I'm about to buy this car and i need a question answered first.

It's a 90 TII... this is what happens.
I turn it on, the boost gauge drops to the far negatives (indicating good vacuum?)
I gas it and when it's supposed to be at full boost, the gauge reads like 10mmHg.

The turbo has 124k on it... what does this mean???

 

The stock boost guage sucks. But if its accurate 10mmG should mean about 14lbs of boost which doesn't sound accurate to me on a stock turbo.

If its stock that is.....

 

um.... no... the stock boost guage goes up to 45x10 mmHg... i think you got something backwards..

new NEWS: I just filled the car with decent gas, as it was running low on fuel... (about a 1/4 tank left) and now the boost reads to about 25mmHg under full throttle... maybe I should siphen the whole tank out and fill it all with premium... hmmmm

any opinions?

 

slap an aftermarket on there...you dont have to mount it if your just trying to get a good boost reading....then it will tell you what is really up....
and if you get the car, then you already have a boost guage to attach

 

Apparently there's a sensor that tests the octane of the gas and limits the boost accordingly. Would premium make it run at full pressure?

 

if its a turbo you need to run premium PERIOD...
nothing less than 93.....so they say.....it needs higher octane tthough, that is for sure....gas is not a place to budget your money

 

nothing less than 91. In CA I dont believe many places carry anything higher than 91 other than race gas. But generally get 91 or 93 octane.

 

Boy do I feel dumb.
I thought the 45 on the dash was for 4.5PSI - Duh..

So - if full scale is 45cm, that's like .5bar or 8PSI?

 

so what do i need to do? Could it be that the wastegate is opening too soon and needs to be replaced?

 

I don't get why everyone has trouble with the boost gauge's units. It's written right there on the gauge! x10 mmHg

So full scale "45" is 450mmHg = 8.7psi

"10" is 100mm = ~2psi

Either the gauge is dodgy or sometihng is causing low boost. Usually this is clogged cats or air filter.

Besides, troubleshooting should be done with a proper boost gauge, not the dash one. Don't buy the car until you can verify it's making full boost, or you diagnosis the cause of the low boost and negotiate from there.