I'm sure it's been dicussed, but I can't find the topic in any searches I've done. Please help by pointing me in the right direction?

My Nov delivery '04 S has an extremely annoying occillatory surge during moderate acceleration...not felt during very gentle accels or harder ones. It takes over at approx 2500-3500 rpm and feels like I'm repeatedly flooring it then letting off.

Dealer: "they just do that"

Me: "nonsense"

Anyone?

P.S. I don't think that this is the famed "stumble" issue as this does not occur during clutch take-up and is not limited to accels from a dead stop?

P.P.S. THE V36 IS INSTALLED NOW (a few days later) AND YO-YO IS 90% GONE. MANY THANKS TO THOSE WHO'VE BROUGHT THIS ISSUE TO BMW's ATTENTION B4 ME, THE REST OF US OWE YOU BIG-TIME!!! THANKYOU, THANKYOU, THANKYOU!!!

 

Believe me, they don't "just do that." Throttle problem?

 

Welcome to NAM Ray,

what you describe is the dreaded Yo-Yo. Do a search, there is much ranting and no raving 'bout it. MINI may have a fix in V36 software, then again maybe not. You may have a long wait.

 

Sounds like you have the surge problem. There are definitely threads about this. Check the search function for stumble.

 

Yeah sounds like you got the "yo-yo". I have a Sept. build 2004 MCS, and have it too. It seems to have gotten better since I have broken it in, but it is still there, just not as pronounced as before. I don't think there is much you can do about it right now. I'm not sure if the ECU upgrades will help to get rid of it.

Cheers

 

Dealer: "they just do that"

That is actually true if you were one of the ones lucky enough to buy a yoyo car.

BMW have been trying to sweep us all under the rug and hope we go away for the best part of a year now.



_________________
'03 S DS

 

Yep! You got "yo-yo" My Sept. build 04 mcs didn't start yo-yoing until about 500 miles. At 2500 miles still doing it. I'm not sure the v36 ECU up-grade even addresses the yo-yo problem as it is more to help solve the "stumble" that, thankfully I don't have.

 

From all that I've heard, 36 makes the car run better, generally, but does nothing specific to address the yo yo (which, by the way, it seems you have--charming, no?). Read any of the stumble threads--they're cousins--and bask in the understanding that you are not alone.

MINI/BMWAG also attempted to sweep the stumblers under the rug but they've (Apparently. Hopefully) addressed that issue. Perhaps Yo yo is on their honey do list...

 

Seems like most '04 MCS folks (including me!) have the yo-yo but (thankfully) not the stumble. We are just hearing of V.36 software upgrades coming on line for dealers to update customers' cars. It shouldn't be too long before an adventurous '04 MCS owner gets updated with v.36 and we find out about the yo-yo.

Volunteers??

Theo

 

My car has the yo-yo specifically from 3k-3.5k RPM's, most prevalent in 2nd gear and next in 3rd gear. If you are flooring it, it won't happen, if you are going light on acceleration it won't happen, somewhere in between is key. I don't believe my car did this when it was stock. It's kind of annoying but it never really gets to me, especially because my last forced induction car had the same EXACT issue (1.8t). Blahness, but then again.. lots more happiness covers this blahness! Especially with all the posts reading "December 1." Yay! Christmas is coming! :smile: Good night all

 

I have a Sept built 04 MCS. After installing an Alta-intake, I can actually hear the intake noise pulsing in 2nd thorugh 6th gear. It is easily felt in 2nd and 3rd, but in higher gears I think the gearing is too high for the yo-yo effect to be felt. However I can definitely still hear it in the intake noise. I'm waiting for others to report back regarding whether V36 fixes this yo-yo.

 

ok, here's the latest on my problem....

V36 installed, yo-yo 90% gone. Yessssssssssssss. Others reporting same results.
I'll re-post if the fix comes unglued.

In the mean-time, everyone please go get V36 installed and I suspect you'll be much happier.

Many, many thanks to all those who've gone b4 me and made BMW solve this issue. The rest of us are standing upon your shoulders!!!!!!!!!!!!

 

I spoke with my dealer yesterday. He said they have a German v36. They are going to try it Monday on an MCS. German? I am going in for service Tuesday. I don't think that is enough time for me to learn German...

 

>>
>>
>>ok, here's the latest on my problem....
>>
>>V36 installed, yo-yo 90% gone. Yessssssssssssss. Others reporting same results.
>>I'll re-post if the fix comes unglued.
>>
>> {snip}

ray --

What do you describe as "90%" gone? When do you still feel the yo-yo? During which driving situations have you noticed its absence? Sorry...but my brain seems to be affected by the current Nor'easter!

Thanks a bunch,

Theo
Hills of Western MA

 

is/was during medium throttle between approx2500-4000rpm, gears 1-3. was much harsher b4 v36 upgrade. Now barely noticable.........

 

>>is/was during medium throttle between approx2500-4000rpm, gears 1-3. was much harsher b4 v36 upgrade. Now barely noticable.........

That sounds positive. I guess a good test is how will your MINI do once the weather warms up because we know that the colder weather is helpful to minimize the problem. Good luck.

