gsxranger

iTrader: (2)

I just bought a very straight, completely stock 87 turbo II. It has 120K, and hasn't been driven much in the last 10 years. It starts and runs well, but is gutless. The underhood is totally virginal.
The boost guage does not move when driving, or moves minimally to about -15, and when the car is hot, there is a popping noise on deceleration from the "turbo area". This is a hard noise to describe but is sounds like a card on bicycle spokes, but slightly more metallic.
Even though it spun fine with my fingers, I assumed the turbo was shot, so I replaced it with a known good turbo (at least I got to port the wastegate), bolted it all back together last night, and AGGGH! same symptoms. All the heat shields are tight and in place (no rust on the bolts - nice!) and nothing is obviously loose.
When I key the ignition, the boost guage does climb to -15, should it go all the way to 0? What is that noise!
Any help is appreciated!
Thanks

RXSpeed16

iTrader: (41)

If you are only reaching -15 mm/Hg on your boost gauge, you are still pulling vacuum and basically running like a tired NA engine. This would explain the lack of power. Sounds like you are losing the air coming out of the turbo or losing the exhaust gas feeding the turbo.
Some items to check are:
-Extremely clogged air filter.
-Check that the pressure sensor is fed from the upper intake manifold without leaks.
-Double check your intake hosing is intact and connected securely. Especially @ the AFM.
-Test the Air Bypass Valve between the turbo inlet and charge pipe. Make sure it isn't stuck open.
-Inspect the manifold for cracks. You'll probably need to remove some of the heat shields.
Hope you find something easy to fix.

gsxranger

iTrader: (2)

Thanks for the reply

I finally got all the fluids changed out (including getting 5 gallons of 3 years old gas out of the tank) and just took it out on the highway. I let it run at 6K rpm, taking it up and down the rev range, and it just kept running better and better. Finally on the way home it kicked up and boosted. Now it is running pretty darn well, and pulls and boosts just fine on the guage. There is a lot less of that sound. I wonder if the cat wasn't (isn't) just really plugged up. It is the stock exhuast.
No wonder people love these motors, sometimes they fix themselves!

I carefully checked all of the hoses and connections when I put it back together, and the turbo housing has no cracks. Perhaps the popping sounds are back pressure in the exhaust system?