300zx no boost.

[submachine69]

i have a 91 twin turbow 300zx and latly if i get on the freeway i get it hot and then all of a sudden i have no boost at all, i was whondering what all factors play in to the car haveing boost, i know u must have good cylinders that can push out hot exhaust gas to spin the turbo and u also need a free flowing exhaust too, but i was whondering how the waste gate controlled and is it only vacuum lines or is there a valve that can allow vacuum or prevent it that may make the waste gate stick open. i cant hear the turbos spool up so i know its not on the intake side. please if anyone has run into a simalar situation.

[Hodo]

I havent had this happen to me but I dont have turbos.... I would be rather surprised if I had a sudden boost surge on my NA.

All kidding aside. I belive the stock turbos on a TT are vacuum controled wastgates integral on the turbos. But these are also controlled by the ECU. which if there is a problem your ECU will go to safe mode and cut boost. You may want to pull codes and see what you get.

And let us know what you find out.

Now I am sounding like the techhelp line for Volvo....... God I need a new job.

[robzone0911]

Originally Posted by submachine69

i have a 91 twin turbow 300zx and latly if i get on the freeway i get it hot and then all of a sudden i have no boost at all, i was whondering what all factors play in to the car haveing boost, i know u must have good cylinders that can push out hot exhaust gas to spin the turbo and u also need a free flowing exhaust too, but i was whondering how the waste gate controlled and is it only vacuum lines or is there a valve that can allow vacuum or prevent it that may make the waste gate stick open. i cant hear the turbos spool up so i know its not on the intake side. please if anyone has run into a simalar situation.

If you are bone stock your ecu controlls boost... if you have an aftermarket boost controller it will have a solenoid that controls the boost. You may just have a major vacuum leak. since any vacuum line connected to the plenum turns to positive pressure when you boost you wouldn't really hear a major leak until it's under boost. Listen for any hissing under the hood at idle. You can also try a boost leak tester.

[k3smostwanted]

major boost leak...

[stprasinz]

Does it have the power of boost? only doesnt show up on gauge?
Wastegate stuck open?
good luck.

[Eclipsewhipping]

poop

[Tach_it]

Originally Posted by robzone0911

If you are bone stock your ecu controlls boost... if you have an aftermarket boost controller it will have a solenoid that controls the boost. You may just have a major vacuum leak. since any vacuum line connected to the plenum turns to positive pressure when you boost you wouldn't really hear a major leak until it's under boost. Listen for any hissing under the hood at idle. You can also try a boost leak tester.

I agree get a boost leak tester, it connects right in front of the MAF. It is possible to have a vaccum leak also so look for both and get a spell checker.

[stprasinz]

I still want to know if thats just on the gauge or does it not feel like boost....Aftermarket (mechanicle) gauge....

[apostrophe28]

you say its only when the car is good and hot?...when was the last time u changed ur spark plugs..and when u did, did u gap them correctly?

[stprasinz]

Still wondering