 

My 10/03 build MCS does the exact same thing ray described. It is moderate throttle, actually positive boost only, and with my boost gauge I can actually see the boost wavering. Gear is irrelevant. If you hold the throttle position, it will go away as RPM gets higher and engine load reduces. If you progressively increase throttle position, it will quickly "get through" the wavering and smoothly accelerate. The yo-yo or wavering seems to be consistent with a very narrow band of engine loading.

For clarification, the engine yo-yoed before and after my boost gauge install. This weekend I installed the Webb/Powerchips ECU, which changes all the ECU maps, but not the algorithms, and the yo-yo is still there. Like KatanaPilot said, with an intake, the yo-yo is now more audible, making it annoying to drive. My gut feeling says this is an ECU algorithm problem. If V.36 helps "90%", than they re-wrote the algorithm almost correctly. I feel confident it is not a hardware issue, since the engine performs flawlessly in all other conditions (i.e. light load and WOT). An interesting anomaly is the yo-yo seems to be engine temperature related; it is more prominent when the engine is cold. This may be due to the warm-up maps reacting poorly with the algorithm(s).

Motor-on, partially,
Ryan

 

Software version 36 installed - YOYO still present - now I wonder if that BOG is still there? - maybe I'll find out when I get rear ended pulling into traffic when I least expect it.

 

Trippy brought up a good point over on Roadfly, the yo-yo could be a potentially faulty supercharger bypass-valve. I'm heading to my dealership next Tuesday for a look-see. Hopefully I'll have useful news. I may also poke around under the bonnet this weekend if I'm feeling adventurous

 

I have that yo-yo problem also. Although I just had the pulley and powerchip/ecu changed and it does not show up as often. When it does show up it is more rapid, and shorter in duration. Since the dealer is 4 hours away I will just keep reading up on the posts.

 

>>Trippy brought up a good point over on Roadfly, the yo-yo could be a potentially faulty supercharger bypass-valve. I'm heading to my dealership next Tuesday for a look-see. Hopefully I'll have useful news. I may also poke around under the bonnet this weekend if I'm feeling adventurous

I offered this scenario to the grease monkeys at NJ - they told me not so. Interesting how yoyo starts right at 2800 rpm - then bypass should be closed. I guess they still haven't got the software to handle the transition at partial throttle - doesn't know which way to go.

 

Ryephile,
Thanks again for the party, and staying late so I could change my mind, again.
My yoyo had gone away a few months ago, about 3,300 miles or so. With the pulley installed it's back with a vengance, possibly because I am looking for it more, winter fuel or the cold temps. The shark (which I am hoping to read Randy's review of shortly) has been reported to eliminate this, completely.

Anyway, just wanted to say thanks again, hopefully Mini will find out what causes this, although it was reported in another thread a while back that they haven't even begun trying to solve it, yet.

 

well, what's frustrating is my '03 MCS didn't have this problem at all, and my '04 does! Add another notch for MINI evolving backwards

 

ok, talked to one of my engine-management guru co-workers today:

In it's simplest form, the yo-yo (for me) is due to the throttle body occilating positions during "somewhere in the middle" throttle position. There are a few reasons this happens (since the throttle body is drive-by-wire):
A) the ECU is reacting correctly to bad sensor input (like a faulty MAP sensor)
B) the ECU has adapted via adaptive logic/algorithms correctly to corrupted or bad data
C) the ECU adaptive logic/algorithms are crap and don't work correctly

Now, there is an easy way to rule out the inapplicable possibilities. First off, we have can measure the output of the MAP sensor. If it's output is not smooth (more like a square wave) it is most likely operating outside its' specified parameters (aka it's junk). Second, we can reset the ECU via the speedometer diagnostic (aka disconnecting the battery). If the yo-yo comes back over time, we know it's the adaptive logic/algorithms that are junk. If the yo-yo is immediate after reset, then it's hardware.

Well, since I didn't have a scope in my car, I started off my resetting the ECU (test 19, subtest 21.0, if you catch my drift). I pulled out of the parking lot, and immediately felt the yo-yo. This would mean that, since the ECU hasn't had enough data logging time, it's running on pre-programmed mode, and most likely it's hardware. My next step is to measure the MAP output (or just change it, the layman solution).

More updates tomorrow after I visit the dealership and determine they're more confused than I.

 

Ryephile --

I have also done the Test/Reset for the exact same reason. My findings match yours. By the way, I did this in October during a day with the ambient temperature (as reported by the OBC) of 60 degrees.

But let's just say it is a faulty sensor. Why would BMW/MINI want to address this with software rather than a TSB? Perhaps they have not actually researched the yo-yo and are hoping that the Siemen's Stumble Fix (SSF) would address it.

Obviously, the SSF has not eliminated the yo-yo. We can only hope that the MINI community (that's YOU, Ryephile! ) will use its collective intelligence and diagnostic skills to "point" them in the right direction! This brings a whole new definition of the phrase "Customer Service".

Thanks to everyone for helping to identify the cause of the yo-yo.

My two pence,

Theo