I'll explain my back story:

I was out driving with the mavs (maverickminis.com) and in the middle of a turn started getting some pretty bad stuttering and power loss. Problem seemed to pop up everytime I went over 6k rpm.

So, since I'm still under warranty, I took it to the dealer. They said it was a bad bypass valve, and replaced it for free. Also said my belt was a little loose and I should look into getting a smaller one. Now I have a 15% pulley, for reference (no smaller crank pulley either). The belt I did not put on myself, so I cannot say exactly what size it was (done by Jacques at BBM) however after the dealer replaced this valve the problem went away.... for a week. It's back now, so I took it back to the dealer. This time, they claimed it was the belt. Doh. I stopped dilly-dallying and put this belt on instead: Gatorback 4060537

The power loss @ 6k problem is BETTER, but not gone. It still seems to slightly stutter at high RPMs, and I'm still throwing code P1237 (Secondary upstream manifold air pressure sensor low input) every time I driver around moderately fast.

Any ideas? Mod list is in sig if it helps.

I'm not a huge gearhead, but I'm about ready to take it to the dealer or a decent MINI shop and say "Make It Work" and eat the expensive labor / cost if I can't figure it out :(

 

IC boots on tight? Sitting in them ok, no kinks pinches nicks or leaks? Have a boost guage? If you can go around the engine bay, at idle, and not hear any leaks that is a good sign. I've heard of lots of high MAP sensor readings at high RPMs where the car (setups not too far from yours) have more boost than the sensor can handle, but don't recall a low reading. How long have you had the MTH and is it configured to all of your drivetrain mods?

Might want to search for VGS (Vaccum Gain System) look at the diagrams, check the connections on your exsisting lines, and before spend lots of $$$ at a shop, give the $5 mod a try (and take maybe 5-10min if you're good with the IC on/off procedure), its effect varies car to car and is difficult to measure. Doing the VGS in your case might be more of a "quick fix" than a root problem adjustment.

I'm on the lack of sleep side of things right now, if I think of anything else I'll come post it. I presume no audible belt squeal or driveability changes in the lower revs?

 

Heya, sorry for the delayed response. I checked the IC and one of the boots was pinched (BY THE DEALER!) however fixing the pinch didn't remove the problem.

I assume by VGS you mean this NAM post.

I'll check it out. Per a friend's suggestion I should try tying closed the bypass valve which sounds like a similar mod to this. However I am looking for something longterm since my commute is 40 miles total a day and it's my only car.

Can't wait until Monday (or maybe Wednesday since monday's the 24th) to call up the dealer and ***** about my pinched IC boot and one of my IC air diverter threads being damaged

 

Which Bay area dealer did you take your car to? Seems like one that is fairly friendly to mods.

 

I go to mini of mnt view. I can't say I've had problems in the past.

 

Yeah that's the VGS I was talking about, do you have an OBDII tool? I figured the boots would've cleared the code, but the 6k+ would need some bypass help. Have you managed to find any other leaks in the lines or a loose fitting?

 

The code your getting pertains to the upstream MAP sensor, which sits on the driver side of the cylinder head, near the thermostat housing. It's fed by a plastic tube that plugs into the supercharger housing inlet. If this line was cracked or pulled out from the blower, you'd likely get the code you're seeing. Also the MAP sensor itself might be going bad. The dealership SHOULD know this, but how many times do they ever get it right [sigh].

This sensor and the line for it are a bear to get to or even see. The easy way is to remove the air filter box and get a good flashlight.

Good luck,
Ryan