i have a issue that is driving me nuts. under load (3rd-6th gear) my car stumbles between 2500 and 3500 rpms. it almost acts as if it needs fuel, i loosened up the ic boot which created a massive boost leak and the car would pull through the rpm range without a hic-up. i have mth, but the car will still do it with the stock file. the car does'nt throw any codes, and once above 3500 it runs pretty good. and to top it off, every so often it runs very well. i'm thinking injectors, but would like to know for sure what is going on.

cheers

 

How is the acceleration in 1st and 2nd gear around that rev range?

 

the car will free rev , and will go thru 1st and 2nd good.

cheers

 

Noticing a similar issue, Right around 3.5k RPMs.
Mods as in sig.

 

This sounds like the age-old yo-yo problem as reported in '03 and newer MCS models. If it is the yo-yo (and BTW, some MINIs just hesitate instead of bucking), here is a thread with more information than you will ever want to know about the problem:

The Yo-Yo Chronicles

The downshot is that this is a problem related to the vacuum control of the supercharger bypass valve and, despite many attempts by MINI to fix it with ECU software, it remains present. Please note that this problem seems to affect some MINIs but not all MINIs.

I have an '04 MCS and it had the yo-yo. When I added the JCW 210 kit, it helped a bit. When I added the MTH software, it helped a bit. However, it wasn't completely addressed until I tried the VGS solution:

Vacuum Gain System

The VGS solution essentially supplies a different vacuum source for the bypass valve operation and, for me, almost completely masked the effects of the yo-yo.

However, the VGS solution DOES affect throttle response. The stock on and off boost response to throttle input is somewhat gradual; in effect "smoothing" the perceived boost response. VGS seems to eliminate the smoothing and create a more binary feel: just boost-on or boost-off. The upside is that tromping on the throttle will give almost instantaneous boost, snapping shut the bypass valve...but letting off the throttle snaps open the bypass valve and the resulting loss in boost is quite apparent. Thus, the VGS modification takes some getting used to in order to drive smoothly; for that reason, some people do not like it. You may also notice a MPG or so drop in mileage since the SC boost is used more frequently.

Then again, the VGS solution costs about $10 and about an hour of your time. It is also completely reverseable.

FWIW,

Theo

 

*****,

I'm troubleshooting a similar issue. I've narrowed it down to the wiring harness/ wiring connector to the coil pack. I've got a bad connection. If I play around with it I can get the car to work well enought to drive. When I get the car under load, then it misses and will eventually throw a P0300 code (random misfire). Sometimes it will report a P0302 code (misfire cyl 2). The more load, the more likely it is to misfire. FWIW, I've been having this gremlin since before AMVIV. I even ran the track day with it misfiring...but I was able to get the wire/connector aligned just right so it wasn't too much of a problem.

 

hey bud, you are on the right track!!!! i just went out and check the coil pack connection, the wiring harrnass was very taught, took the harrness clamp off the valve cover and pushed the wires back into the connector. shazzamm no misfire or stumble. it started doing it again, got out and did wiring trick no misfire. great call, thanks alot.

cheers

 

Sounds like all is well, thanks to the electrical fix. However, if it returns, I'm still betting on the YoYo as the culprit. The VGS *is* the fix for that. 30minutes and under $10.
cheers, phil

 

sorry, i have already done the vgs mod, the problem started shortly after i installed my ported head, i'm thinking that when i hooked the coil back up there was not enough slack to allow the motor to move. this is why the problem did not surface right away and was getting worse as time has passed. time will tell.

cheers

 

problem comes back when the engine gets warm, back to the drawing board. bad bypass valve perhaps.

cheers

 

Bummer...I hope you get it figured out.

 

I also had that problem.

I first did the VGS mod. It helped quite a bit, and was a cheap solution, but I stll had some Yo-Yo problems...

So I got a Detroit Tuned supercharger by-pass valve. It helped a lot more! but the Yo-Yo was stil there a little bit (very little, in fact this mod go trid of 95% of the Yo-Yo problem)

Then I got the MTH Tuner Version 7 file uploaded and everything is alright now!

 

this is not yo-yo, my defination of yo-yo is when the car starts to jerk as if you were gas on gas off gas on gas off when actually the throttle is in one position. this thing is misfiring and only when it is hot, when first started it will run normal, after it gets warm it starts it's fits.i put the car in 3rd gear at about 2000 rpm and punch it it starts to accelerate and with my foot to the floor it will start missing around 2500 rpms and will continue till around 3500 then it will clear up and run fine at higher rpms.


cheers

 

Thanks for all the info!

 

Willy69

Check out this thread I started, which lists a very similar issue:

https://www.northamericanmotoring.co...ad.php?t=62919

After the loss of power issue, we had couple of instances where our MINI exhibited the same symptoms you mentioned, without any warning lights.

The service engineer at our dealership told us that this MIGHT be linked to the faulty clock (gaining time), since the CANBUS communicates through the wiring in the instrument cluster. I am getting the instrument cluster replaced on Monday and will post an update after that!!

 

thanks for another view,but my car does'nt die.



cheers

 

i went out and did some 1/4 times, this car was doing 13.3-13.6 times consistanty, 0-60 5.14-5.6 consistantly. now the best was 15.7 and the best 0-60 was 7.1. this is nuts. i can not get a code i changed the vgs mod back to stock, anybody ever have coil issues? the bypass valve looks and feels as if it is working properly, can injectors act up with out throwing a code? does anyone have a sledge hammer handy?

 

well folks it is solved. i don't know if i should tell what the problem was as it was pretty stupid, but here goes. i started getting a p0301 code which is cyl 1 misfire, since i have justed changed the head i was afraid of head issues so i did a comp test, all cylinders were 155. then i swapped injector 1 to 4, still pulled the code. today i decided to stop thinking and use a little common sense. i thought if one of our race bikes started acting like this what would i do. change the plug!!!! i replaced #1 spark plug and presto this car runs like a raped ape. after inspecting the plug it looks perfectly fine. moral of the story quit thinking



cheers

 

Glad your car is back to normal! Sometimes the easiest solution is the best one.

This is the funniest thing I have read all day.

 

*****, glad to see you figured out the problem.

I too finally figured out the gremlin going on in my car causing the misfire. It was a combination of coil-pack and engine wiring harness.

The stock coil pack connected to the stock wiring harness would exhibit the problems I describe above. When connecting the screaming demon coilpack to the stock wiring harness, it made the problem worse...much worse...it wouldn't even idle correctly.. Hence why I thought the screaming demon coilpack was bad and have been running with my original stock coil pack.

So after I get the engine wiring harness replaced, the problem still was there. So in despiration and curiosity I tried the screaming demon coil pack I had sitting there. And all was right in the world. My car runs again cleanly. No more rought starts. No more misfire codes. No more stubling on heavy load with part throttle. Whew!

 

I have had the same issues. P0300. I have changed plugs, wires,coil,injectors,TB have taken every connector I can find apart and put back together. Will let you know when I solve it.

 

Finally worked on the connector to the coil. Cleaned pins on the coil and pried the female connectors tighter put elctrical inhibitor on the connection.
Pulls thru all rpm ranges no miss fires. Whahoo