2000 toyota avalon v6 has codes p0301 p0302 and p0171

SOURCE: 1998 FORD EXPLORER SPORT 4X2 4.0 OHV

I have 98 explorer im getting same codes ive worked on cars all my life I havent replaced anything but my fuel filter so far on the explorer and that wasnt it.I know people tell you to replace all that other stuff,but if you know cars and how the stuff works thats on a car then you can fix anything with out people telling you;you need to buy this and then this and there just fishing when the dont know there as* and whole in the ground.Im going to replace my lower and upper intake seals like he says above.At least theres one more smart one out there and not someone that thinks they know it all like people that work in the parts places and some dealers.

SOURCE: PO171 error code System too lean bank 1

Here are some possible causes, I would start with anything related to replacing the intake.

Air leaks in intake manifold, exhaust pipes or exhaust manifold
Fuel control sensor is out of calibration
Low fuel pressure (fuel filter clogged, pressure regulator failure)
One or more injectors restricted or pressure regulator has failed
O2 sensors contaminated, deteriorated or has failed
Vacuum hose is disconnected, broken, leaking or loose

mike loshbough

• 1011 Answers
• Posted on Nov 10, 2009

SOURCE: Getting a code of misfire on cylinder 2, Bank 1 and lean code

Higher compression usually only happens when extra oil is introduced in to the cylinder.Your rings seem good due to the good compression .If there is a worn valve guide in that cylinder this would allow oil to seep into the cylinder .Also allowing for extra rocker arm movement which could be your chirping noise and cause a rough idle.The lean code sounds like something different like the is still a vacuum leak.It sounds like you know cars well ! I hope this helps

SOURCE: running lean

Have you a leak in the exhaust??even a small leak will cause the lambda value to be out check your exhaust

Testimonial: "will do thank you!"

SOURCE: ford f150 2003 po171 always

Code Po171 indicates a lean condition on cylinder bank #1 of the engine. This is the drivers side of the engine. I would suggest replacing both front oxygen sensors as a pair to start. An oxygen sensor has a life span of about 5 years and yours are now 9 years old if they are original. When they get older they are slow to respond to changes in the oxygen content of the exhaust and can trigger a code Po171. If you continue to have the same code set after the replacement of both oxygen sensors then it is time to find out why your engine is running lean. Some of the most common causes are an ignition misfire and a vacuum leak. I have also seen Fords EGR flow sensor (known by Ford as Delta Pressure Feedback sensor) to cause problems like that as well. A good mechanic with a scan tool can usually spot a problem like that in a few minutes.