A/F question

[Beagle(4)Runner]

I searched but was unable to find a clear answer. My 99 T4R CEL has been on for a while (2 years), code was P1133. Mechanic said would only affect mileage so I ignored it, mileage has been 17-19 which appears to be average. Last week, started getting about 120 miles to a tank. I cleared the codes and once CEL came back on, took it to advanced auto. Codes this time were P0171 Bank 1 system to lean and P1133 Air/ Fuel Sensor Malfunction. I have a CA Emission model (2 cat converters). My question is, does P1133 mean the front O2 sensor is bad or what? What does P0171 mean? In reading other posts, I am going to clean my MAF also as I have 192000 miles and I am pretty sure it has never been changed or cleaned. I've had it for the last 17000. Any other suggestions of things need to do. Plugs and wires changed about 20,000 miles ago.

 

[Stick Figure]

http://www.ncttora.com/fsm/1996/SIL...2rmsour/2002/024runne/di/eg5vzfe/cip0171p.pdf

and

http://www.ncttora.com/fsm/1996/SIL...02rmsour/2002/024runne/di/eg5vzfe/cip1133.pdf

that should get you started on understanding why the codes could be on and where to start troubleshooting.

 

[TheDurk]

P0171 is "System Too Lean". It means your ECM has your fuel trim set over limit to the RICH side. So it could be a sensor problem, or some other issue is keeping you with too little F in your A/F ratio (or too much A). The '99 FSM says to address p0171 before you do P1133. The P0171 causes are many:

-air induction (too much A)
-injector injection (too little F)
-MAF and ECT (sensor issue)
-spark and ignition(combustion not happening, so O2 is high, just as in lean A/F)
-fuel pressure(too little F)
-exhaust leak (fools sensor)
-o2 sensor isssue

Losing power--just went to UPS, so posting incomplete (snow storm.) I'll finish later....

 

[Beagle(4)Runner]

Thanks for the technical info. Beside cleaning the MAF sensor, as I am not a mechanic, what would be the other options to try before taking it to my mechanic. I did have some exhaust leaks and once I fixed them is when it started using excessive fuel. I would think if it was a combustion issue, it would idle rough or have a miss which it does not. The only symptoms I am having is the increase in fuel consumption and strong smelling exhaust, which doesn't seem as strong since I reset the lights. Suggestions please!

 

[Beagle(4)Runner]

I cleaned the MAF, pretty simple. My wife drove it today, check engine light came on and is still using excessive fuel. As previously stated, I am not a mechanic and have only the basic tools, an ideas of what I could try next before I take it to my mechanic. I did not have a chance to get it re-scanned but I am guessing same codes will come up.

 

[TheDurk]

Sorry--turns out I lost power for three days after my earlier post. Got pretty cold and boring in my house. (52°F). I would consider injectors unlikely since you are using excess fuel. If you have checked for intake and exhaust leaks, I would next hook up a live scanner (different from a code reader) and verify that O2 sensor, considering the p0133 codes. Or you could take a chance and just change it if it is due anyway (90K+).