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Thread: Celica ST165 Can't find my turbo pressure sensor

  1. #1
    Forum Member 1st year Apprentice
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    Oct 2011
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    Default Celica ST165 Can't find my turbo pressure sensor

    I have a 1988 Celica ST165 which is in good condition and unmolested (quite stock). I have only purchased this car about 5 months ago.

    Now the problem I have is that I am only getting about 3 pounds of boost (flat out). I have done all the vacuum checks. The turbo is in good condition and the waste gate is operating satisfactory.

    How ever, for the life of me, I can not find the Turbocharging Pressure Sensor. I found the Turbocharging Pressure VSV, the Vacuum Tank, the T- VIS VSV and the Fuel Pressure VSV. They were where the workshop manual said they would be, behind and at the bottom of the inlet manifold. According to the manual, it should be hanging off the firewall.

    I wonder if the previous owner removed it for some reason? I have found a vacuum point on the manifold with a bit of vac hose over it with a screw in it blanking it off and a large white electrical socket close to the point not connected to anything. I have checked the ECU and the connections are there. As previously said the car starts ok, runs ok, idles ok, but performance is limited to 3psi boost. (yes I have checked out the boost gauge too.)

    So is there some one out there that is familiar with the GT4 and knows where this little valve is hiding?

    Cheers
    Senior fred
    ,

  2. #2
    Fear the Rapeodile Carport Converter blakeg's Avatar
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    Default Re: Celica ST165 Can't find my turbo pressure sensor

    well first off. vsv or not, if you have the wastgate hooked directly to the air supply you should get 7 psi , thats wastegate pressure. so somthing is amiss. any error codes ?

  3. #3
    Forum Member 1st year Apprentice
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    Default Re: Celica ST165 Can't find my turbo pressure sensor

    Quote Originally Posted by blakeg View Post
    well first off. vsv or not, if you have the wastgate hooked directly to the air supply you should get 7 psi , thats wastegate pressure. so somthing is amiss. any error codes ?
    Bit confused here. The waste gate actuator is directly hooked up to the Turbo and the second vac hose (vacuum pressure relief) is hooked up to the Turbocharging pressure relief VSV. On test as per the manual, the actuator rod moves at about 9 psi. Do you mean clamp off the second hose and see what pressure reading I get on the boost gauge?

    As for error codes, how do I do that? Do I need a diagnostic hand analyser gisso and plug it into the car diagnostic plug?

    When driving and accelerating, the green turbo light on the dash comes on ok. Now that must be vacuum connected somewhere?

    blackeg, thanks mate for giving me a hand I do appreciate it.

    cheers

  4. #4
    Junior Member Grease Monkey
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    Aug 2010
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    SA
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    Default Re: Celica ST165 Can't find my turbo pressure sensor

    The vac line goes from the turbo to the wastegate actuator diaphram, with an outlet from that going to the TVSV. Wastegate should open at ~7psi, and if the TVSV is open it will bleed off some of the air so the wastegate won't open till ~10psi. The only boost 'sensor' on the gen 1/2s runs off the intake manifold to a MAP that is used to trigger fuel cut.

    If you're only making 3psi, you've got a major leak somewhere or a wastegate problem. There is no way for the ECU to limit boost below 7psi.

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