I've been having issues with poor performance, a turbo that doesn't want to build boost pressure, dark exhaust, and more recently I really bad idle that stalls out if I'm not holding the gas pedal down. There's also either belts squeeling or the turbo screeching under boost....I can't tell which it is, but the tension seems right on the belts.

It's an 89 vert that has a Jspec S5 swapped into it. Everything is factory accept for Racing Beat 3" exhaust, FCD, and a custom stainless TID.

I compression tested with a warmed-up engine and got around 90 psi on all 3 bumps on both rotors. When I take the car for a drive I can hear air pressure being released once the boost gauge shows any pressure being built and then the engine putters badly. The turbo shaft has some play, but this is my first turbo car and I can't tell if it's too much or not. I can't see any scoring on the turbo housing and the fins seem to be ok.

I've got an appt. with Banzai Racing this coming week to do some diagnostic, but before I haul the car 6+ hours I'm hoping to eliminate any stupid oversights. Any advice on where to look for leaks would be greatly appreciated. I've checked all the couplings on the TID and from the TMIC to the turbo.

 

double check all vacuum hoses, and listen for hissing. check the intake manifold for leaks too.
what do you mean screeching? a metal on metal screeching or the whistling of fast moving air?

 

either metal on metal or a belt squeel, it's high pitched and usually can't hear it well over the exhaust and other road noise.

 

going to be checking things over today. I know cause of the heat of the engine and age of the car vacuum lines are likely to become hardened are there any other areas that are typically suspect on turbo rotaries? I hear it's hard to find a used turbo exhaust manifold that's not cracked, seems logical that manifold would be a good candidate for the leak.

 

S5 exhaust manifolds rarely crack, the S4 always develops cracks.

 

I found the leak, I'm an idiot and left one of the couplings loose....though it didn't help with my initial problem.