E46 M3 Cold Start Hesitation, Cant Find The Solution?

[M3S54E46]

Hello Everyone I am new to this forum,

My e46 m3 has been hesitating on cold starts (please watch the VIDEO), the rpm's jump several times to the correct rpm rather then being smooth. The car then idles very smoothly afterwards. I was hoping to get some feedback if anyone has ever seen something similar to that video, or could recommend anything to help solve this issue. The car has roughly 67k miles.

Also here are some important points

• The car is throwing no error codes
• The car starts great when warm (any heat in engine)
• Car starts every-time when cold on first try (just hesitates usually)
• Car starts better if it doesn't sit very long, however it can start poorly even when started the next day..
• Car drives great, no hesitations when driving
• ICV & throttle bodies cleaned (seems to have had no effect on starting issue)
• Compression test numbers were even across cylinders (measured warm)
• Brand NEW Battery
• Valve adjustment & Vanos rebuilt complete
• New Spark Plugs
• New Fuel Filter

I think this issue is most likely either the Injectors not working optimally, or maybe the fuel pump going bad? I think my best bet is to do a fuel pressure test and see the results. The car does not have any issues other then the cold start.

Thanks everyone!

[sapote]

Normal for these cars.

[BigLooga]

Hi, i have been having this exact problem for the past 2 weeks, only cold starts, it happened about 2 weeks ago and got progressively bad, at first a little stumble, then a bit more and then today it started and died but after a quick restart it's perfect. Zero other symptoms.

M354E46, have you figured it out?

I've owned this car for almost 8 years and it never did that, ever so i don't think it's "normal" for these cars, my opinion.

[ATB88]

Interestingly: this behaviour is in some cases similar to my car's rough-start behaviour (see here: https://nam3forum.com/forums/forum/m...ts-please-help), except my problem is actually usually on warm starts rather than cold (might have equal likelihood for both, but I warm-start my car far more often than cold). My rough starts are sometimes rougher, but in milder cases seem just like what you posted. I've thrown pretty much every conceivable part possible at my car without any improvement in behavior (it has gotten steadily worse over time, albeit slowly).

Sapote, why do you say this is normal for these cars? My previous S54 M3 (2005) never did anything like this, and my current one (2002) didn't for the first 25k miles that I drove it, and then started behaving like this very suddenly one day. Do you really think we're chasing something that doesn't matter? Curious to hear your thoughts!

[TexaZ3]

I don't see anything wrong with that cold start.

[elbert]

I've owned this car for almost 8 years and it never did that, ever so i don't think it's "normal" for these cars, my opinion.

I've had my car since new (so 17 years), and it's been doing this from the beginning. If anything, I was going to say that the video isn't too bad. I've had the car not start on the first try, or stumble until I blip the gas.

[BigLooga]

What i noticed for me is that when it stumbles a bit on cold start, if i give it a very slight 1% gas the rpm stumbles even more but if i give it a good jab, about 25-40% gas then it's normal and revs fine. All this stops as soon as i reverse from my garage, put it into first gear and it's like it was always been.

[BigLooga]

I've had my car since new (so 17 years), and it's been doing this from the beginning. If anything, I was going to say that the video isn't too bad. I've had the car not start on the first try, or stumble until I blip the gas.

Damn, i've never own any vehicle that had that beahviour or any startup unless there was an issue with it. Does your car still stumble like this on cold start? Did it ever crank, stumble and die on a cold start?

[BigLooga]

Interestingly: this behaviour is in some cases similar to my car's rough-start behaviour (see here: https://nam3forum.com/forums/forum/m...ts-please-help), except my problem is actually usually on warm starts rather than cold (might have equal likelihood for both, but I warm-start my car far more often than cold). My rough starts are sometimes rougher, but in milder cases seem just like what you posted. I've thrown pretty much every conceivable part possible at my car without any improvement in behavior (it has gotten steadily worse over time, albeit slowly).

Sapote, why do you say this is normal for these cars? My previous S54 M3 (2005) never did anything like this, and my current one (2002) didn't for the first 25k miles that I drove it, and then started behaving like this very suddenly one day. Do you really think we're chasing something that doesn't matter? Curious to hear your thoughts!

Jesus... i just read your thread ATB88, my issue is very similar, just started about 2 weeks ago. It's been getting colder in my area too but i regularly drove my car at this time of year until October, even November sometimes and never got this. I will follow your thread. Thanks!

[ATB88]

Jesus... i just read your thread ATB88, my issue is very similar, just started about 2 weeks ago. It's been getting colder in my area too but i regularly drove my car at this time of year until October, even November sometimes and never got this. I will follow your thread. Thanks!

Interesting to hear reports from others that their car's always started like this, whereas you and I are used to much more immediate and stable starts. It might be possible that this kind of behaviour is to some degree "within spec" or expectation for these engines even if there is some concrete cause for why our engines didn't do it before but do now.

In my case, though, sometimes it just doesn't start on the first try (but if it fails on first try, always starts right up on second). So I know that in my case, there is definitely some sort of underlying issue somewhere. I guess the question is if it's related to these softer rough starts that some people seem to be experiencing normally. Hope we find out

[AvusM5]

Mine has 73k miles and behaves the same way. I just installed a new fuel pump and filter and it did not make a difference. My understanding is this is normal. The S54 is not your average pedestrian engine

[jbfrancis3]

I think there are a few layers here. Feedback seems to be, yes, many experience similar. Does that mean it came that way from the factory? No. I'd personally want to fix it like the OP.

Don't take my word for it - you can also easily google a cold start video and see that a normal start on this vehicle is what you'd expect.

My simple-minded observations/questions:
- What if you keep the key in the crank position 1/2 sec longer?
- Any modifications to the vehicle, tune or otherwise?
- The starter motor doesn't sound like its cranking 100%, despite your noting a new battery. What's your battery's resting voltage after a day or so?

[AvusM5]

I think there are a few layers here. Feedback seems to be, yes, many experience similar. Does that mean it came that way from the factory? No. I'd personally want to fix it like the OP.

Don't take my word for it - you can also easily google a cold start video and see that a normal start on this vehicle is what you'd expect.

My simple-minded observations/questions:
- What if you keep the key in the crank position 1/2 sec longer?
- Any modifications to the vehicle, tune or otherwise?
- The starter motor doesn't sound like its cranking 100%, despite your noting a new battery. What's your battery's resting voltage after a day or so?

I find this very interesting. From a 2001 review by Car and Driver of the E46 M3. It seems that this was happening with brand new examples back in the day.

[elbert]

Damn, i've never own any vehicle that had that beahviour or any startup unless there was an issue with it. Does your car still stumble like this on cold start? Did it ever crank, stumble and die on a cold start?

Most of the time it starts fine, but I'll still have cold start issues every once in a while.
Sometimes it will crank but not start. When I retry, it will fire right up, smoothly.
Other times, it will start rough, and the rpm will fluctuate. Blipping the gas will smoothen out the revs. I never let it fluctuate too long to see, but once it starts, it won't die.

Does that mean it came that way from the factory? No.

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

[heinzboehmer]

I find this very interesting. From a 2001 review by Car and Driver of the E46 M3. It seems that this was happening with brand new examples back in the day.

Nice find. Pretty definitively proves that this happened when the cars were new too, in my mind.