1998 Lexus GS400 - P0172 - Runs Rich
#19
Maintenance Moderator
iTrader: (2)
Unfortunately, it will... it would have to be pretty severely restricted, but it will most definitely cause this issue. It doesn't seem like it should, but it does. There are many cases documented in Identifix in which a restriction to the air intake system, before the MAF that caused system rich conditions... One of the reasons is throttle tip in fuel. Give the car some throttle, the ECU adds fuel ahead of time because it anticipates the added fuel need based on throttle position change, but, if the airflow doesn't keep up with what it was programmed for, then that extra fuel creates a rich condition...
#21
Lexus Test Driver
iTrader: (22)
Unfortunately, it will... it would have to be pretty severely restricted, but it will most definitely cause this issue. It doesn't seem like it should, but it does. There are many cases documented in Identifix in which a restriction to the air intake system, before the MAF that caused system rich conditions... One of the reasons is throttle tip in fuel. Give the car some throttle, the ECU adds fuel ahead of time because it anticipates the added fuel need based on throttle position change, but, if the airflow doesn't keep up with what it was programmed for, then that extra fuel creates a rich condition...
Last edited by GS4_Fiend; 06-22-13 at 06:25 PM.
#22
Maintenance Moderator
iTrader: (2)
On a MAF L-JET vehicle, if you got a plugged air filter, the PCM knows to compensate the fuel mixture. Therefore, you won't have a rich condition. Plus, he got a code for P0172. So, that's only one bank. In addition, the PCM watches the voltage on the MAF sensor, if the voltage is low, the PCM is not gonna be leaning the car out..It should increase pulse width on the injectors instead, which would be a lean condition not rice. Also it would only make sense if it was on a D-JET system because the MAP sensor senses high pressure. For one bank to be rich only. the possibilities could be plugged cat or bad oxygen sensor.
Again, you can assume what will or won't fix it, I'm just saying that in past similar issues, restricted intakes have caused this exact same issue... I don't have the proof for you in front of me, but monday at work, I will show you where it was documented that a severely restricted air filter caused this single code by itself on this exact same year make and model car. You can argue all you want, but sometimes issues don't always follow conventional logic. In theory, even, there is not much difference between a restricted cat and a restricted intake - as the MAF is still reading the amount of air and a restriction either place reduces airflow...
#23
Lexus Test Driver
iTrader: (22)
I didn't say that was specifically the issue, just an idea...
Again, you can assume what will or won't fix it, I'm just saying that in past similar issues, restricted intakes have caused this exact same issue... I don't have the proof for you in front of me, but monday at work, I will show you where it was documented that a severely restricted air filter caused this single code by itself on this exact same year make and model car. You can argue all you want, but sometimes issues don't always follow conventional logic. In theory, even, there is not much difference between a restricted cat and a restricted intake - as the MAF is still reading the amount of air and a restriction either place reduces airflow...
Again, you can assume what will or won't fix it, I'm just saying that in past similar issues, restricted intakes have caused this exact same issue... I don't have the proof for you in front of me, but monday at work, I will show you where it was documented that a severely restricted air filter caused this single code by itself on this exact same year make and model car. You can argue all you want, but sometimes issues don't always follow conventional logic. In theory, even, there is not much difference between a restricted cat and a restricted intake - as the MAF is still reading the amount of air and a restriction either place reduces airflow...
#24
STFT Bank 1: -3.9%
LTFT Bank 1: 0.7%
STFT Bank 2: -3.1%
LTFT Bank 1: 0.0%
Bank 1 Sensor 1 O2S Output: 0.040V
Bank 1 Sensor 1 STFT: 0.0%
Bank 1 Sensor 2 O2S Output: 0.045V
Bank 1 Sensor 2 STFT: 99.0%
Bank 2 Sensor 1 O2S Output: 0.805V
Bank 2 Sensor 1 STFT: 0.7%
Bank 2 Sensor 2 O2S Output: 0.115V
Bank 2 Sensor 2 STFT: 99.0%
#25
Maintenance Moderator
iTrader: (2)
I hate to create such a controversy, but yes the results from the first test were indeed positive. I just went out and retested the car and here is what I received. Note that the car isn't fully warmed up.
STFT Bank 1: -3.9%
LTFT Bank 1: 0.7%
STFT Bank 2: -3.1%
LTFT Bank 1: 0.0%
Bank 1 Sensor 1 O2S Output: 0.040V
Bank 1 Sensor 1 STFT: 0.0%
Bank 1 Sensor 2 O2S Output: 0.045V
Bank 1 Sensor 2 STFT: 99.0%
Bank 2 Sensor 1 O2S Output: 0.805V
Bank 2 Sensor 1 STFT: 0.7%
Bank 2 Sensor 2 O2S Output: 0.115V
Bank 2 Sensor 2 STFT: 99.0%
STFT Bank 1: -3.9%
LTFT Bank 1: 0.7%
STFT Bank 2: -3.1%
LTFT Bank 1: 0.0%
Bank 1 Sensor 1 O2S Output: 0.040V
Bank 1 Sensor 1 STFT: 0.0%
Bank 1 Sensor 2 O2S Output: 0.045V
Bank 1 Sensor 2 STFT: 99.0%
Bank 2 Sensor 1 O2S Output: 0.805V
Bank 2 Sensor 1 STFT: 0.7%
Bank 2 Sensor 2 O2S Output: 0.115V
Bank 2 Sensor 2 STFT: 99.0%
#26
Lexus Test Driver
iTrader: (22)
I hate to create such a controversy, but yes the results from the first test were indeed positive. I just went out and retested the car and here is what I received. Note that the car isn't fully warmed up.
STFT Bank 1: -3.9%
LTFT Bank 1: 0.7%
STFT Bank 2: -3.1%
LTFT Bank 1: 0.0%
Bank 1 Sensor 1 O2S Output: 0.040V
Bank 1 Sensor 1 STFT: 0.0%
Bank 1 Sensor 2 O2S Output: 0.045V
Bank 1 Sensor 2 STFT: 99.0%
Bank 2 Sensor 1 O2S Output: 0.805V
Bank 2 Sensor 1 STFT: 0.7%
Bank 2 Sensor 2 O2S Output: 0.115V
Bank 2 Sensor 2 STFT: 99.0%
STFT Bank 1: -3.9%
LTFT Bank 1: 0.7%
STFT Bank 2: -3.1%
LTFT Bank 1: 0.0%
Bank 1 Sensor 1 O2S Output: 0.040V
Bank 1 Sensor 1 STFT: 0.0%
Bank 1 Sensor 2 O2S Output: 0.045V
Bank 1 Sensor 2 STFT: 99.0%
Bank 2 Sensor 1 O2S Output: 0.805V
Bank 2 Sensor 1 STFT: 0.7%
Bank 2 Sensor 2 O2S Output: 0.115V
Bank 2 Sensor 2 STFT: 99.0%