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P0171 - "System too Lean" Bank 1. Cleaned MAF Sensor.
1. 2002.
2. 127,050 on the clock at the time of cleaning. DTC had been triggering for several thousand miles +. Finally got my lazy ass to clean the MAF Sensor (sensing bulb).
3. There was definitely some scuz on the sensing bulb.
4. Will follow-up to this thread after multiple (say 2 or 3) fuel fill-ups.
1. DTC P0171 triggered again after less than 20 miles of driving after cleaning the MAF Sensor.
2. Poked around some, found some oil seepage aroound the PCV. Figured 127k+ on the clock, why the hell not? Let's change out the PCV.
3. Replaced PCV, Grommet and Hose, and drove around and monitored STFT & LTFT percentages. LTFT % dropped from 39.8% to 6.3%. Not bad.
4. So, is the PCV the ultimate culprit? Hard to say. I did the ol' suck-and-blow (no homo) test and it passed. But, the PCV ball float (ball float valve, ball cheengus, etc) could be sticking / sticking intermittently perhaps? Also, the PCV Grommet was brittle / dry-rotted.
5. Going to drive her some and go from there. If P0171 returns, well, then I'll dig deeper (smoke test, test Fuel Injectors, replace MAF, etc).
Last edited by GoneToYosemite!; Dec 2, 2024 at 02:40 PM.
That bulb isn't the actual MAF sensor, I think it might be an intake air temp sensor. The ECU probably uses that for fine tuning the fuel calculation.
The MAF sensor is a fine bare metal wire well hidden in the center plastic like tube structure, which guides a portion of the air going past over the wire. The wire is heated and the passing air cools it down. The amount of cooling is how it reads the mass of air going by.
This wire will become 'insulated' if it gets a coating of dust or oil, then the cooling effect of the air going by is thrown off, and the MAF reading starts to become incorrect.
Be *very* careful with the wire, it's quite fragile. That's why it's hidden off inside a tube like that.
That bulb isn't the actual MAF sensor, I think it might be an intake air temp sensor. The ECU probably uses that for fine tuning the fuel calculation.
The MAF sensor is a fine bare metal wire well hidden in the center plastic like tube structure, which guides a portion of the air going past over the wire. The wire is heated and the passing air cools it down. The amount of cooling is how it reads the mass of air going by.
This wire will become 'insulated' if it gets a coating of dust or oil, then the cooling effect of the air going by is thrown off, and the MAF reading starts to become incorrect.
Be *very* careful with the wire, it's quite fragile. That's why it's hidden off inside a tube like that.
Jomoka, you are correct.
Some confusion there on my part (probably brought on by the medicinal whiskey), but I did mean to mention (and post some pics) of those two wires / sensing elements / "hot-wire" that reside inside that "tube structrure" / tower-portion of the MAF Sensor, but, pics were blurry (or my vision...see aforeentioned whiskey reference) and I just got on with the post.
Nov 18, 2024 | 05:25 AM
