Turbo Troubleshooting 101

[Paul_NJ]

As a regular contributor on a tractor restoration website, I know how elementary questions can be annoying. But I've got to start somewhere.

My 87 turbo MKIII runs well, but has progressively lost turbo boost. It does not kick in as readily (requires more load, rpm) as it used to, and when it does the boost gauge needle almost seems to "come unstuck" . . . jumping from negative to mid-positive scale. I experience some performance boost, but not near as much as in the past.

I read the couple pages in the repair manual (EM-30, 31) that give some diagnostic pressure checks, and will rig up a regulator as they suggest, to test operation of the waste gate, although I don't yet know what that looks like. Other than visually, are there any tips to checking the intake air system for leakage? Guess I could always replace all the hoses.

Can anyone give me some beginner's tips for things to check, or direct me to a source of information to do so. I have waded thru the archives here, but am somewhat overwhelmed by much I don't yet understand.

Thanks

 

[suprahero]

You could have a boost leak, or a faulty wastegate or even a faulty turbo. Have you done any recent work to your car that could be causing this? Have you checked the codes?
http://www.cygnusx1.net/Supra/TechTips/engine_error_codes.aspx

Post up a little more info on your car and exactly what it's doing after you check for codes and we'll see what we can come up with.

 

[Rennat]

the stock gauge is HORRIBLE as far as where your boost actually is... i can sit at 0psi, but the gauge wont be moving. get a real boost gauge if you want to see what its really doing.

and mine "jumps" just like yours, so dont worry, your not the only person whos annoyed by it.

 

[Paul_NJ]

Thanks for the responses and the link. I'll be back later in the week with the codes.