Boost psi and knock sensor

[habitatguy187]

Ok I searched around quite a bit and came up with nothing. The truth is that I'm having two problems, number one is that my CEL clicked on and off several times and turned out to be code 31 (knock sensor) I bought a new one today but had some trouble installing so i'll try again on thurs. Now my second problem is that I installed a boost gauge last weekend and it only shows 7-8psi of boost. It was my understanding that stock boost on a 1g is 11psi?? So I was wondering if a bad knock sensor could hold back my boost levels or is there something wrong with the gauge? Thanks.

 

[Cooper4X]

check for boost leaks. if you are on soft pipes still you probably have all kinds of leaks (even if they are minor they add up)

 

[habitatguy187]

check for boost leaks. if you are on soft pipes still you probably have all kinds of leaks (even if they are minor they add up)

I checked for leaks just 2 weeks ago and came up with nothing. I guess I'll do it again on Thurs. when I have time. I'll keep you guys posted.

 

[bastarddsm]

I checked for leaks just 2 weeks ago and came up with nothing. I guess I'll do it again on Thurs. when I have time. I'll keep you guys posted.

Haha why yes in fact it does. It just so happens that I have been reading the ECU Code. its about 20,000 lines long.

Basically what happens is that when the ECU has a Code 31 active, it does lots of things, most notably it puts in a failsafe for the knock retard function. In closed loop, it always shows 0 Knock, but in open loop it shows 8 counts. This causes the timing to be reduced. Also It fixes the BCS closed, limiting your boost to about 7-8 psi. Finally I am pretty sure that it fixes the octane value to 0 so that you get shit for timing advance. This is what I can make out of the disassembly I'm going through right now.

 

[r1991_4g63t]

oops

 

[habitatguy187]

Ok, so I finally replaced my knock sensor last sat. (had to use air impact tools!) and everything is ok now. My boost gauge is working fine, have it turned up to 12psi and no problems. So now I know that low boost can be because of a bad knock sensor, and so do you.