Im having a problem that fixed itself 2 times in the past, but recently decieded to stick around. To start the car will either idle too high or to low & die (in closed loop). The 02 sensor reads 0 Ox counts and continuos 934mv. Therefore the engine stays running rich. It is undriveable because it puts/bucks wildly and smooths out for moments when boost is applied. At lights you either have to stand on the brakes or pat the gas to keep it running. I get no error codes except an O2 malfunction that went away. I changed the O2 sensor anyway and it still only reads 934mv. Now I pulled the chip which was a homemade stock chip and noticed corrosion on the 1st 2 bottom pins. I put a mystery chip in instead (came with the car), but the car does the exact same thing. Could the corrosion have gotten into the pin holders on the ECM blocking a signal, could this be the problem? (sorry about the length)
A buddy had the same problem. We first replaced the 02 and still had the problem. Then we discovered he had a bad MAF sensor and that fixed it. Be careful buying those "refurbished" units...I would buy a used GM unit from Ebay. I got one for $35.00.
I also put my friends MAF sensor, and it didn't change anything. Maybe his was bad as well.