it is but the car almost stalls and then like jumps a little faster then goes back to a normal idle after that 4-5 second weird idle.

Anyone ever have that issue?

I was taught long ago to turn the car off when pumping gas, so I would not know. Maybe modern cars do not have the same sources of ignition which were thought to be a source of ignition of the gas vapors.

[ResIpsaLoquitur]

Originally Posted by jm490

Now that you mention it I have a weird idle issue but ONLY when Im filling up gas. So now I turn my car off when Im filling up.

Im not sure what it is but the car almost stalls and then like jumps a little faster then goes back to a normal idle after that 4-5 second weird idle.

Anyone ever have that issue?

Can confirm that this happens each and every single time I fill up with the engine running, right around the 50% capacity mark, regardless of how much fuel was in the tank prior to starting filling up.

I know it’s better to turn the car off, but sometimes I don’t want to.

[Jester236]

Thanks for the feedback everyone. Fill up issue aside it sounds like what I'm experiencing is not normal. Fingers crossed this coil pack does the trick.

[micvite]

Originally Posted by Jester236

Thanks for the feedback everyone. Fill up issue aside it sounds like what I'm experiencing is not normal. Fingers crossed this coil pack does the trick.

The minor idle fluctuations are normal, running rough for a few seconds is not normal.

[XX - M5 - XX]

I have the same issue. Have had the car for 5 months. Happens a few times a week. Not tied to refueling, as I always have car off at that point. It happens sometimes when the car is warm and it was off, and I restart it. Also happens when I'm driving and come to a stop for a few seconds. No history of service tied to fueling issues. Replaced spark plugs and ignition coils a month ago and it still happens just as much.

[Nikolov]

My wife's M5 does the same. It doesn't do it on every start and it only happens when the car is hot. The car has had the coolant tank replaced twice now and all the injectors and coils on that side, due to coolant leaking on them. That hasn't fixed it

[Jester236]

Is there any kind of MAF sensor that could be dirty and causing it? After replacing my last coil and plug it still appears to be present on mine, though I've only driven it a few miles.

[hookson]

Originally Posted by Jester236

Hello,

Need some help determining if this is normal function or not. 2019 M5 Competition

On cold start I have no issues. It idles high for about 10 seconds as expected then drops down to normal and holds it without issue.

Once warm, when coming to a stop the idle will drop to normal but occasionally have a slight up/down fluctuation by around 100 rpm.

On hot start (typically after dropping my daughter off at day care, so about 5 mins between stop/start) it will have an immediate rough idle bouncing up and down by 150-200 rpm for about 5 seconds before stabilizing.

Trying to determine the cause/if this is just expected behavior. I previously had a 2018 M5 non-Comp and I don't remember this being an issue.

The car has already had the Low Pressure Fuel Pump replaced for the notorious stalling/hard start issue, that was only around 3k miles ago.

It also had the valve cover gaskets replaced due to finding oil in the spark plug wells on the drivers side. Passenger side was clean.. After that I replaced the front 3 coils on the drivers side due to the oil leak. Did not replace the 4th (closest to the steering wheel) as it showed no signs of oil in the spark plug well. All 8 plugs were replaced about 3k miles ago as well.

I have already ordered a new coil/plug for that 4th cylinder since it's < $100 and easy to do myself. I've also run two tanks of gas with Techron fuel injector cleaner through with no visible changes.

It has had a Racechip on Map 7, however I took that off completely this evening to eliminate it as the source however the problem [...]

I have EXACTLY the same problem. I haven’t been able to figure it out yet. 40000 miles M5C 2019. Idle is also kind of rough time to time and you can feel it. Although I can’t see any misfires in BimmerLink.

On those hot rough starts I will usually see 1-2 misfire. Usually one of them will be in cylinder 5, that has the weakest compression in my whole engine on the driver bank.

5 166 psi 11.44 bar
6 173 psi 11.93 bar
7 181 psi 12.48 bar
8 180 psi 12.41 bar

Plugs new, coolant take replaced. Ignition coils are old, as well as most of the injectors, although I have new injector in cylinder 5.

I don’t think it’s normal but I can’t solve it for now. I know few more cars that have similar pattern. Most of them are 2019 M5C.

[hookson]

Originally Posted by Jester236

Is there any kind of MAF sensor that could be dirty and causing it? After replacing my last coil and plug it still appears to be present on mine, though I've only driven it a few miles.

No MAF on S63TU4.

[hookson]

I have theory that that this can be caused by incorrect/abnormal fuel pressure in the system.

Because I have a feeling it actually started to happen after LPFP replacement.
Before the car would just stall under those “hot rough start” conditions.

Now instead of stalling, we get this fluctiating RPM on hot start. Again, that’s just a theory…

[Desking101]

This may sound silly, but have you checked your air filters? These cars are very sensitive to dirty filters

[hookson]

Originally Posted by Desking101

This may sound silly, but have you checked your air filters? These cars are very sensitive to dirty filters

Unfortunately, they are new.

I am pretty sure the OP is experiencing the same thing as in my video.

https://share.icloud.com/photos/045Z...N_lhwP_a-mGuVg

[hookson]

And since some people mention they have idle fluctuations when fueling (I never run engine when doing so, so can’t tell), isn’t it the same scenarios where LPFP fuel flow is directly affected…?

[Jester236]

Originally Posted by hookson

Unfortunately, they are new.

I am pretty sure the OP is experiencing the same thing as in my video.

https://share.icloud.com/photos/045Z...N_lhwP_a-mGuVg

This is EXACTLY what my RPM's do as well on hot start.

Air filter is essentially brand new, replaced 1-2k miles ago.

Only thing I could think to try now are injectors but those are more expensive and involved.

[Nikolov]

Originally Posted by Jester236

This is EXACTLY what my RPM's do as well on hot start.

Air filter is essentially brand new, replaced 1-2k miles ago.

Only thing I could think to try now are injectors but those are more expensive and involved.

Same, my wife's M5 is sometimes worse. According to her it has stalled once, I rarely drive her car and it has never stalled on me, but I've seen the rpm fluctuate even worse sometimes - '19 M5C ('18 prod date). The LPFP hasn't been replaced, but we've had 2 expansion tanks replaced and both times they also replaced injectors and coils on that side, so it's not the injectors or coils.

[hookson]

Originally Posted by Nikolov

Same, my wife's M5 is sometimes worse. According to her it has stalled once, I rarely drive her car and it has never stalled on me, but I've seen the rpm fluctuate even worse sometimes - '19 M5C ('18 prod date). The LPFP hasn't been replaced, but we've had 2 expansion tanks replaced and both times they also replaced injectors and coils on that side, so it's not the injectors or coils.

I don’t understand what can be the reason for such fluctuations then…

[Jester236]

Same, debating seeing if my local indie mechanic can track it down but not sure if it's worth the cost. Feel a bit better knowing it's not just me and it might just be minor but common issue.

[Eljeffrey13]

My car has the same issue, alittle rough at start up only sometimes tho, and idle goes up and down maybe 100-200rpm but again once in awhile.. i have brought it to the dealer acouple times, they say everything is fine, lpfp is good and no faults, my SA also said that the shop forman said it was normal with this engine