Originally Posted by 8616v
I've got a 2003 caviler(wifes) that has recently started throwing P0172 (sys 1 bank 1 too rich) and getting very poor milage. I originally set out to clean the MAF and clear the code only to get things apart and discover that the caviler doesn't run a MAF system. So i'm now kind of at a loss...
One potentially relevent piece of information...she put a tank of E80 in because she doesn't know any better...I know 1 tank shouldn't really hurt anything but...I know really don't know either...
Were is a good place to start diagnosing this problem?
I've searched around here and there doesn't seem to be anything that helps. Thanks in advance...
Ok.... E80 is 80% Ethanol 20% gasoline. If you run one tank it's likely not to hurt anything. GM and the gas company's will most likely both tell you this. Also, the E80 (or 85 or whatever it may be) needs to be a LOT more rich. E85 should be running at 9.6:1 AFR. It has nothing to do with the octane rating.
Bank 1 Sensor 1 is an O2 sensor. Not the MAF (j-bodies are a speed density system, so they only measure the air temp with the IAT sensor, but that's not the code that's being thrown in this case)
I would first, clear the code (any local auto parts store can probably scan it and clear it for you) And then see if it comes back. What i'm thinking may have happened is that with the Ethanol in there, it may have started to detonate (since your ECU is trying to get a 14.7:1 afr and as mentioned, e85 should be at about 9.6) from running too lean. It probably started to retard the timing to correct the knock, and when it didnt work it started to dump more fuel, until it started getting really rich. It may be running rich, simply because it's trying to.
I'd say, get that gas out of there (burn it out if you have to, it should go quicker than gas... and sounds like in your case... much quicker) then refill with regular ol 87 octane stuff like it should have, and clear the code... and see if it comes back. If it does, it's probably the O2 sensor has gone bad.