Poor milage and P0172 code

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...

[C a v l r Z]

wow! did you get that fuel out of there???



i have no clue of how that can hurt... but E80 is a mixture of 80% ethanol and 20% gasoline, and is generally a higher ethanol fuel mixture.... and it's a higher octane rating than what the cavalier is made to handle... i know E85 has a 105 octane rating.... the cavalier is made for the lower octane gas :lol:

It was in Minnesota. Then the next day this started...

[SHOoff]

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.

That gas has been gone for awhile...she filled it up on a road trip and i was asleep...I knew there was a reason i usually do all the driving...anyway...

Thats about were i'm at now...I've cleared the code twice...once by disconnecting the battery(no access to a scaner) and the light came back once by scanner(about a week ago) and it hasn't come back yet...The first time there may still have been alittle left in the system.

I guess i'll give it another week...the mileage is still kinda shitty though...I'm on i think the 3rd tank since that e85 so it should be completely flushed by now...

[SHOoff]

If it pops back up again, I'd just change the O2 sensor. It's the front one. The car has 2, one before and one after the cat. converter. The problem is the one BEFORE the cat. Which is also WAY less expensive.

[misnblu]

Your long term fuel trim went way out of whack and the ECU tryed to compensate for the overly rich reading.
A scan gauge would be nice to determine what your short and long trim fuel readings are and can make an assessment then on what to do.

Like SHOoff said, replace the O2 sensor especially if it hasn't been changed in years.
It may be a part of the problem in that when they get weak, fuel trims can go deep into the negative (overly rich) because the O2 can't compensate fast enough to keep it in stoich or lambdum 14.7. That's the whole purpose of the O2 sensor and that's to keep emissions down for the regs.

Good luck with it and keep us informed on what happens.

Misnblu

I'm keeping an eye on it...Problem is i never drive that car and the wife doesn't really pay attention to much of anything so...

disconnecting the battery should have cleared any adapted fuel trim, shouldn't it?

[SHOoff]

Yeah, but you gotta leave it unhooked for a while. Like 30 mins. I'd restart the engine while it's completely cooled down too. Cuz then it has to start fresh off all the tables. Then warm up and get into closed loop before it starts to re-learn the fuel trims.

thanks.