E46 M3 Cold Start Hesitation, Cant Find The Solution?

[Tomba]

I do a lot of ECU modifications to racing cars with S54B32 with stock ECUs and this starting behavior on the first video is not normal. All cars that I work on fire up within a blink and idle perfectly, even with large duration camshafts. I can only suggest that the amount of fuel to prime the intake and cylinders isn't enough to make the engine idle smoothly upon start up. I would check injector flow (static & dynamic) and spray pattern first. Also observe the coolant and air intake temperature before starting. Large deviations can indicate a problem with these sensors and might results in less or too much fuel during start up. Fuel adaptations would be welcome to.

[S54B32]

As Terra showed in his video, even a ~200k miles M3 should fire up normal. And if someone says his M3 doesn’t fire up on first crank or has a very bad cold start (since x miles or even from factory) there IS a fault or defective part. period. This is definitely no „normal“ behavior.



I bought recently another E46 M3 that has exactly this behavior (only on cold start in the morning, first a short crank, than another crank to fire it up and a bit rough idle after start up and very rare i need multiple cranks).

I cleaned/serviced the injectors and the problem went away for 5-6 cold starts and now it’s back.
I could never live with a issue like this, so I will continue the search and post here when I made progress.

[Nate047]

My car does the exact same thing. I usually crank it for a sec, let go, and crank it again and it starts up fine.

[DropTopKingM3]

M3S54E46 is your car doing the same thing as mine?

[Andy2424]

In conjunction with a software adaptation, the mixture is changed during a cold start and the car becomes drivable for the first few meters. Of course, this does not comply with the law ...

If you unplug the pump, what happens after a cold start?

[sapote]

I've had it in there for a long time, it only helps a little.

This is due to the enrichment during a cold start ... Removing the secondary air pump is a solution.

I thought the secondary air pump is only for heat up the catalytic converter quicker, so why delete it helped solving your problem?

[Andy2424]

Maybe this is a solution.

https://www.probsten-tech.de/z4mm3-s54-kaltstart-magerruckelloesung/

This is more for the Z4M but its way similar to the E46 m3

I translate it for you.

"Many Z4M drivers will notice that the starter always has to turn for different lengths of time in the morning, which is not normal. Sometimes it takes an extremely long time and you can also perceive one or the other weak combustion, which is not enough for the engine to start up. The engine was probably tuned so lean for the emissions tests that the first injections for some engines in the series spread are no longer rich enough. The entire first series of injections goes unburned into the exhaust gas or through the cylinder walls into the oil."

I've had it in there for a long time, it only helps a little.

This is due to the enrichment during a cold start ... Removing the secondary air pump is a solution. Adapting the software to this.

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/47528-cold-start-gremlin

[terra]

Not really. I don't think it's much of a problem.



By any chance did you adjust your idle speed?

I bumped it up a hair when I installed Schrick cams, though the speed you see there is representative of the cold start behavior. It'd come down to about 920 when warmed up (instead of 870 stock)

[elbert]

Then you potentially stand to benefit the greatest from this fix!

Not really. I don't think it's much of a problem.

This is my 199k mile m3

By any chance did you adjust your idle speed?

[terra]

Maybe this is a solution.

https://www.probsten-tech.de/z4mm3-s54-kaltstart-magerruckelloesung/

This is more for the Z4M but its way similar to the E46 m3

I translate it for you.

"Many Z4M drivers will notice that the starter always has to turn for different lengths of time in the morning, which is not normal. Sometimes it takes an extremely long time and you can also perceive one or the other weak combustion, which is not enough for the engine to start up. The engine was probably tuned so lean for the emissions tests that the first injections for some engines in the series spread are no longer rich enough. The entire first series of injections goes unburned into the exhaust gas or through the cylinder walls into the oil."

If it's truly an issue of being too lean on cold starts, that would be fairly trivial to fix... but that doesn't really explain why most cars seem to start without any sort of issue.

[jbfrancis3]

In my case it did come that way from the factory. And I would know since I am the only owner.

Then you potentially stand to benefit the greatest from this fix!

[enjoy_m3]

check fuel pressure, it's probably not building enough pressure.

[terra]

This is my 199k mile m3

[ATB88]

Maybe this is a solution.

https://www.probsten-tech.de/z4mm3-s...ruckelloesung/

This is more for the Z4M but its way similar to the E46 m3

I translate it for you.

"Many Z4M drivers will notice that the starter always has to turn for different lengths of time in the morning, which is not normal. Sometimes it takes an extremely long time and you can also perceive one or the other weak combustion, which is not enough for the engine to start up. The engine was probably tuned so lean for the emissions tests that the first injections for some engines in the series spread are no longer rich enough. The entire first series of injections goes unburned into the exhaust gas or through the cylinder walls into the oil."

Huh! This, elbert's, and AvusM5's posts are all very interesting in that they suggest my engine's current startup behaviour is more or less normal! Even more interestingly, some cars have it from the start, and some, like mine, suddenly develop it out of the blue. Even if the answer is of no practical consequence, I remain very curious as to what exact change in my car's configuration brought this about. But I guess I'm starting to feel a little better that my engine isn't a dud?

[Christian_M3]

Maybe this is a solution.

https://www.probsten-tech.de/z4mm3-s54-kaltstart-magerruckelloesung/

This is more for the Z4M but its way similar to the E46 m3

I translate it for you.

"Many Z4M drivers will notice that the starter always has to turn for different lengths of time in the morning, which is not normal. Sometimes it takes an extremely long time and you can also perceive one or the other weak combustion, which is not enough for the engine to start up. The engine was probably tuned so lean for the emissions tests that the first injections for some engines in the series spread are no longer rich enough. The entire first series of injections goes unburned into the exhaust gas or through the cylinder walls into the oil."