Irregular boosting issue

[moi1463]

I have a 95 gsx. the problem is that the car would sometime boosts fine, drives normally. but at times, it would not hold boost whatsoever. When the car is rev'd to about 3k, the boost would sputter and feels like the boost would not hold. this happens at irregular time. from a first start in the morning or happens after 30 mins of driving when i shut off the car, and restart it right after. i have changed the airflow sensor (new), Manifold pressure sensor (new) and ECU (used). Still nothing. no check engine light is on, but read from the scanner and the code is P1400. followed the trouble shooting diagram, and calls for bad ecu or manifold pressure sensor. So i have no clue where else to look.

 

[gstjeff11]

Have you done a boost leak test?

 

[moi1463]

no i haven't, i didn't think it was leaking because when it runs fine, i'm boosting at about 14.5 psi.

 

[gstjeff11]

What turbo are you running? Cause it could be a wastegate problem. My friends 1G had the same type of problem and it was because the wastgate rod got jammed on the spring housing

 

[moi1463]

it's the stock turbo. Is there a way to test the wastegate? I'm about to upgrade the turbo, but i want to fix this problem first. So if it's the turbo, then i can kill two birds w/ one stone.

 

[gstjeff11]

Just check to make sure that it opens and closes without sticking. the stock t-25 is junk the wastegate is weak. mine would go from running 10 psi or less then spike around 18-20!