kford1040

All,

I am new here and need help with a topic that i know has sort of been beaten to death regarding the 0171 error code. It is the ONLY error code that trips my CEL and with no understanding on my part will at some point prevent overdrive. It could be after the first time I brake driving the car or 20 miles and 30 minutes into the drive. It doesn't require clearing the CEL just shutting the car off for a minute or 2. A long stop light works. Then I can usually resume my trip to work. Not finding any vacuum leaks (checked today) and had and Oxygen sensor replaced earlier this year but I am a little unsure of my understanding of the difference between O2 sensors vs A/F sensors and their locations.

I did a drive check test on everything the scanner would check and today was the only time I was able to get the EVAP to complete. I drive up to an hour to work (30 miles) and going 5 miles with the car sitting and idling in the cold it completed today so I have no ideas and don't have the resources to just blindly replace parts.
Below are some snapshots of readings I got at idle and driving -any input - direction would be great.

Thanks in advance
Kimberly

At Idle
ST FTRM1 % 1.6
LT FTRM1 % -4.7
ST FTRM2 % 0
LT FTRM2 % -.8

ST FTRM1 % 0.8
LT FTRM1 % -3.9
ST FTRM2 % 3.9
LT FTRM2 % 0.8

Driving with error
0171
48 mph rpm 3153
ST FTRM1 % 0.8
LT FTRM1 % 39.1
ST FTRM2 % 2.3
LT FTRM2 % 38.3

O2s12 V .270
O2S11 V 3.215
eq ratio11.979
eq ratio21 .987
O2s21 3.547

0171 error at
35 rpm 1775
ST FTRM1 % 3.9
LT FTRM1 % 50.8
ST FTRM2 % 0
missed screenshot of last number

Sturds

I'm not sure about the light being intermittent it could be a loose connector or a faulty sensor that could be getting jarred and cause it to work or by shutting off the engine it could mess with the sensor, I'm not sure about the sensor levels but I can check mine out and get back with you on wether they are anywhere near the correct values. If you need a write up on the sensor locations here is one that was posted before. https://www.clublexus.com/forums/rx-...af-sensor.html

artbuc

Pretty sure you will throw P0171 when total short and long term fuel trim exceeds 35%. Since you don't have a fuel trim issue at idle when you have max intake manifold vacuum, I think you can safely rule out vacuum leaks. If you have read the many posts on this subject, you know that your A/F sensors are probably not the problem since you are not throwing any A/F sensor codes. Does your car perform badly (hesitate, sputter) when you accelerate hard from say 40 to 50 mph? If not, you can probably rule out fuel supply issues. Clean your MAF well (search here and other places for excellent DIY help). If this doesn't work, replace your MAF sensor.

Warning: I am not a mechanic and I did not sleep at the Holiday Inn last night.

kford1040

Thanks for the link on the locations.

The car sounds fine in general the only - she idles fine but if you hit the accelerator to rev the engine or while driving there is definitely a hesitation.

I will try cleaning the MAF sensor again - I couldn't actually get it unplugged the first time and was nervous about it.

I also need to change my spark plugs and am a bit nervous about that since my other car met the bumper of another on my way to work last week and rendered her undriveable . So I have no way to 'run' go get something if I don't do it right the first time.

I'll finish my coffee and go try to clean the MAF sensor this morning and see what happens.

Kimberly

artbuc

Sounds like a fuel delivery issue. Maybe a bad regulator, fouled injectors or fuel pump going bad.

PS Do you know for sure which MAF wires to clean and are you using MAF safe cleaner?

Sturds

Like the others said it could be fuel delivery I would recomend quicksilver quicklean its a product made for outboard boat engines use a little extra than what is says its a liquid you put in the fuel tank it will clean out all your injectors and any other fuel system components. Also there is a product called Powertune by OMC it is also for outboard engines and is sprayed into the carbeurator, it wont hurt your engine but when I use it I can tell a huge difference in the performance especially when using power tune and quicklean. For the powertune just loosen the air boot right before the MAF then insert the straw until it is past the MAF sensor so it doesn't actually go onto the MAF the engine will rev up just spray it in bursts to control the speed without letting it overrev. If it stalls right away try and idle up the engine before spraying it in.