So I bought a 2003 Mini S off my best friend, came with some mods and I added some.
Mods,
Alta Intake
Alta inter-cooler Diverter
Alta %15 supercharger pulley
Alta Light weight crank pulley
Alta mechanical belt tensioner
Cat back exhaust, cant remember which but very expensive
MSD coil pack
Upgraded wires, cant remember brand
New Plugs, I had one melted when i got the car
New OEM Throttle body

So when I bought the car I knew it had a few things that needed done, the throttle body was one of them as well as the belt being replaced. I had running issues with it about a week into owning due to the melted spark plug. I found that all four plugs where loose in the head as i turned them out with my hand and only an extension. After addressing this issue i lost the belt on the highway so of course this ment a new pulley and tensioner and all that. then the next issue was the throttle body, every now and then it would give the position sensor code and i knew this when i bought the car. Finally i replaced the throttle body. I also knew of the problem i am asking about when i bought the car but my friend was convinced it was due to the throttle body.
At 3000 RPM the car will stumble, no matter what gear, hot or cold engine, it will do it. Now if you hit it and open the throttle all the way it will wake up and go, but if your cruising the highway and get in the 3000 RPM area it will fall on its face. Around town easy driving it will be so annoying. I was really hoping this would go away with the new throttle body but it has not, the only other thing to the equation is sometimes it is not as bad, like it is barely there. However I can not find any correlation when it is there and when it is not. I am a lover of older cars mostly late 80's early 90's and I know that a vacuum advance on a distributor car can have these exact same results but there is no item like that on these new cars.

I really hope i can find some help on this as I am at the end of the trouble shooting I can do without just throwing sensors at it.

Thanks,

Brad

 

These cars have a "dead spot" in the mid rev range, some are more prominent than others. Have you looked at your bypass valve? Could be sticking or you have a faulty spring.

Melted plugs are not a good sign either, did you replace the plugs with proper heat range plugs? Do you have pictures of said plug?

 

I did take pics of the pug. The ceramic of the plug fell down against the prongs and covered the electrode almost completely. One prong was missing too. As for the diverter valve I looked at that too and forgot to mention that was also upgraded by my friend when he had the car. It seams to me it is in the tune of the ECU but that is all stock not piggyback or flash or anything.

Thanks so much for the help, I think I may look at the diverter valve again make sure nothing is stressed or broken there.

Brad

 

Search these forums for Yo yo or VGS. There is a vacuum mod for earlier cars for this.

 

Here is an application guide that may help make sure you have selected the right plugs, http://new.minimania.com/Mini_Cooper...lication_Guide

and some troubleshooting tips. http://new.minimania.com/Spark_Plugs_Overview_by_NGK

Please let us know if this solves the problem!

 

Ouch....if that is happening to the plug, I would worry....maybe running lean enough to melt a valve too...
A cooler plug, maybe more octane....maybe will be OK...I'd hope that it was melted due to your prior issues..
Remember, you highest pump octane you can get, especially with a pulley....so run premium only...midgrade is "close" with it usually being 89, but with a pulley, you have higher intake temps, so you need more octane.

 

P.S.
over the years, many solutions have been found by accident to individuals "flat spots" in that rpm range...but others try them...and they don't seem to fix it...
Mini did try MANY software versions in the ECU to fix the issue...some made it worse...I was told when I had a flash but no yo-yo or flat spot that I should stick to THAT software....I did...even tuned on it...
Generally it is thought to happen cause a bit of a feedback loop of sorts as the bypass valve closes, and the car switches to boost...and temps on the intake suddenly spike, so timing gets pulled momentarily, or some variation....
Pre 2005 cars had more issues...those cars were sold with a pretty soft bypass valve spring....in 2005 mini started to use a stronger spring, copying (but still slightly weaker) than the DT tuned aftermarket version of a reworked OEM unit...it seemed to fix the issue for many folks.
Some like the DT unit...some don't... It kinda slams shut..makes finesse driving around 3000 rpm harder..
Similarly the "vacume gain" mod was similar.giving the bypass valve a bit of extra suck to help the diafram in it shut it faster and more securely.
A few basic check are worth it...but IMO avoid chasing ghosts....

 

Ok so i got a look at it yesterday for a bit, It has an upgraded bypass valve on it from Detroit something rather, my friend told me the real name. So next I just wanted to make sure the vacuum line to that was good and all other lines where hooked up. everything looks good in that manner. The more I read about this problem the more I feel its not fixable. I will be getting a boost gauge to hook up as I have always put a mechanical gauge in all my boosted cars just did not get to it yet.
As for the plug failure i think that was an isolated plug incident as the other plugs looked very good and that fixed the running issue I was having No i did not do a compression check yet but i wail do one later this week hopefully. I replaced them with plugs that where recommended on one of the aftermarket vendors and I looked at the plug list that was linked and they are the same temp as what I put in, perhaps i could just go a step cooler anyway and see what happens. I did gap them to the parameters I found online.
I do only run 93 in this car as well as several of my other cars, only beaters get regular. So i do not feel a gas issue to be part of the problem. I will wait to give her a major tune up till next spring since it was done just last fall and has not seen many miles since.
One other question is where do i get a dip stick that does not break off? It came with a broken dip sick in it so i bought a new one on RockAuto, the first time I stuck the stick in it broke. I really don't want to have to buy a new dip stick each time i want to check the oil. I usually check every car every time I fill the gas tank.

Thanks so much for the all the help, I will have to do more work, I am also having a water leaking issue into my battery box that I am having trouble finding. But i have all the interior of the car out from the front seas back to get the head liner out. So that should help.

Brad

 

Look at the gasket around the 3rd brake light....it is foam, and goes flat...I just added some "form a gasket" to mine (brush on)let it it dry, then pushed it back in, no issues.
If you have a sunroof, you might want to PROACTIVELY remove the factory clamps and use worm clamps under the headliner to prevent leaks if it has not been done already...a 15 minute job in mist cases, headliner in place.
The dipstick fails where the yellow meets the black.fiberglass shaft...
CravenSPEED makes a nice one, or just get a new OEM one....

 

I had the same issue around 3000 RPM with my 02S and in my case it was going way rich and causing a noticeable stumble. It took a custom tune to finally get rid of it,
As for the dip stick issue as was mentioned earlier the Craven unit is very nice but pricy at $ 75. One thing to keep in mind is that if you get one be sure to dab a little oil around the two sealing O-rings and it tends to stick in the tube and a bit difficult to pull out to check. Not a big deal and a nice piece over all .