It was from a 1992 Bonneville SSEi, so it should be a good fit. ACDelco site says that even a 92 SSE MAF sensor will fit (SE won't).

I think I had the battery off overnight when I installed the new sensor. Regardless, I checked and there weren't any stored codes. I'll take it off again for 30 minutes just to be sure.

I took off the battery cable for half an hour, and same problem. Drives fine, but if shut off and started up a little later, won't start until I read the codes again. One other thing I noticed is that if I shut off the car after driving, and start it up immediately and then shut it off again, it will later start up fine. Only code 34 is coming up.

I am at my wit'* end. Anybody has any ideas???

OK, you have a diagnostic tool? What g/* readings are you getting at idle and at WOT? Have you checked for any leaks around the throttle body, or is your air intake filter or intake plugged?

Or the Maf screen in the TB?

On the way over to work this morning, the car died while driving! Now, code 21 (TP voltage too high) is coming up. I think I will get it towed to the mechanic now.

My air filter and intake are fine. I don't have a diagnostic tool. My MAF screen is a bit cracked up, but would that cause a problem? I don't know how to check for leaks around the TB.

OK, three days at the garage, and this is what they figured out. I need a new TP sensor. Fine. That should take care of the code 21 (TP voltage too high).

For the MAF sensor code (34), they said that there seems to be vacuum leak where the vacuum actuator (I think that is what it is called - please see the attached pic with the part circled in BLUE) meets the supercharger (it is on the underside). It looks like a lever.

http://f1.pg.photos.yahoo.com/ph/fai...18.jpg&.view=t

Is this what the circled part is called? Can I take it apart and somehow fix the vacuum leak? The guy figured it out by spraying some WD-40 in there and the car starts choking. The idle is a bit high also at 1100 RPM.

You think it is safe to drive the car back home like this (about 10 miles) so I can work on it?

Thanks for your help, guys.

It looks like the problem has been solved finally! :?

The mechanic changed the TP sensor and I brought the car home. The next day, I took apart the TB for a thorough cleaning (it was very dirty and the butterfly was a bit sticky). I also changed the TB gasket. Where the mechanic thought was the vacuum leak (where the boost control solenoid meets supercharger), I stuffed an O-ring from outside just to be safe.

Now the car is running better than before. Good idle, good pickup, good boost. Even the shudder problem that I previously thought was related to the transmission is gone completely!

I don't know if it was the dirty TB (I would think so), but I certainly would be cleaning it every 50,000 km from now on.