Weird cold starts - just an m3 characteristic ?

[Lozza47]

2011 E92 M3 with 130,000km

This is probably my most nooby question I've ever asked, and yes I've owned plenty of performance cars, rotaries, turbos etc but I'm honestly lost with what to think about my recently purchased m3...

Ever since purchase, I've been experiencing long crank cold starts, rough cold starts, normal cold starts, cold starts that feel like the cars about to stall, then normal cold starts again, no problems starting etc etc.
I've checked fuel and ignition, changed plugs etc but cold start is still always unpredictable.

Once the cars up and running for about 10-20 secs, everythings all well and good from here and hot starts are fine.

The cars not throwing any codes, I've checked using Carly.

There doesn't seem to be any tradition or patterns in relation to what type of cold start I get which makes it very hard to diagnose. Maybe the longer I leave the car undriven (say 24 hours plus), the cold start is roughest...

I had the rod bearings done at a bmw specialist recently and they said the car was in great condition with no major issues.

Are these rough, awkward cold starts just a characteristic of the s65?

My last option is to get the latest DME update and see what that does.

[kolosy]

i'm not sure if N(2) is enough, but i'm experiencing a somewhat similar issue. Cold starts are always long cranks. 15-20 seconds at least, and sometimes it sounds like it might not start though it always does. Only code I had was the MAF temp sensor which I replaced to no avail. Battery is recent, I replaced the plugs which looked ok, checked the starting fuel pressure (it was within ISTA's range). Not sure where to go from here either.

[Redd]

Check your ground cable?

[M3lbournE92]

Something I do to help the cold starts, I turn the ignition on twice to get the fuel pumps primed and it makes the car start a little smoother. Also I usually don't cold start the car with less than a 1/4 tank but if I do I sometimes get a little stutter so I always have at least a 1/4 or more of gas in the tank.

[m3boost]

Should instantly start, there's an issue and you need to find it.

[Redd]

Originally Posted by M3lbournE92

Something I do to help the cold starts, I turn the ignition on twice to get the fuel pumps primed and it makes the car start a little smoother. Also I usually don't cold start the car with less than a 1/4 tank but if I do I sometimes get a little stutter so I always have at least a 1/4 or more of gas in the tank.

Have u considered its a weak fuel pump?

[akkando]

Subscribed. I've been experiencing similar. Sometimes seems like it will stall on a cold start if the car has been sitting, but it never has stalled. If it's been started in let's say 24 hours or less no problems. If warm no problems.

[kolosy]

Originally Posted by M3lbournE92

Something I do to help the cold starts, I turn the ignition on twice to get the fuel pumps primed and it makes the car start a little smoother. Also I usually don't cold start the car with less than a 1/4 tank but if I do I sometimes get a little stutter so I always have at least a 1/4 or more of gas in the tank.

that's odd. ISTA has a test that shows you the fuel pressure during startup. Worth a check.

[Lozza47]

Originally Posted by Redd

Check your ground cable?

From the battery to chassis?

[SilverSlug]

Some people have reported longer starts before the throttle actuators going out (one of the ticking time bombs on these majestic beasts).

Also, +1 on starting procedure of pressing the start button twice (and letting the cluster needles illuminate) in order to prime the fuel pump before pressing the clutch and starting the engine (you can hear the buzzing then it stops).

Long start could also be leaky or dirty injectors, or failing coil pack.

[Lozza47]

So I've found a trend, the cold starts seem to be a bit more erratic the lower the fuel reads. I start to get close to stall and longer cranks as the marker reads below quarter tank.
Anything I should look at based on this?

[SilverSlug]

When it finally starts does it idle nice and steady or is it erratic at all?

[Lozza47]

Originally Posted by SilverSlug

When it finally starts does it idle nice and steady or is it erratic at all?

Erratic up and down (kinda sounds cammed) sometimes close to stall but only for up to 10 seconds. After that it smoothes out and haven't had any issues, taken it track recently as well.

[SilverSlug]

Erratic idle like that could be a faulty fuel breather valve (part# 13907838281).

It's located below the plenum. Pretty easy to replace.

[tdott]

Originally Posted by Lozza47

My last option is to get the latest DME update and see what that does.

