Sorry if this is old news, but I am reading references to a "stumble" and wondering what you all are referring to. I am the happy owner of a 2004 MCS, Sport/Premium, and have noticed that the car (not the engine, which seems smooth, but as if it's getting a glitch in receiving gas) sometimes hiccups. I can't tell if it's me lightening my foot on the gas...it never happens when I am accelerating, or when I am coasting, but only seems to happen when changing load...and it seems to happen around 3000 RPM. Is that the stumble?? Or is this just the way the Cooper S drives, with the electronic throttle? I have had the car a couple of weeks and wonder if it is happening more or if it my imagination..

It also idled a bit roughly when I first started this morning, but cleared right up. I read in some of the threads in the "under the bonnet" area that others have experienced this as well, but that these things are not the stumble. So what is the stumble? And is my car driving incorrectly or is this normal for Cooper S?

Any help would be appreciated..I am very sensitive to the way a car handles (hence I love sports cars) and want to be sure I know how my baby feels best...

Addition: I realize now that what I may have is the yo-yo described in the chronicles..is this something I need to take to the dealer? It is so sporadic (at least right now) and just having a heavier foot seems to solve it...

As for the stumble, sometimes, the car doesn't seem to notice when I am starting from a standstill. It only happens at a standstill. Then it takes off. Is that the stumble??

 

Sounds like you have the yo-yo. By the end of this month, v.38 of the ECU software should be at your dealer. This update greatly lessens the yo-yo and transforms your cruise control into a thing of beauty! However, as you have read in The Yo-Yo Chronicles, there are some trade-offs in going the v.38 route.

It also sounds like you may have the stumble/bog symptom when first starting off. The v.36 update has taken care of both these issues in almost all cases. I'm guessing that your 04 MCS may have entered the US in mid/late September of 03. which could have been before the VPC in NJ was reprogramming all incoming 04s with v.36. Let us know if that timing sounds about right.

In any case, if you don't want to go the v.38 route, you should have your dealer make sure you are at least at the v.36 level. This is a free update.

Theo

 

Thanks! My car's date is 05/04, so I would think it is a v36...do I just go to the dealer and ask for the update? Do I have to describe everything? I sure hope the mini dealer has good service people that know what they are doing... that worries me. It does sound like there is a trade-off with the v38...

 

With an 05/04 production date, you must certainly have v.36. Thus, the stumble/bog issue is puzzling. How often does this happen?

I can get my MCS to bog if I try to start off with the rpms too low (say ~1000 rpms or so). If I keep the rpms at about 1200, it's a smooth take-off every time.

Another thought might be to reset the ECU and have it go through the adaptation period again. I did this accidently one time and I liked the result! Just disconnect the positive terminal of the battery for a few minutes. You'll lose the trip odo info and the avg mpg/mph info but I think the radio settings remain unchanged.

Theo

 

I think it may be me starting it at rpms too low...I am trying to slow my release of the clutch out of the standstill so that the rpms can get up there..when I do that it doesn't sit there like it's asleep and then wakes up suddenly You said you can get it to stumble when you start it at 1000, so I will try slowing my clutch action a little and see if that helps. I am so conscious of the clutch and not wanting to put too much on it, I tend to avoid using it as much as possible, including sometimes letting it out too fast.


As for the yo-yo, it is intermittent, very hard for me to tell because the car is still new to me, but it sure sounds like what is described.

What does removing the adaptation do? Is that getting the car to forget my tendencies? I have the S..if I were to do that, would I disconnect the terminal under the bonnet, where we apply jump starts, or back in the boot, at the actual battery? I suspect that under the bonnet would suffice, but I want to be as accurate as possible...

You are the best for your help. I love these forums, it so awesome to find other people that are as nuts about their cars as I am!

 

Basically, the ECU adjusts it's "maps" (the data that it uses for certain operational parameters) based on the driving "style" of the operator. This is done to try to adapt the drivability to match the driver.

