CEL Code PO171 (Bank 1) System Too Lean

[EricHaven]

Hello,

I just bought a used 2000 Chevy Prizm, which I am told is the same as the Corolla. About a month after I bought the car, the CEL came on. The scope I rented from the auto parts store read the code as PO171 (Bank 1) System Too Lean. I was advised that there was a tiny chance it was the catalytic converter, except that the car has no power issues whatsoever, and it does not stink when running, like a clogged cat would suggest. I was also told that it might simply be a clogged MAF sensor, and that a quick hit on the wires with carb cleaner might do the trick. Of course, the suggestion of the O2 sensor itself came up, but the guy at the auto store didn't think so.

The only problem I have noticed is that after I drive it for a while, then stop and park for a bit, then get back in, it seems to have trouble turning over again. Usually it takes me two or three tries to get it lit again, but after that, no problems running at all. It comes up to full power in no time, and literally flies down the highway. I have taken in all the way up to 90 MPH (not for too long, obviously, to avoid an accident and/or ticket), and it does so with no problem or hesitation at all.

In ever respect, the car seems to run perfectly, with no issues other than the starting when warm thing.

Other than that, I really love this car, and I am hoping it will be an easy fix.

Any suggestions?

Thanks!

[buci]

There is a good chance you have a vacuum leak somewhere, the system is taking more air than it's supossed too.Check the vacuum lines and the big intake pipe from the air filter to throtle body. Also listen to the engine idling if you hear a hissing sound.

[Crowbar911]

I was getting the same code on my 01 corolla. I didnt have any problems other than some small MPG loss.

Turned out to be a bad MAF. Once I replaced it, it never came back.

You may be differnt because of the starting issue.

Also, I never understood how the code can be the cat because from what I understand, is that the o2 sensor BEFORE the cat is giving the code, Leaving everything downstream out of the equation.

[Bitter]

clean MAF, go from there.

[EricHaven]

Thanks Guys!

I went down and got a can of the CRC MAF Sensor cleaner, and took out the MAF and cleaned it thoroughly. I also pulled the negative battery cable to clear the CEL while I let everything dry out. Half an hour later, I put it all together, and test drove it for about 50 miles. I have to say that car seems to run even smoother than before, and the CEL has not come back on. I still have my fingers crossed, but so far, so good!

Thanks again Everyone!

[teppista881]

I do this at least once a year if not more. You'll get your money's worth out of that cleaner if you keep the car.

[EricHaven]

I just wanted to give a quick update. Last week, I drove my car down to California from my home here in Washington and back. I logged 2100 miles in total, and not once did the CEL come back on. I also noticed that the start-up issue I had went completely away, and now my car fires right up no matter if I have driven it or not.

Thanks again Everyone!