I've been reading about this yo-yo....stumble.... issue since the beginning of time... it seems.
It's truly a horrible situation and I feel for all those miniacs who have been and continue to be..... subjected to this ...horror!!!!!!!!!!!!!

I have a 2002... May 02 build..... MCS
I've only upgraded the software once.... so my best guess is that I'm running 3.2
If I recall it was the 1st iteration to address the cold-start issue.
I have the Helix pulley, Webb/Powerchip (based on my 3.2 software) ECU re-map , Borla Street Exhaust and Maddness Air-intake.
(As a side note every time I visit my dealer I announce to every person at the dealership .." DO NOT TOUCH MY ECU". It has become a bit of a joke ...but in has saved my car from many problems...it seems).

My MCS fortunately.... has never experienced the yo-yo and/or stumble.

Here's my point/question.

Simply stated ...WHY????
(Why what..... you may be thinking?)

Why is one car effected.... and the car next to it...with the exact same software is NOT?
I've read posts stating that that the 3.6 upgrade has cured the issues and posts stating that it has not.
It seems IMHO.... that we should all have this problem or none of us should have this problem.
I honestly don't get it????

I assure you that if my MCS had this issue it would be...gone... sold... traded-in....finished!!!!
I truly feel for those who are affected by this...respect your drive and commitment... and hope that eventually ...BMW... fesses up to this and provides a.... TRUE GLOBAL FIX !!!!!!

I just don't understand how it's so...random!!!!!


Peace,
D



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I own a 2002 MCS w/ alot of stuff on it.

 

MC 5/02 build here also. No stumble or yo-yo. I wonder if this might be a parts problem since car manufacturers are known to get bids from different jobbers (for the same part) over the life of the production cycle of a car. This might explain why some MCS have the stumble/yo-yo problem and why others don't.

Ryephile, great observation and good testing. Your input is most helpful. And yes, maybe the MINI service techs know even less than you.

 

Update from dealership, and a shocking twist!

I stopped by my dealership and gave my Service Advisor a ride in my car. I simply told him "look at the boost gauge, and listen to the intake, it's really obvious". As I pull out of the parking lot at medium throttle on-boost, he's like "woah, that's strange" as the boost gauge displays the boost-resonance (yo-yo). Obviously he didn't have a clue what it could be, so I shared my research and findings to date. The only advice he could offer is to "give the technician a ride too". Wonderful :evil:

My buddy Christian (4GAZM) called me and said the engine in his '02 MCS was acting strange. I told him to come over and we'll go out for a spin. Well, after 50,800 miles, his MCS has just now developed the Yo-yo! The background is: I've driven his MCS many many times, and I've always loved how perfect the engine feels (he has original software, I think it's 31). His only mod was a Madness intake. Last weekend he was part of my Pulley Party, and picked up the pulley and switched to the ALTA intake. The only electrical change was that, during the pulley install, the ECU has to be unplugged and removed from the car. Now I'm baffled! An ECU reset obviously does not change core algorithms, however it will erase adaptive logic memory. So, last night, I did another ECU reset, and then we took it for another drive. Pull out of the driveway, and NO yo-yo though all the gears. I brake and go through the gears again - uh oh, just a touch of yo-yo. Stop and go through the gears again and again and again, each time the yo-yo gets worse and worse until it's almost as bad as my '04 MCS! WTF? The only cause for it to get progressively worse is the Adaptive Logic learning to screw up, possibly from a bad/flaky sensor. Check out this time table with both mine and Christian's MINI's:

Ryan's '04 MCS -
Day one - yo-yo, gets progressively worse over time
Week two - install boost gauge, now the yo-yo is visible
yo-yo gradually tapers in amplitude, weather is relatively stable
Week six - pulley, ECU re-map, and intake - yo-yo now huge
Week seven - yo-yo tapers in amplitude again
Now - reset ECU, immediate yo-yo, then it tapers off slightly. Cause is most likely bad sensor and/or bad core algorithms

Christian's '02 MCS -
Day one - perfect engine
cold start problems in winter, common with this software revision
Month 12 - Madness intake installed, more power/music
Month 15 - Pulley, and switch to ALTA intake, still perfect
Month 15.3 - yo-yo develops one week after pulley install
Month 15.4 - Ryan does ECU reset, determines adaptive logic and/or bad sensor to blame

Ok, compare the two, in both cases the possibility of bad sensors are prevalent. Also, in both cases, you can see the adaptive logic is either helping or hurting the situation (helping mine, hurting Christians). My question is WHY THE HELL?! Next I want to get a hold of Chad123's '03 MCS that has both the stumble and a slight yo-yo, and see how the ECU reset affects it. Now I really have to dust off my ‘Scope!

Conclusions
My gut still tells me it’s either the MAP sensor or the logic controlling the servo in the throttle body that is causing the problems. Its just speculation at this point. If I feel adventurous, I may just go buy another MAP sensor and/or throttle body and see if anything changes. Since Christian’s MINI has over 50k miles on it, I can see how a sensor would go bad. It makes NO sense for the ECU to just now throw a fit and start yo-yoing. I’m almost positive it’s not the ECU’s fault for the yo-yo, however the ECU does play an integral part in what’s going on.

More updates as I get ‘em,
Ryan

 

Ryephile... just to clarify, you're hypothesizing that a faulty sensor is responsible for the yo-yo solely? What about the stumble? Do you think that's computer related? Is that why the latest software update fixes the stumble but doesn't take care of the yo-yo? Do you think the two are related in anyway, or does the sensor theory mean that they're unrelated?

I'll stop pestering now

 

Whooaaa...now I have another reason to keep mine out Motor City's hands

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Hi all,

I haven't been here for over a month or so and haven't searched previous post much but is the so call "fix" available yet and if so what prognosis do you have on it. I was call in by a fellow mini goer about a month ago for a special fix installation by my dealer but from my experience it is still there. If nothing, I know for sure that the hesitation at 2000 rpm in 2nd gear during deceleration is definitely there. Also, what about people who is using lawyers on this issue? Please update me.


Thanks
Peter

 

I have an early "non spec" 02 MCS, I have taken it in 3 times for updated software and I still have the problem of the pulsating problem. I hate it, but have basicaly given into the thought of, that is the way it is, my dealerships service department is less than helpful.

 

--->Toastie: It seems to me the Stumble and Yo-Yo are two completely seperate issues. My '03 MCS had only the stumble, and my '04 MCS has only the yo-yo - go figure I think that the yo-yo is the result of the ECU correctly reacting to bad sensor input, but keep in mind it's just speculation.

 

I'm about done with this; the ECU's don't log any codes for the sensors being bad, which means if they sensors are providing bad data - they're operating correctly - and not within the MINI spec, or they're in the process of going bad, sheesh. Basically the ECU's adaptive logic is working correctly, whether that's good or not is another question.

I'm dropping my car off at MCM tomorrow. I've given them strict instructions to exactly follow the MINI Diagnostic guidelines, confirm they lack competence, and forward the issue to MINI USA. The WAIT begins - oh I just can't wait to aquire a nice complimentary rental car

My guess is my MINI will either A) get V36 loaded onto it, and the yo-yo will prevail and MCM will lose CSI points, or B) MINI USA denies the existence of any problem, and throws my modifications in my face and claims it's not their problem. If this happens, I'll scour a junkyard and buy an '02 ECU and BCM and make 'em work in my car

Motor-on...kinda,
Ryan