I posted about this in a new thread under "new software load" but the situtation has changed. The new software is loaded and it still stutters in the AM. The dealer has called me back stating that the stuttering that I experience when it sits overnight is 'normal' due to the M engine, and they don't intend to fix it. I've cold-driven other M3s and never noticed it.

Do any of you experience stuttering in coler climates? it's been int he 50s-60s here at night lately. Is this BS or normal?

By stuttering I mean momentary power drop-offs when holding the throttle steady or accelerating. I can't beleive that with all t he research I've done this has never been mentioned.

I am supposed to pick up the car later today, which is why I put ASAP in the title.

Linky to other thread:
http://bimmerforums.com/forum/showthread.php?t=422805

In the morning, you'll probably experience lumpy idle & hesitation... but at a steady state of cruise it shouldn't hiccup any. If the coolant/oil are cold, the engine is very unhappy and will drive accordingly, however... once warm, it should be fine.

Ah thanks.

Is it supposed to be gone by the time only 3 lights are lit (2 red 1 yeller) on the tach?

Because mine will do it in excess of 10 minutes of running time.

normally by the time the 2 red/1yellow are lit the stumbling and 'odd' performance quirks are gone, but it varies engine to engine.

normally by the time the 2 red/1yellow are lit the stumbling and 'odd' performance quirks are gone, but it varies engine to engine.

So this 'should' be happening if I am driving 60mph on the highway? --If I am on the highway in the first few (10?) minutes?

No... it only happens early in the drive cycle if the car is cold, if you are on hte highway, you should not be experiencing any shudder or loss of power. Once you reach a cruising speed, regardless of engine temperature, power should be consistent and smooth.

Ok thanks. I've been searching around and it seems to be a coil/fuel pressure issue. Do you know if they can monitor the fuel pressure electronically? (i.e. is there a sending unit in the car? that I can read with ODB-II or them with their connection?)

My service rep said without any codes they can do nothing and of course he turned it off. Is trip data stored in volitale memory (that goeas away after the car is off?)

Thanks so much!

fuel pressure and coils could very well be the problem. I think you are supposed to have 5bar of fuel pressure at idle then raise to 5.5bar under load.

you could also have the bad coil issue... there was a recall to replace all 6 coils if any one of them showed earlier signs of failure.

Found the SIB (Faxing it to the dealer. I don't wknow why I shoud have to the detective work):

For those of you that use search, here is the link:
http://www.thatsoundsagoodidea.com/bmw/bmw_e46_m3_bulletins_120204.pdf
Here is the page with other SIBs:
http://www.thatsoundsagoodidea.com/bmw/index.html

I looked into the cold-start idle issue / software fix- it does not look like my problem.

Kevlar wouldnt it go into full limp mode? I am wondering if he is experiencing what I just had. I was having a hiccup while accelerating. Then it just died and it turned out that my MAF sensor was bad and somehow my just newly installed vanos unit from 2 months before turned out to be jamming so it was one of the two that killed it.

It depends on how badly the coil(s) were malfunctioning... it won't always trigger a limp mode or even a check engine scenario.

The scenario you mentioned could also be the cause...

Yeah because I remember when mine went out it didnt go nuts till after I drove for a bit.

Well the dealer is giving me problems for it. I went in there with the SIB and told them that is what I wanted to have done. They pushed back saying "if there is no SES light ... and no codes ... "

Tomorrow I am meeting them bright an early for a morning drive.

I want the coils replaced, and the fuel pump if the coils don't fix it.

They don't even have to pay - its under a 3rd party extended warrenty! :mad:

When they give you a hard time, tell them that when the vehicle stalls or surges in traffic and you get into an accident, you are going to hold them responsible. (not that that story will work, but it's worth a try).

You can tell them that a lack of codes and a lack of a cE light doesn't mean there is a lack of a problem... it just means that the computer hasn't figured it out yet.

You can tell them that a lack of codes and a lack of a cE light doesn't mean there is a lack of a problem... it just means that the computer hasn't figured it out yet.

