wAnKeLiSgOd

1. Working on a bone stock 1985 12A engine
2. Engine was transplanted from car with 72K mi. In 1988 the car was wrecked and the owner garaged it up until about three years ago. I bought the car for parts.
3. I installed the engine/trans in my 1985 GSL. After changing plugs, wires, rotor, fuel, fuel filter, oil, the engine fired right up. I was told the car ran perfect when parked, so I didn't mess with any carb settings, timing, etc. After first warm up, there was cycling between 900-1100 rpm. I pulled the cover off the air cleaner and there was sputter from the Shutter valve port which coincided with the cycling.
4. I checked the shutter solenoid, good. I checked whether the vac tubes were good in the rats nest, they were good. I checked the vac lines going to the shutter, good. On restart I could see the shutter rod moving in and out in unison with the cycling. I put a vac pump on the shutter, would not hold a vacuum, would not hold rod "in".
5. Removed the carb, shutter. Mechanicals in intake manifold good, working properly.
6. I removed a used shutter from the former 12A. Applied vacuum to the solenoid hose. This shutter held vacuum, it held the shutter rod "in" until I released the vac.
7. Installed this one in the car.
8. Cycling gone.
9. But, No power, engine sounds like leaf blower. I pulled off the air cleaner top, steady sputter noise coming from the shutter port. Idle 1100 rpm. Placed finger over shutter port, idle drop to 800. Smooth. Taped port closed. Power great.
10. If I remove the tape on the port, I can see the vacuum pulling the shutter rod "in" and holding it. But this makes the car run poorly. if I tape the port, the shutter rod extends and the car runs fine.
11. Looking at the shutter, it appears there is a dual vacuum use for the part. One is the hose coming from the solenoid. Where it bolts to the intake, there is what appears to be a vacuum hole. There is a small access plate held with two phillips.

Is it possible the access plate is leaking, causing the problem? Did I install the shutter wrong? Where the shutter rod attaches to the intake flap, I attached it to the "inner" hole. There are two options for attaching. Did I mess that up? Anyone have any ideas?

j9fd3s

iTrader: (3)

i would say somehow its not installed right...

wAnKeLiSgOd

Here's the update. I rechecked the solenoid and it checked out OK. For ***** and giggles I checked the voltage at the yellow plug with the key on. It registered -3 volts. How you can have a negative voltage I don't know. So, unplugged the connector under the washer bottle and checked continuity on the shutter plug and both power and ground tested fine. My next step will be to test the computer.
This car is from California and the engine is from the East Coast. Did California cars use different computers?

boyee

iTrader: (3)

california emissions were different than everywhere else so possibly the emissions computer is different. rats nest were different to (the orange pug wasnt used)

j9fd3s

iTrader: (3)

[QUOTE=wAnKeLiSgOd;9589712
This car is from California and the engine is from the East Coast. Did California cars use different computers?[/QUOTE]

yes, but the shutter valve is the same.

i wanna say if it sees zero throttle, above a certain rpm (1200? 1500?) that it should turn on the solenoid and suck the valve closed. a bad/misadjusted TPS will cause weird things to happen, and yes there is one.

swapping motors i would not have unplugged the wiring from the solenoid rack, but if you did, maybe you have it hooked up to an ACV solenoid or something? that would suck the valve in at idle....