my 88 supra seems to be having a vacuum problem. no matter what the pressure remains close to zero. i have a factory gauge and a greddy gauge and they are both reading the same but get signals from different spots. ive checked all the vacuum lines. you can hear the turbo spool up and blow off when ya release but its still showing zero. when i drive the car you can feel the lag so something is not right. any ideas?
pressure/vacuum problem
- Thread starter sc2665
- Start date
So when the turbo makes boost the gauge shows 0psi. When it idles it shows 0psi. When you load the motor, to build boost, it is laggy. Sounds like a case of the boost leaks. Make a boost leak tester and find them. Where is your Greddy gauge getting is signal from? Any codes?
its not just that its not building boost. shouldn't there be some points before boost when its under vacuum also? if it was just when it was supposed to be under pressure then i would think its just boost leak.
the greddy gauge has a t in line in a different spot from the factory gauge
the greddy gauge has a t in line in a different spot from the factory gauge
Cruising you should be at like -17 and when you get on it it will go to what ever your boosting to. If your going up hill and you give it a little more gas to maintain speed it might go up to 0-2psi.
your engine will not run with no vacuum at idle. with the engine idleing you should feel vacuum on the port for both sensors (you can feel it with your hand, just unplug the sensor vacuum line, and put your finger over it). if you dont find vacuum, move the sensor somewhere that does have vacuum.
PS the throttle body ports wont work, iirc there is one at the intake manifold near the firewall. but that one should be going to HVAC, cruse and the stock boost sensor so idk
PS the throttle body ports wont work, iirc there is one at the intake manifold near the firewall. but that one should be going to HVAC, cruse and the stock boost sensor so idk
Whats the word on this?
Could be a manifold gasket..
If you would test for Boost leaks ALL leaks would show up including vacuum leaks. There will be some leaking past the valves, but you sound like you have a good leak in there, should be able to hear it. Not sure why people think that boost wont leak out of a vacuum leak and the other way around.
Sure vacuum wont leak out of a charge pipe leak but both boost and vacuum are going to be present (not so much at the same time) anywhere after the TB. Lots of gaskets and hoses to leak back there.
Could be a manifold gasket..
If you would test for Boost leaks ALL leaks would show up including vacuum leaks. There will be some leaking past the valves, but you sound like you have a good leak in there, should be able to hear it. Not sure why people think that boost wont leak out of a vacuum leak and the other way around.
Sure vacuum wont leak out of a charge pipe leak but both boost and vacuum are going to be present (not so much at the same time) anywhere after the TB. Lots of gaskets and hoses to leak back there.
if you had a boost leak, you car would jerk hard when boosting, almost as if it were hitting fuel cut..
chances are, your wastegate is stuck open, so you're not making any boost at all...
chances are, your wastegate is stuck open, so you're not making any boost at all...