jimboN

My 1999 RX 300 with 320k came up with code P0171. I cleaned the Mass Air Flow Sensor with no help so replaced it. Code came back after 200 mile trip. I'm thinking I have never replaced the gas filter, could this be the problem? My dash computer says my highway mileage has gone down from 22 mpg to 12 mpg but I think its wrong because my fuel gauge doesn't agree, At 300k plus I know it could be a number of things, any suggestions?

salimshah

JimboN: You need to focus on the error code the computer is generating. If you go by hunches .. you will be ripping the whole vehicle out.

What did the auto-shop suggest that you change?
MAF -> impacts both [bank 1 and bank2].
I would look at the bank 2 oxygen sensor.

Do not buy after market sensors [my opinion]

Salim

jimboN

Since the code referenced running lean fuel bank one, I followed old posts to deduce checking MAF first. Since I do a lot of DIY and haven't been to a shop I was interested in feedback from others experiences and i don't remember saying anything about hunches.... Jim n

salimshah

JimboN:

Often my advice comes across as very dry and to the point. I never try to put any one down. I myself am not an expert.

My post was to make you rethink that MAF and working your way back to fuel is not the right way. Both of these are in the common chain ... before the bank1-bank2 split. Problem in there will impact both banks. Since your problem is only in one bank, you need to focus on that bank.

Did the auto-shop recommend changing anything? With that many miles sensors are the most likely to fail.

Salim

Salim

carguy07

Do you have any other codes?

artbuc

This is bad advice. P0171 is almost never Bank specific. Cleaning MAF was correct first step. Very unlikely it is A/F sensor without a specific A/F sensor code. Look,for vacuum leak or fuel delivery issue.

salimshah

I got my info from
https://www.autocodes.com/p0171_lexus.html

My apologies if the above info is wrong.

Salim

artbuc

Good first step. I have resolved many P0171 codes on the 1MZFE ny cleaning the MAF sensor.

jimboN

Thanks for all the suggestions. carguy07, No other codes....The vacuum leak is a possibility and I will check into that, but I think artbuc might be on to something, because when I cleared the code and filled up with premium fuel the code is gone, could have been bad fuel. After 300k I still think it would be a good idea to replace the fuel filter, Thanks again

I'm going to keep the 99 rx 300 for runs to the hardware, garden supplies and camping and canoe trips but the wife wants to buy a 2016-2017 RX 350, any comments good or bad would be appreciated. I suggested the NX but she nixed that. Jim n

maxSteel

The emissions cycle takes a while. I've been ignoring this code for a while. If I clear it out it will come back in a few days. The timing varies based on multiple factors.

jimboN

Thanks maxsteel, that makes good sense, i was thinking that when I hit the erase button. Now that it's in the end days I have neglected it somewhat.
Hey, what can i say 300 plus was a good run in my opinion. I never had a chevy or ford last that long and I have never added a quart of oil between changes, Castrol 5-30.

salimshah

That is awesome ... would that be 300K Miles.
I am glad that you have provided yet another data point that RX does not consume oil.

Salim

jimboN

Yes, 316,400 to be exact. Has never used o a quart of oil. I like to tell the story of when I hit 200,000 and the local Advanced auto ran the Casrol 5-30 on sale I bought 2 cases in anticipation of needing to add oil between changes in the future. The joke is , the only time i have every used the oil was for my lawn mower oil change. By the way how long is stored oil good for because i still have plenty?
Jim n