Thanks in advance for any help.

Here is the problem my car is mildly modded, I have methnol injection on a jcw car with k&N filter. After running the meth injection I fouled the factory JCW NGK spark plugs. I think used to large of an injector the first time. I started to notice at 3k rpm that the car stummbles for a second and the sound comming from the exhaust sounds like a flutter or a gurgle. So I changed the spark plugs with the NGK #7 BKR7E I think is the part number, there a colder plug my friends with turbo cars that make 400 + hp use them so I figured I'd give them a chance. Gap is set to .40, I noticed a diffrence right away the car accelerated very smoothly compared to how it did, I didn't realize how fouled they were. Any way the car drives fine, pulls hard, with or with out the methanol injection on, but between 3-4k I get the stumble as long as the cars not in boost. If the car is in boost I have no problems at all.

PS, last night I drove all the way to about 6k rpm without getting into boost, I didn't know the car could go that high with out getting into boost. I was acclerating at a fairy constant slow pace trying to stay out of boost.

 

What year is your MCS because 02-06 the MCS is supercharged and that form of forced induction has constant boost and you reach full boost at 3500rpm.

 

This is not true.

I have a gage and the VGS mod. and can accelerate very smoothly to red line without going into boost. If anything, with the VGS mod I can activate the bypass valve sooner. The bypass valve is vacuum operated which is directly related to throttle plate tip in.

 

Yes I do have a boost gauge, That's how I know that it only does it when the cars not in boost. My car is an 06 if that matters. It just started out of no where. I'm puzzled

 

might be a faulty bypass valve, do a search on it and see if the info that comes up sounds familiar

 

I have an 06 MCS and I have experienced this stumble and stall when ever i get old or dirty gas i just put a bottle of Lucas in and corrects the problem pretty quick and I have also found that going to different gas stations has done it also different qualities of gas cause the engine to go crazy. so to correct it I always stick to one gas station that i know has quite abit of traffic so the premium is always fresh and not old

 

After doing some research I believe the problem is the mini ECU. I read that a few other members were having the same problem under the same conditions. I'll be getting a uni chip soon so hopefully that corrects the problem. But I'm still open for sugestions.

 

You may want to search around a bit more the uni chip might not be the proper bandage.
Just from reading a ton of posts others haven't had much praise for its effectiveness.
Check out a GIAC ECU Flash.

 

Thanks Norm, I'll look in to it. Update the car seems to be doing it primarly in first gear.

 

my modified jcw is doing the exact same thing. I had it in today for custom unichip install to replace the MTH map hoping that would sort it but if anything it has made it more noticable. Same thing driven nicely it is no problem, at WOT it has a definate stumble at 3000.

It has only done it since adding screamin deamin ignition and nology hotwires, it goes to BMW tomorrow to run their fault codes to see what it throws and back to tuners next week to try different plugs.

 

I can fix that for you. My LDG tunes are the best out there for increased power and driveability. Stay away from piggy backs on the Mini as they just don't work. PM me for info.

 

you may want to look for some vac leaks and the like before spending the problem away. FWIW, GIAC doesn't have the most stellar rep aroudn here too. But it's ECU rev dependant as well.

Matt

 

I had the butterfly flap removed from back of the JCW airbox at the same time as fitting ignition and wires, bmw seem to think that is the problem so will be taking flap back in for refitting to see if it sorts it.

 

Hmmm, my '06 does not have this problem, it's not a JCW but seems to run like one, err minus the stumble.

How many miles do you have? Mine's up to 8,600 I think...

I would see what your dealer thinks, either way you should track this down before doing more mods!

 

anyone try swapping in a know good coil pack from another mini ? It's worth a shot before you spend big money.