[StateVector]

Originally Posted by ZM2

We did all six injectors ($575): https://www.fcpeuro.com/products/bmw...-13647639994kt

Anytime I've played the which plug, coil, (and now injector) to replace game, the labor ends up being more if you don't get it right the first time.

And, my car has 40k miles, lots of track days, and years of running ethanol (also installed Bend's fuel filter), so probably better just to replace them all anyways.

Maybe a little painful the first time cost wise to do them all at once, but now that I'm in the FCP replacement cycle on those parts, we just replace them all at each time to completely rule out plug, coil, and now injector issues.

This is really helpful, and thanks for link! I will probably end up buying that kit..last question if you don't mind...is there a complicated calibration process for the injectors that your mechanic had to go through before installation?

[ZM2]

Originally Posted by StateVector

This is really helpful, and thanks for link! I will probably end up buying that kit..last question if you don't mind...is there a complicated calibration process for the injectors that your mechanic had to go through before installation?

No calibration process with the EU6 injectors, just typical injector replacement job.

Some guys upgrade to the EU5 injectors, but that's not necessary unless you're pushing a good bit over 500whp while using E85. And, requires custom tuning or applying the BM3 checkbox.

I'm at 480whp on E50 and don't plan on pushing more, so I just went back with the EU6 injectors.

[StateVector]

Originally Posted by ZM2

No calibration process, just typical injector replacement job.

Awesome, thanks again...I think I'm going to give this a try.

[ctt300]

From what I’ve seen with my car, it has always been one or more ignition coils slowly going bad that finally failed completely with a misfire code for the cylinder with the dead coil. You usually get a lean code and then the above happens down the road. I’ve even had brand new coils fail.

I seriously doubt it’s clogged or failing injectors unless you don’t use top tier fuel. My car is nearing 100K miles and runs like a top with a glass smooth idle. It’s worth running some Techron concentrate every 5k miles or so as well and can alternate with Berryman B12 Chemtool in the tank. If you are running an ethanol blend, then run 3 ounces of TCW3 2 cycle oil in the gas to restore some lubricity to the ethanol blend and it also has detergents in it that keep the entire fuel system clean. A bit of preventative maintenance goes a long way as does running the car hard to clear out carbon deposits, but don’t think most here would have that problem…lol.

[StateVector]

Originally Posted by ctt300

From what I’ve seen with my car, it has always been one or more ignition coils slowly going bad that finally failed completely with a misfire code for the cylinder with the dead coil. You usually get a lean code and then the above happens down the road. I’ve even had brand new coils fail.

I seriously doubt it’s clogged or failing injectors unless you don’t use top tier fuel. My car is nearing 100K miles and runs like a top with a glass smooth idle. It’s worth running some Techron concentrate every 5k miles or so as well and can alternate with Berryman B12 Chemtool in the tank. If you are running an ethanol blend, then run 3 ounces of TCW3 2 cycle oil in the gas to restore some lubricity to the ethanol blend and it also has detergents in it that keep the entire fuel system clean. A bit of preventative maintenance goes a long way as does running the car hard to clear out carbon deposits, but don’t think most here would have that problem…lol.

Let me try to understand your timeline here from your past experience:

1) You started seeing the cold start stumble and rev up once at first start up of the day
2) Then this happened at every start up
3) Then eventually get a lean code and/or misfire code
4) Then you replace coils and the startup idle dip rev-up goes away entirely?

I have seen multiple reports that leaky injectors cause this weird startup behavior, and it sort of makes sense when you think about it. It only happens after the car has been sitting for about 24 hours. Every startup after that is perfectly normal, along with every idle situation, as long as it's within the 24 hours of initial start (not enough fuel has leaked yet to cause the strange cold start dip and rev up). This is my situation right now as it was for the others and will probably turn into every start eventually.

[ZM2]

For my full update, see my latest post on this thread: https://f87.bimmerpost.com/forums/sh....php?t=1884838

Direct post link: https://f87.bimmerpost.com/forums/sh...6&postcount=70

[StateVector]

Originally Posted by ZM2

We did all six injectors ($575): https://www.fcpeuro.com/products/bmw...-13647639994kt

Anytime I've played the which plug, coil, (and now injector) to replace game, the labor ends up being more if you don't get it right the first time.

And, my car has 40k miles, lots of track days, and years of running ethanol (also installed Bend's fuel filter), so probably better just to replace them all anyways.

Maybe a little more painful the first-time cost wise to do them all at once, but now that I'm in the FCP replacement cycle for those parts, we just replace them all each time to completely rule out plug, coil, and now injector issues.

Thank you ZM2 for all the advice. A quick update on my M2 is that I had the shop replace all six injectors with new EU6 injectors from the link above. BOOM! The cold start dip problem is fixed and now it starts up like a normal car. While it's not a cheap fix, the leaky injector syndrome definitely seems to be the root cause of this cold start dip stumble/stall that seems to be fairly common.

