The good, the bad, and the leaky?

[Jeff]

Just bought a 70,000 mile '84 GN, bone stock with the exception of the air filter. I'm having a little trouble with it though. I've seen a couple of other old hot-air posts with the same complaint, but no solution.
When I launch, everything seems fine the turbo starts to produce boost and I get impressive acceleration up to about 8lbs. of boost on the factory gauge (I hear these aren't accurate though). Then from 8-15 lbs. the acceleration just dies. Also happens when I get on it from a roll. I put my foot in it, the tranny downshifts, starts to boost and accelerate, then the boost gauge pegs into the red and performance dies. A friend mentioned the possiblity of a turbo leak somewhere, and I do hear a hissing air noise when I hear the turbo spool-up, but I'm new to these cars and don't know if that's a normal sound or not. Is this a healthy sound? Could this be a turbo or vacuum leak? If so, would that explain my problem. Or should I be looking into sensor or ignition problems. I know I need a scan tool, but while I saving up the scratch for one, I thought I'd see if anyone had any ideas.
Thanks to all for the replies.
jeff

[SLOW_85]

Could be a leak at the turbo to intake adapter,up-pipe or a vacuum line.
The intake adapter has o-rings to seal. Chances are you have some header leaks.
Common on these cars.
If it's not missing,stumbling the ignition,maf sensor is probably ok.
I have some vacuum diagrams here:
http://www.geocities.com/gnowner85/info.html
Need to run high octane to eliminate knock.
HTH

[Jeff]

Thanks for the info. I'm running 91 octane, it's the best I can find around here. I've also been wondering if maybe I wasn't getting some detonation as the tubo spools up, causing the computer to pull timing. Guess I'll have to wait for the scantool.
As far as the "air" noise goes, do you hear any of that on your '85? Or would this most likely be a leak?
It seems like it would be relatively easy to find leaks on the turbine side, but how would you go about finding them on the compressor side? Or should I instead just treat the points that commly leak as though they had a leak and hope I fix any?
jeff

[Jeff]

By the way, nice job on the website. The diagrams are great.
jeff

[SLOW_85]

Shouldn't really hear any noises.
Use carb cleaner or WD-40 & spray everything at idle.
Does the rpm change? Don't spray any sensors.
Could have a loose connection somewhere or bad seal.
The vacuum lines get brittle over time,due to the under hood heat.
If you have an adjustable wastegate might try turning the boost down with 91 octane.
If you have a voltmeter you can check your TPS sensor.
http://www.gnttype.org/techarea/maintenance/TPS.html
I have an extra version of T-Link 2.13 if you would be interested.
Main thing is take it easy till you get things figured out.

[Jeff]

I'll give it a try. Also, I am interested in the T-Link 2.13. I just sent you an e-mail.
jeff

[buddiiee]

hey, i have a very good cond. 87 that does the same thing. i dont know where the boost is when it dies but, when i get on it, not punching it, but not driving like a gradma either, it acclerates really quick, to about 50, then the acceleration sucks after that. it goes, no smoke, hisses or knocks, but its just not responsive at all. it sounds like its trying to go 20000 miles an hour, but its only going 60. i mean rps are maxed, boost is maxed, its trying its little heart out, but im only going 60. acceleration from 0 to 50 is like a corvette, from 50 on, is like a cavalier. any suggestions? could this be a vaacum leak? i think i may have one, but, would such a small problem cause all of that? do different vacuum leaks in different areas affect different performance features?