P0331 Knock Sensor Diagnostic
#21
09-29-2015, 10:30 PM
So I finished installing new plugs wires and front O2 sensors. Not sure how I did it but was able to slowly and patiently replace the sensor and even clipped it back in place without removing the coils. I was literally flat on my belly lying on the engine block.
Took it for a test drive and checked fuel trim and sensor voltage and fuel trim levels definitely back in check. LTFT is now sitting at -6% flat line with STFT fluctuating +/- 3%. This appears to be within acceptable range based a few articles I read about interpreting fuel trim levels...I"m also comparing this to my '99 Lexus GS300 which is running much closer to 0%. I'll be doing some more tests soon but not having looked this in the past, I'm not sure what is "normal" or within acceptable range for this vehicle.
I will be driving it more this week and haven't had time to put too many miles on it to burn the current low octane tank of gas I recently put in so I'll come back after some more test runs. I'm going to hold off on giving my opinion on how I think the car performs now vs before to hopefully let the placebo effect dissipate.
Oh, forgot to mention...that issue of difficulty starting when warm...that seem to have gone away based on my my test drives today and yes, I did get the engine to full temp....I got the loaner fuel system test kit from autozone to try and test fuel pressure but I could not, for the life of me figure out how to use the adapters to fit the shrader valve on this vehicle...
Took it for a test drive and checked fuel trim and sensor voltage and fuel trim levels definitely back in check. LTFT is now sitting at -6% flat line with STFT fluctuating +/- 3%. This appears to be within acceptable range based a few articles I read about interpreting fuel trim levels...I"m also comparing this to my '99 Lexus GS300 which is running much closer to 0%. I'll be doing some more tests soon but not having looked this in the past, I'm not sure what is "normal" or within acceptable range for this vehicle.
I will be driving it more this week and haven't had time to put too many miles on it to burn the current low octane tank of gas I recently put in so I'll come back after some more test runs. I'm going to hold off on giving my opinion on how I think the car performs now vs before to hopefully let the placebo effect dissipate.
Oh, forgot to mention...that issue of difficulty starting when warm...that seem to have gone away based on my my test drives today and yes, I did get the engine to full temp....I got the loaner fuel system test kit from autozone to try and test fuel pressure but I could not, for the life of me figure out how to use the adapters to fit the shrader valve on this vehicle...
#23
10-06-2015, 09:24 AM
I want to give an update and close out this thread as I will start another thread on my other issues.
Believe it or not, I've put over 1k miles since I replaced the O2 sensors and cables and ran about 3 higher octane gas through the engine. I did monitor all the sensors for the entire trip and interestingly the fuel trim levels improved over the course of the trip and is now the LTFT is a steady -0.8% with STFT +/-3%. Overall, the car "appears" to run a bit smoother with some improvements in the mountain passes....no scientific measurements here so I'll leave it at that but overall, happy with the new parts as recommended.
Thanks all and see you on my next thread.
Believe it or not, I've put over 1k miles since I replaced the O2 sensors and cables and ran about 3 higher octane gas through the engine. I did monitor all the sensors for the entire trip and interestingly the fuel trim levels improved over the course of the trip and is now the LTFT is a steady -0.8% with STFT +/-3%. Overall, the car "appears" to run a bit smoother with some improvements in the mountain passes....no scientific measurements here so I'll leave it at that but overall, happy with the new parts as recommended.
Thanks all and see you on my next thread.
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