[shaneguags]

Originally Posted by StateVector

Thank you ZM2 for all the advice. A quick update on my M2 is that I had the shop replace all six injectors with new EU6 injectors from the link above. BOOM! The cold start dip problem is fixed and now it starts up like a normal car. While it's not a cheap fix, the leaky injector syndrome definitely seems to be the root cause of this cold start dip stumble/stall that seems to be fairly common.

I had the same issue as well. my car had two leaky injectors and that fixed my issue

[StateVector]

Originally Posted by shaneguags

I had the same issue as well. my car had two leaky injectors and that fixed my issue

So the new injectors fixed the issue of the car stumbling on cold start and about to stall, but does this cold start still look "normal" to you guys? All the M2 cold start videos I can find, the RPMs shoot up immediately and then drop...on my car, the car starts as you can see, has about a 4 second delay, sort of realizes "oh this is a cold start" and then jumps to about 2k rpm and gradually declines from there and drops under 1k in about 30 seconds. Again, every start from that point on during the day is normal all around. What do you think?

[shaneguags]

Originally Posted by StateVector

So the new injectors fixed the issue of the car stumbling on cold start and about to stall, but does this cold start still look "normal" to you guys? All the M2 cold start videos I can find, the RPMs shoot up immediately and then drop...on my car, the car starts as you can see, has about a 4 second delay, sort of realizes "oh this is a cold start" and then jumps to about 2k rpm and gradually declines from there and drops under 1k in about 30 seconds. Again, every start from that point on during the day is normal all around. What do you think?

are you on ethanol ?

[StateVector]

Originally Posted by shaneguags

are you on ethanol ?

No, just 91.

[shaneguags]

Originally Posted by StateVector

No, just 91.

you changed your spark plugs recently ?

[StateVector]

Originally Posted by shaneguags

you changed your spark plugs recently ?

Spark plugs changed 8 months ago.

[shaneguags]

Originally Posted by StateVector

Spark plugs changed 8 months ago.

weird, coincidentally, my car did the same thing. it had a hiccup on the cold start. I have new injectors and new spark plugs. let me know if you can watch this video I just took : https://share.icloud.com/photos/006p...RbbQXhUPH4p8pw

[shaneguags]

Just logged a cold start :

https://www.bootmod3.net/log?id=633a...0b43298cbc23f7

I wasn't completely cold but it was sitting for around 5 hours. startup felt fine.

[StateVector]

Originally Posted by shaneguags

Just logged a cold start :

https://www.bootmod3.net/log?id=633a...0b43298cbc23f7

I wasn't completely cold but it was sitting for around 5 hours. startup felt fine.

yeah, that cold start video is similar to mine...although my delay is much longer being around 4 seconds before it blips itself up to 2k. Maybe this is just baked into the cold start programming? I just don't see many exactly like mine so I'm not sure if it's typical.

Regarding your log after 5 hours, anything you see that is interesting? Even if my car sits for 12 hours it seems to be just a normal start. For some reason, it's after around 24hours sitting, even with new injectors, it likes to take a few seconds after start at 1k rpm and then rev up to 2k rpm and drop from there. Who knows.

[shaneguags]

Originally Posted by StateVector

yeah, that cold start video is similar to mine...although my delay is much longer being around 4 seconds before it blips itself up to 2k. Maybe this is just baked into the cold start programming? I just don't see many exactly like mine so I'm not sure if it's typical.

Regarding your log after 5 hours, anything you see that is interesting? Even if my car sits for 12 hours it seems to be just a normal start. For some reason, it's after around 24hours sitting, even with new injectors, it likes to take a few seconds after start at 1k rpm and then rev up to 2k rpm and drop from there. Who knows.

well for me it was weird because I first cold started my car in 6 days and it was completely smooth with no hiccups. I did a little drive, came back, and did another cold start later it hiccuped.

[StateVector]

Originally Posted by shaneguags

well for me it was weird because I first cold started my car in 6 days and it was completely smooth with no hiccups. I did a little drive, came back, and did another cold start later it hiccuped.

Interesting.

[///393]

I’ve got 20k miles on mine and it never sees more than 1100RPM upon cold start. I run Shell 93 and I’m on NGKs gapped to .23 running BM3 S2(will be going back to stock plugs at some point.)

Generally it behaves the same on a cold start after 3 days as it does after 8 hours. I’ll get a video of it for reference later this week.

[shaneguags]

it could be because my gap size is .018 but I did that for my E60 blend. I'm on full 93 as of now, maybe that's the issue ?

[KevinC]

Using Top Tier gas or some shitty generic stuff?

[StateVector]

Originally Posted by KevinC

Using Top Tier gas or some shitty generic stuff?

I only use organic, grass-fed gas. After talking with my BMW tech today, who is very familiar with N55s, and the one who installed my injectors, told me that the few second delay before rev-up is what he sees all the time at altitude (we're at about 6k ft in Colorado Springs); apparently, nothing to worry about.