Thats exactly what I said, but then they said oh, "but the M3 is really good about reporting it."

This is about 2 minutes after they got done telling me about how they are buying GM ECU technology to put in BMW computers.

How many miles have you put on the car since you started having the problems?

I would take it on the highway and just cruise for about 40 miles and see if that cleans it up if not then you may have a bad MAF sensor because thats exactly what my car did then it died. If you can pull out the MAF sensor and see if there is oil on there. If there is then the person had an intake on it and maybe he got oil on it and its making it spaz.

zero - the morning after I drove it home fom buying it the SES light came on and itgot the MAF replaced. It's been about 1.5 tanks of gas. The computer has about 50 miles on it since beng reprogrammed.

EDIT: Update after morning drive with dealer:
They describe it as a 'hole' at 5k, even though it is intermittent. I had only 1 good acceleration run from stop to about near readline for the 7 miles that I drive it. It smoothed out from a jerk to a hole after temps got above the 1st dot. While below the dot the whole RPM range was affected. It is now confirmed and they are putting a different mechanic on it. It's not everytime at 5k, but each time we noticed it and 5k was the most common point.

EDIT2: After thought:
*I* now suspect the fuel pump. I think it has to deal with it responding to the drop in pressure from fueling the acceleration - that it can't keep up with demand. As soon as I go WOT pressure drops. it comes on, but can't build the pressure up in time. It doesn't quite explain my cruising issue, but I venture to say it's probably related.

The computer is good sometimes about reporting problems... but look at my problem where my cats failed. The ECU didn't report a damn thing.

Anyway... if you suspect that fuel pressure is a problem, they should be able to monitor it to ensure that you have 5bar at idle and 5.5bar under load. It should be able to maintain that 5.5bar with zero problems.

From what your are describing, it could be the VANOS unit. If the oil pump connected to the VANOS unit is not building pressure properly (the VANOS unit needs about 100bar of pressure to work correctly), it could explain the entire affected RPM range. When the car is shutoff, the VANOS goes to completely retarded to allow for easy starting but after pressure builds, it is supposed to adjust. If it doesn't adjust that may explain the rough running.

That's just a thought tho.

Dumb idea but did you check the fuel pressure regulator and it's vacuum line?

No, its up to them to do that.

I want to thank everyone for their help! I am coming from a situation where I know all about the 4g63 and 4g64 mitsu S/DOHC engines to a real engine with VANOS. Its quite humbling not knowing swat!!

Update: Dealer is trying a new (even though it was just replaced) MAF.

This sounds exactly like what happened with me. When they replaced the MAF and the vanos it went away. Let me guess the stutter is most apparent in 3rd if I am correct

This sounds exactly like what happened with me. When they replaced the MAF and the vanos it went away. Let me guess the stutter is most apparent in 3rd if I am correct

I don't remember the gear. I shift without thining about where the stick is going, and I am too busy watching the tach.

That combination makes no sense - the vanos adjust per RPM. the MAF only feeds CFM (one way or another) to the ECU. The ECU calcs the injector pulse timings. (Which then affect RPM) But the VANOS as I understand it are all mechanical/hydrolic.

The only time I've felt anything like this is when you hit fuel-cut in turbo cars to keep from running lean, but my power comes back right away.

(With those comments above I am fishing for a better understanding of the S54 engine :help )

Thanks again guys!

The VANOS unit is operated by the ECU depending upon a huge variety of factors, one of them I do believe is gear dependent (ground speed vs RPM). The units operate on oil pressure upwards of 100bar (not psi).

Yeah my power would hiccup and it would only happen for about a second but right before it died it would happen for about 2 seconds

Ok so here's the deal. The M3 used two fuel pressures. There is a relay and a control module which governs which pressure is used. Some part of that system was intermittently failing, causing it to switch to low pressure instead of staying at high pressure. The dealer replaced the two components (at BMW USA's expense, I don't know why...) and now it works beatifully!