Help with boost hesitation on 87 z31!

[Garrett76Zt]

Hey Guys, I've been trying to diagnose a problem with my friends 87t for a while now. Here's the rundown:

 

Problem: When the car builds boost it doesn't accelerate hard at all. Basicallly feels like the car is N/A. The one exception is during the first 5 min or so when the car is cold, it pulls hard like it should, but when it warms up it won't do crap. (highly technical term)

 

1. Car idles fine and revs freely when not in gear

2. Car passed emissions just fine

3. Installed boost gauge and it reads 16.5 psi vacuum and builds 6 psi boost. Car is stock by the way.

4. I pulled the intake off and checked play on the compressor wheel and it feels nice and tight.

5. I've gone through and tried to look for vacuum leaks, replacing a few lines and couplings but this had no effect. 16 psi seems low to me though so perhaps there is still a significant leak somewhere.

 

This problem first arose after the car overheated badly one day, the water pump went out. So perhaps this is related.

 

Is it possible that the FPR is not referencing boost correctly and not giving enough/too much fuel under boost? Ignition?

 

Somehow I think it is temp. related to the overheating and the fact that it drives nicely when cold.

 

Sorry for the long post. We really want to bring this car with us to SEZ so your input is appreciated! Help!

 

Garrett

[SleeperZ]

Bad plug wires or plugs?

 

??

 

It had somewhat the same symptoms on my Z...cruise was fine, load it, it fell on it's face.

[john kosmatka]

Yeah I would say plugs too. Just solved this problem on my dad's saab, same exact symptoms.

[Garrett76Zt]

Any explanation for the fact that it drives well when cold but not when warm? Really pickin my brain on this one.