Car is an 87 T2 with what looks to be a 2.5" exhaust. Has sat for 2 years untill today. some times the boost gauge (stock) reads normal, other times its at 0 some times its reading vacuum. I don't think its creeping. It feels like its boosting, but when I accelerate it drops. sometimes it may be boosting more than others. PO said it has a FCD defender. little black box mounted on passenger strut tower. I don't know if he was just saying that is what it was or if it really is. I'll try and get a pic of it tomorrow. I figure if it is what he said, I'll pull it out till I get things all up to snuff. its definitely gets up and go's when I press the peddle. so I'm sure even though its saying vac or 0 I'm getting boost. also idle is really low and bouncy. it goes between 500-600 RPM. Other than a few electrical issues car looks and runs great. Really needs a bath.

And one more turbo newb question, can I use any kind of injector cleaners, or sea foam. Also how can I keep my car from boosting so I can run ISO heet to pass DEQ? Its just a sniff test with a under car visual. exhaust is legal.

 

check your tid, my car started doing that sure enough...tid had a huge crack in it from over the years I assume but replaced it and I went back to stable boost pressure or you could have a boost leak somewhere, might want to check your couplers that go to your inter cooler

and btw you is your car s4 or s5?

you will never get the correct boost pressure with the stock guage because the FCD is tricking it....

 

The stock boost gauge is not the greatest on these cars. Just verify with an aftermarket install.

 

^^^^ Agreed.

Pick yourself up a Prosport electrical boost gauge. Best $90 I've spent so far.

 

cool thanks. I was already planning on getting a aftermarket gauge. I have the pics of the FCD device in question. Or what he told me it was. BTW its a duel 2.5" exhaust not just 2.5" I just wanted to clarify that. Car is a S4.

So what about the crappy idle. If I place my foot on the gas ever so lightly it goes up to about 750RPM and smooth as silk. when I let off the gas it drops to 750 idles smooth for a few seconds and goes back down to 500 and bounces up and down. car shakes. Could my throttle cable be stretched. could the linkage just use some lube, or do I have a bad ground? There is some electrical issues that mostly occur when its idling ruff.

 

I sounds like you have a vacuum leak. Like someone here posted already check the turbo inlet duct and also check the vacuum line going to your Pressure sensor

 

I don't think anyone said vacuum leak. It turns out that's what it was. I pulled the intercooler and checked the lines. found one that would leak when you moved it around. I taped it up till I can find the part number for the hose. Idle is smooth now. I'll be getting a boost gauge ASAP. Thanks for your help.