Try that.

My car ran with a slight miss but no codes since I bought it. I updated to 241E after doing plugs and didn't fix it and it threw a mis fire code on the first drive. I swapped the coil and it moved. So a new coil and runs great now.

[SilverSlug]

Originally Posted by tdott

Try that.

My car ran with a slight miss but no codes since I bought it. I updated to 241E after doing plugs and didn't fix it and it threw a mis fire code on the first drive. I swapped the coil and it moved. So a new coil and runs great now.

So is the 241E software different from having a tuning map installed?

If I already have Dinan software, will 241E overwrite the Dinan map?

Or is 241E a firmware update that won't impact the Dinan map I currently have?

[MacGruber]

https://www.m3post.com/forums/showthread.php?t=1260198

This is something to have a read of. I recently discovered that Shell petrol for me ruins my cold start significantly but BP and Mobil runs great. Something to keep in mind at least and it doesn't really cost anything which is nice

[Lozza47]

Originally Posted by MacGruber

https://www.m3post.com/forums/showthread.php?t=1260198

This is something to have a read of. I recently discovered that Shell petrol for me ruins my cold start significantly but BP and Mobil runs great. Something to keep in mind at least and it doesn't really cost anything which is nice

Interesting, I only use Shell.
I'll try a different brand and report back.
I will also be doing the DME update in the next couple of weeks.

[serranot]

Do these cars have an in tank fuel filter on the pump?

I once had a car that ran worse and worse as the tank got lower. Turned out to be a plugged fuel pump filter.

[SilverSlug]

Why Shell?

I use only Chevron gas. It has an additive called Techron, which is a great fuel injector/system cleaner.

[tdott]

Originally Posted by SilverSlug

So is the 241E software different from having a tuning map installed?

If I already have Dinan software, will 241E overwrite the Dinan map?

Or is 241E a firmware update that won't impact the Dinan map I currently have?

Usually tuners base their tunes off the latest version. But it might depend on when the car was tuned and that specific tuner. Not sure what Dinan uses.

[dpaul]

Originally Posted by SilverSlug

So is the 241E software different from having a tuning map installed?

Yes "241E" refers to an OEM update that changes both "tune" (aka calibration data) and "program" areas in DME memory. The "tune" contains lists and tables of parameters like spark advance at a given load and rpm etc while the "program" is the executable that actually runs the engine. Like virtually all tunes, the heart of the Dinan software is about the calibration data. Some changes in program areas may be made to a) overcome factory protection against writing non-OEM calibration files and b) make it difficult to read out (i.e. 'steal") the tune. But for the most part, program operation is not altered. Most tuners require the program software to be updated to a later version of the factory software (240E or 241E) - their calibration files would not function correctly with earlier versions (i.e. 231E, 160E etc)

Originally Posted by SilverSlug

If I already have Dinan software, will 241E overwrite the Dinan map?

Or is 241E a firmware update that won't impact the Dinan map I currently have?

Yes, if 241E is flashed to your DME, both program and calibration data are completely replaced. The Dinan software will be completely overwritten and permanently lost.


BUT TO RETURN TO THE OP's TOPIC
I've been experiencing this same long crank/idle stumble during the 1st minute after cold start as others have reported here.

- It developed over the past year (i.e. was not always this way)
- It takes 5-10 seconds of cranking before engine catches
- Battery is relatively new and cranking speed is excellent
- Long cranks are only experienced from a stone cold start
- There's a major stumble in idle about 10-20 seconds after it starts
- Idle is somewhat rough for a few minutes but it never stalls
- Engine operation is completely normal once warm
- There are no codes whatsoever
- The behavior is not affected by fuel level in tank.

Thinking fuel pressure issues on startup might explain it, I put a fuel pressure gauge in line - pressure instantly goes where ISTA documentation says it should. Significant pressure is maintained overnight.

I coded out the cold start sequence which eliminated the stumble 10-20 seconds after startup but did not affect the long crank.

TAs and ICV are expensive and I am reluctant to replace them on spec without any supporting codes. In any case, I can't see why TA/ICV problems would only affect cold start.

Any ideas?