I have a '96 850 R and I noticed that the boost is inconsistent. When it's normal the boost needle will hit about a third of the white region, but every once in a while it will boost way to the end of gauge and cut out.

I can tell when it is going to this because the turbo will spool up much louder even lower on the gauge and then if I hit it, I can get as much boost as I want until it cuts out.

I have fully tuned it up and checked/replaced all vacuum lines, so I don't know what the problem could be mechanically.

What is going on?

-Dave

 

Intercooler hoses all good?
Maybe the electronic boost controller is messing up.
Or maybe the CBV is going bad.

 

How would I fix/change the electric boost control and what is the CBV?

I am putting an IPD flashed ECU in the car, so I want to get everything right before I put it in. I bought the ecu used and got a great deal.

Are those all of the possibilities? I want to go through it and check/eliminate some of the possibilities.

thanks,

Dave

 

The Ebc is mounted on the side of the air box.
The CBV is basically the factory blow off valve. The diaphram is known to tear at times.
I would also get an aftermarket boost gauge and install it before doing the IPD ecu.
This way you know the exact boost levels.

 

Check for sticking or frozen waste gate assembly on exhaust side of turbo which requires removal of turbo from vehicle.

 

You can check if the wastegate pivot pin has popped out or not while keeping the turbo on the car, you don't have to take it out.

 

Actually my waste gate froze up internally even though the accuator seemed to be moving freely. So the only way to check this out was to remove the turbo from the exhaust pipe to see that the waste gate is fully seating to the internal exhaust chamber port.

 

I guess for that then you would have to take it out. My turbo's wastegate had popped out a bit, and wasn't closing all the way, even though I had the turbo out, I could have left the turbo in to fix it.