In this case, I wouldn't be so tender with the clutch. My driving style, while not that of a racer, is spirited enough to have given the clutch quite a workout with no ill effects. Keep the rpms up a little more and let the clutch out a little more slowly. As you get used to the relationship of the throttle/clutch thing, you will be rewarded with one of the nicest setups for a car in our class. The MCS is very forgiving!

By disconnecting the power from the ECU we are doing exactly as you have deduced: it will start over to learn your driving habits. If you modify your throttle/clutch approach during this process, you may find that the bog you have been experiencing will be greatly reduced if not eliminated.

When I disconnected mine, it was in the boot. I have not tried a disconnect under the bonnet but, if possible, that would work as well. There is also an ECU reset that can be done via the ignition and trip odo button, but the battery disconnect might be more straightforward.

Let us know how you make out...

Theo

 

>I think it may be me starting it at rpms too low...I am trying to slow my release of the clutch out of the standstill so that the rpms can get up there..when I do that it doesn't sit there like it's asleep and then wakes up suddenly


jennscooper- I have pre-v36 software and did not get the v36+ version
last week during my first oil change at the dealer because there are
people with v36 that have the stumble comeback.

I get 2 symptoms from my per-v36 software... this is just for your reference.

1. Cold hiccup- car hiccups at first full clutch engagement when I pull out in 1st gear regardless of how gently I engage the clutch. What I do is slip
1st gear to get the car moving, but do not engage the clutch fully...then
slip 2nd gear while I pull above 10mph and engage fully. The car hiccup is
so minimal that it goes unnoticed inside the cabin. The clutch is heated,
but not burnt or anything like that...not enough to prematurely wear out
the clutch.

2. Hiccup- Even after my car is fully warmed up the car will hiccup if I rev
too high (2500-3000rpm) and slip too long (more than 3 sec) before
the clutch is fully engaged in 1st. It is an abrupt hiccup, but not the
huge stumble (fuel cut off) some times felt on other MCS. The remedy
for this is to keep RPM around 2k or lower and engage smoothly within
3sec from a standstill for normal acceleration. If I need to launch the
car from a standstill, the car will not hiccup as long as my rev is over
3500rpm and either slip clutch or drop the clutch a little higher for
some wheel spin.

I use to occassionally get 2nd gear hiccups during a spirited run through a
corner, but with the UNIchip, that area has been completely taken out.

 

While I have a Cooper, I always rev the engine to about 3,500 before letting out the clutch--and do subsequent shifts at 4,500 or 5,000. Anytime I let the clutch out below 2,000, especially 1,500 or less, it's like running in molasass. Granted your MCS has 50 more hp than mine, but that doesn't make much of a difference at the low end. The Stumble is an awful chop of the throttle feeling during hard acceleration. I feel it all the time in 1st gear--I take off, and accelerate hard--flooring it, and the gas will stop for a second, then re-engage--causing the car to jerk. Almost like you let out the clutch too fast--except this time, my foot is only on the gas, not the clutch, and it happens AFTER the shift--not during or shortly afterwards.

I've also got V.36, and will hopefully be getting V.38 when I go in for my next Service #2 in a few thousand miles.

 

I have a Feb 04 MCS. I presume that makes it V36. It took me a while to recognize the Stumble and Yo-Yo. I presume others have it much worse than what I have experienced. I do have the inaccurate cruise control that seems to fluctuate within about a 5-10km speed range.

Here are my descriptions of the Stumble and Yo-Yo:

Stumble: pulling away from a stop the engine bogs down and hesitates. I thought at first it was driving technique (poor) but it is consistent and only abscent when I increase the rpm to 2,000. It finally occured to me that this is the infamous stumble! - Not a big deal on my car.

Yo-Yo: Around 3,000 RPM in any gear either accelreating or cruising there is an spot where the engine "flutters". By this I mean simply an somewhat uneven power delivery. Again not a huge deal but a bigger deal than the stumble. At this point I've put it down as part of the car's character, but also figured it is a very mild case of the Yo-Yo.

I am just reaching the end of my 2,000km break in period. Overall the car has worked very well.