P0171 Engine Code on '01 Corolla

[automaton]

Hi all, my first post, so forgive me if I screw up or commit some crude breach of decorum. Anyways, down to business--a friend of mine has a 2001 Corolla with about 65K miles showing a P0171. Judging from threads I found here, it seems the going cause of this code is the MAF sensor. I've cleaned the sensor elements with electrical contact cleaner and cleared the alarm, but it came back after only a few miles driven. We tried all the ohmmeter tests shown in the Haynes manual for the MAF, and they all looked OK. So how about it Corolla Cognoscenti, do you think we should gamble $69.95 (Advance Auto) that it's a sneaky problem with the MAF that we couldn't find, or look for something else?

automaton

[Maxpayne124]

from what i know about p0171, it could be more than one possibility of problems:

1)MAF sensor (already covered)
2)running lean due to aftermarket intake, leak in intake man, leak in exhaust

hope this helps

[automaton]

Originally Posted by Maxpayne124

from what i know about p0171, it could be more than one possibility of problems:

1)MAF sensor (already covered)
2)running lean due to aftermarket intake, leak in intake man, leak in exhaust

hope this helps

. . . It has the stock intake. I forgot to mention in the initial post, but we tried changing the intake manifold gasket early on because it's cheap, and on this car, easy. I can't hear any obvious leaks in any of the hoses etc., though I don't claim to be good with EFI stuff. We went ahead and ordered a MAF late yesterday, but I'll try your suggestion of looking for an exhaust leak before installing it--guess they might take it back if we end up not using it. When (if) we get it figured out, I'll post the outcome so other users with the same problem can use the info.

automaton

[automaton]

Ok, I believe we have this one fixed (the guy's been commuting in it for a few days and the code hasn't returned) so I'll post the resolution in case anyone with the same problem might be doing thread searches. Things done since last post were:

1. Checked for exhaust leaks per TN user Maxpayne124's suggestion. Don't know why this one didn't occur to me but anyway, we didn't find anything. So, we proceeded with . . .

2. Changed MAF sensor (remanufactured unit from Advance Auto Parts, $69.95, $50.00 core charge).

As I said in a previous post, we had tried cleaning the sensor elements with contact cleaner, and had done all the tests with an ohmmeter shown in the Haynes manual, and the existing sensor showed good. I was nervous that we might have thrown away his money, but the replacement sensor did the trick. Apparently, there can be something wrong with them that's hard to home-diagnose. So there you have it TN users, another P0171 code down to the MAF sensor.

HTH; automaton