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my 99 toyota 4runners check engine light has been a problem for months. we were told it needed an a\f ratio sensor so we replaced it. within a couple of weeks the light was on again. at first would go on and off now on all the time. had it back to mech. and got code po172. they cleaned fuel system and told us to drive to see if light comes back on and it was on again before i even
got home. it seems to idle low when stopped now and then and has stalled a few times. any suggestions would help.
Answer -
Before I can help with this I need to know if it is a 4 or 6 cylinder engine but basically this code indicates a rich air fuel mixture, was the original trouble code the same when the A/F sensor was replaced?
it is a 6 cylinder 3.4l. the first mechanic just told us the code was bank one when the a\f sensor was replaced.
thanks again
AnswerPossibly a mass air flow meter problem, it's located on the intake pipe just behind the air filter, it can removed and cleaned with electronic or circuit board cleaner, also replace the air filter.
There are small platinum wires in the MAF that get coated with dirt, these wires measure the air flow through the intake pipe and send a signal to the computer, if they get dirty the computer will receive a false signal and turn the check engine light on, the solution is to spray the electronic cleaner into the inside of the sensor to clean the sensor wires.
