P0171 with Landtank's MAF

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

BAD MAF

these pics are with the bad maf supplied with the housing.

You'll notice that the fuel trims are beyond the point of error of 20% and they are positive so that means the system is adding fuel to the baser calculations.

You'll notice that the wide band is indicating a proper AFR even though the system is in error and exceeding the acceptable range.

slee busting 007.webp


slee busting 008.webp
 
BAD MAF screwed

At this point I wanted to further cause problems for the system by introducing an air leak which would introduce more un-metered air into the system

I did this by jamming a screw driver into the air hose next to the MAF

You'll notice that the Short Term Fuel Trim reacted by adding 10% to the furl trim and we still have an acceptable AF%R reading from the wideband sensor

slee busting 010.webp


slee busting 009.webp


slee busting 012.webp
 
Rick,

I can't read the screens but this is what is expected no?

Larger MAF housing bore means more air. Fuel trim has to increase to keep AFR in the same range. Once fuel trim increases high enough to trip the CEL it doesn't mean you are running a lean AFR, it means your running "leaner" than expected and the fuel trims have to be bumped way up. The CEL basically means check your engine for unmetered air.
 
As you can see at no time was the AFR in a dangerous area concerning the engine running LEAN.

The issue with the sensor was actually quite simple. Somebody installed it incorrectly and pinched the O-ring between the housing and the sensors base. This cause the sensor to be come deformed and it no longer would sit flat causing it to not read the air flow correctly.

Attached is a pic of the o-ring and were it got pinched. Being that it was bought used it was likely already identified as having an issue and replaced for it.

The P0171 code does not indicate the O2 levels are in a dangerous lean state. It is merely indicating that the ECU is compensating outside what it feels is an acceptable range and someone needs to figure out why. In this case the provided sensor was bad.

maf2 001.webp
 
Ok now if the MAF sensor was bad, and you weren't actually getting as much air as it was reporting, the AFR should have read much richer, since the computer was still adding more fuel per the LTFT. Do both sensors report the same voltage at say idle and 3000rpm's?

**Edited you were posting that the sensor was distorted while I was typing this.
 
Couple of questions, and please don't take this the wrong way and get defensive.

1. Was the sensor letting in unmetered air since it was not sealing properly, or is it because of the alignment of the sensor that it was off?

2. Were all the test done at idle?

3. You mention "The P0171 code does not indicate the O2 levels are in a dangerous lean state."
Did you log any fuel trims while driving to be comfortable with the above statement at higher air flows and also at WOT?

4. Did you have access to the freeze frame data to see when the actual code was triggered?
 
sleeoffroad said:
1. Was the sensor letting in unmetered air since it was not sealing properly, or is it because of the alignment of the sensor that it was off?
Click to expand...

In my opinion it was more of an alignment issue. The sensor stick portion looked noticeably out of place and twisted slightly. But the body of the sensor is also deformed so there could be internal damage as well. Any unmetered air that might get by the bad o-ring would not be anywhere near that of the screw driver I stuck in there.

sleeoffroad said:
2. Were all the test done at idle?
Click to expand...

Some of those shots are of driving. But prior to today I was actually driving around with 3 screw drivers stuck in the hose trying to create the condition with a good sensor. At that time my FT% was over 50% and never saw anything other than 14.7 except at wide open throttle it richened some.

sleeoffroad said:
3. You mention "The P0171 code does not indicate the O2 levels are in a dangerous lean state."

Did you log any fuel trims while driving to be comfortable with the above statement at higher air flows and also at WOT?
Click to expand...

Again if you look at the driving shots of the good sensor you will see that the fuel trims were out of range as the LTFT are still present from the bad sensor. And again the fueling was fine based on the wideband.

sleeoffroad said:
4. Did you have access to the freeze frame data to see when the actual code was triggered?
Click to expand...

I'm not sure if I have that ability or not. It seems to be a 2 trip trigger and only while driving. I originally drove around for about 15 minutes and on the second trip it triggered about 5 minutes into the drive.

The gear is still in place on my truck and I'm sure that sensor is still bad so I can do my best to provide what ever info people might want to see. But it kind of hard driving, watching the road, watching the meters, dealing with a laptop on battery power going into saving mode and taking pictures.

I must of had 30 bad pics from when I was driving around because it was a blind point and shoot and not everything was in frame.
 
landtank said:
In my opinion it was more of an alignment issue. The sensor stick portion looked noticeably out of place and twisted slightly. But the body of the sensor is also deformed so there could be internal damage as well. Any unmetered air that might get by the bad o-ring would not be anywhere near that of the screw driver I stuck in there.



Some of those shots are of driving. But prior to today I was actually driving around with 3 screw drivers stuck in the hose trying to create the condition with a good sensor. At that time my FT% was over 50% and never saw anything other than 14.7 except at wide open throttle it richened some.



Again if you look at the driving shots of the good sensor you will see that the fuel trims were out of range as the LTFT are still present from the bad sensor. And again the fueling was fine based on the wideband.



I'm not sure if I have that ability or not. It seems to be a 2 trip trigger and only while driving. I originally drove around for about 15 minutes and on the second trip it triggered about 5 minutes into the drive.

The gear is still in place on my truck and I'm sure that sensor is still bad so I can do my best to provide what ever info people might want to see. But it kind of hard driving, watching the road, watching the meters, dealing with a laptop on battery power going into saving mode and taking pictures.

I must of had 30 bad pics from when I was driving around because it was a blind point and shoot and not everything was in frame.
Click to expand...

Sounds like you need a ride along :hillbilly:
 
Rick,

Maybe that camera has a video function that would run long enough for this application. After the duct tape mount, of course... :) If so, you could take mind and eye off the camera at least.
 
Joey's FleaBay sensor was not such a good deal after all.

I can appreciate the difficulty of trying to drive responsibility and take pictures at the same time, and it was nice to see how well the ECU does at maintaining good AFR when presented with a bad sensor and unmetered air. Well done.
 
1973Guppie said:
Makes sense why my truck runs just fine with the landtank maf in now. Can't say I understand all this stuff but will there still be a necessary fix for the GEN1 maf's?
Click to expand...

initially I was concerned about the elevated FT% during idle and possibly getting a P0171 code.

As it turns out the ECU doesn't care what's happening during idle and only monitors the Fuel trims while driving. During those times the fuel trim on a GENI are well within the acceptable range.

I think a GENIII housing will slightly perform better but it's up to the end user as far as if it's worth it.
 
You must log in or register to reply here.

Share this page

Back
Top Bottom