Did a drive just now: 19 mpg. According to the SG, the engine is in open loop constantly, even when hot.
The only thing that could fail in the dizzy is the pickup coil/camshaft sensor, and I already replaced it with the one from the ForkenSwift.
I wish I had paid attention to my timing advance on the SG. I seem to recall it hovered around 30 degrees at 80 km/h cruising, light load. I was seeing 10 just now. But I can't be sure. Unfortunately, I can't check it with the usual method because I have no timing light.
I'll try the regulator test with the key on/off trick. If I just cycle the pump half a dozen times using the key, by that logic it should flood the intake and make the car harder to start. We'll see.
Also, is got tons of acceleration at low RPM. No surprise there.
My Geo had a recall - seems the MAP sensor had a dip in the hose going to it and would clog with water vapor and freeze in the winter. The fix was a vent bypass orifice that leaked air throught the hose and in effect lowered the vacuum to the MAP sensor which in turn richened the fuel mixture and lowered the gas mileage. I closed off the opening in it a little extra. During that time the Geo ran rich and the MAP sensor that had failed I had before that really dropped the MPG and it ran lousy - maybe you killed the MAP sensor. Also the pressure is regulated by a return to tank bleeder - make sure it is working.
Thanks guys, it's fixed. JanGeo - you win the prize for being closest.
I should have figured this out last night when I saw the the MAP value of 14.8 PSI at all times. 14.8 PSI is close to standard air pressure. Normally the engine would only see a value that high either at WOT - or - if there's a vacuum leak.
Turned out to be a big split in one end of the MAP vacuum line where I had spliced in a T-connector for my cruise control. Trimmed off the bad end, reconnected it, and it's running normally again.
Now I understand why I didn't get a CEL: the MAP sensor wasn't bad, it was just merrily reporting very high pressure, and the ECU was responding the way it was programmed to: by going into open loop and dumping in more fuel, as if the car was at WOT.
Now, if the ECU was comparing TPS to MAP, it would have figured out that something was wrong, but I guess it doesn't do that comparison.
Anyhoo... thanks again for the feedback everybody.
At least it wasn't anything serious. Basically you caused the problem yourself.
I made a hole in my air hose and after I removed the nitrous I had to tape it with duct tape. It worked horrible. I found a dealer that sold a brand new piece and it was updated. After I installed it I gained some low end torque.