Help. My mini needed a new supercharger. So yesterday I installed a low mileage unit. I did get the bypass valve pinched on the throttle bracket while installing and I think I ruined my bpv. As the code I read relates to to hi pressure during deceleration. The bpv looks like it is moving. Rpm at idle is just sub 1k. The new supercharger has a 15% pulley. I doubt this problem has anything to do with the supercharger or the pulley. It is probably because I bent something on the bpv. Anybody have any opinions or experience with this? I need a smog in 4 months and I have to get this sorted out.

 

I replaced the bypass valve and the map sensor today. The code comes back every time. I am at a loss why this code is there. The only thing I can think is if I put a stock pulley or a 0% back on. Does anybody have experience with this? Smog comes in October so I have a few months.

 

Double check the lines into the S/C for damage or that you got them re-connected properly, sounds like you're loosing pressure/vacuum somewhere, either that or you accidently damaged a map sensor.

 

This is my thought now too. Being that the bpv and the map sensor is now new and the car acts exactly the same. I suspect some vacume loss that is preventing the bpv to operate fully. The car has 190 k miles and drives great. So I would not be surprised is there is a hard fragile piece of rubber that does not seal correctly. In fact the hose that runs from the bpv to the plastic plenum is very hard and crumbly. I wounder if my leak is there. Thanks for the thoughts.

 

The code P1242 Secondary Upstream Manifold Air Pressure Sensor Too High in Deceleration. IMO your bypass valve is not working properly. Your By-pass valve may be sticking or is stuck also check the rubber boots on the intercooler, they may have slipped when you tighten them causing an air leak.

 

I'm going to put my stock intercooler boots back on. The bpv has been replaced so now I'm chasing a leak that is preventing the bpv to operate correctly. Thanks for the tip on the boots. I'll check them.

 

Absolutely, I missed that in your sig. the OEM boots while not that pretty, work the best.

 

Had the same code on mine last summer! Found out that one of the stock intercooler boot was cracked. Exhaust manifold turned bright red (running lean).

 

Keep us posted.

 

I wanted to update this post so a future reader would not be left hanging if they were researching this same code.

I took off my By pass valve, and throttle body. cleaned the throttle body because it was dirty. I replaced the hose from the By Pass valve to the plastic plenum. it is a 1 5/8" hose. used standard screw hose clamps. My hose was hard and brittle. When I removed the BPV the first time it got a hairline crack in it. So time will tell. When I replaced the hose I disconnected the battery but forgot to clear the code first. When I restarted the car. the code was still there. So I cleared the code and when for a drive. relising that the code would usually return after I turn off the car and restart it, I did this a couple of times. So far no code. I have my fingers crossed that I fixed it. Down side- I replaced the BPV when I didn't need to and the MAP sensor too. Oh well. If I paid someone to fix it. they probably would have done the same and charged me a ton of labor. I also replaced my intercooler boots with the stock boots. The stock boots do look worn and show some cracking. I'm going to start inspecting for cracked hoses and ruber components. After 10 years and 190K miles the rubber on my car is getting hard and cracking.

 

My code came back. So now I think my problem is deeper. Going to check the plenum and connections.

 

Ok I found my problem. the vacuum tube from the plastic plenum to the manifold air pressure sensor had broken. when this is replaced it should fix my problem. part number 11651504943. I have epoxied the old one together but the new one wont be here until monday at the latest. Saturday if Im lucky. So I hope the glob of JB weld will hold until then.