Check engine code P0171

[Wasatch Rebel]

My check engine light keeps coming on. I've cleaned the MAF and the light has gone away for a week or two, but then has come back on. After the last time I cleaned the MAF, the light only went off for about a day, then came back on. My code which I got checked at Autozone says it could be 1) low fuel pressure, 2) Faulty MAF/VAF sensor, 3) Cylinder misfire condition, 4) Faulty H02S/AF sensor, or 5) Large vacuum leak.

I'm not noticing any rough running, except for once or twice when I first pulled it out of the driveway in the morning. My guess is it isn't the fuel pump or I'd be having more trouble, and I should be able to hear a cylinder misfiring condition, or a large vacuum leak, so it's probably one of the sensors. Any idea which one, or if my guesses about the other possible causes are right?

 

[Mauzer]

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

 

[Wasatch Rebel]

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

Thanks, Mauzer. That is helpful in providing a checklist to go by. Some of the stuff is a bit beyond my expertise, but I'll see what I can find out.

 

[004Gunner]

P0171 is usually the A/F ratio sensor. I love the FSMs but I never found the trouble shooting steps to be listed in any logical order. If you have more than 100k miles then the sensor is probably bad

 

[Wasatch Rebel]

P0171 is usually the A/F ratio sensor. I love the FSMs but I never found the trouble shooting steps to be listed in any logical order. If you have more than 100k miles then the sensor is probably bad

Thanks, 004Gunner. I have 130k on it, so I'll check that out first.

 

[1800AskMatt]

P0171 is usually the A/F ratio sensor. I love the FSMs but I never found the trouble shooting steps to be listed in any logical order. If you have more than 100k miles then the sensor is probably bad

I thought P1135 was A/F sensor?

 

[tyr0981]

My P0171 was a major PIMA to figure out!

i'll spare you the months / years of odd things that would trigger it. Basically, the vacuum line that comes from the Intake Silencer box, wasn't getting enough vacuum , this line directly controls the amount of fuel being sent to the engine. When i did the ISR mod i connected that vacuum line to a port that didn't provide enough vacuum at all, and it was constantly throwing a p0171, every time she started & or ran somewhere.

I then i moved that vacuum line back to the intake pipe i put on in place of the intake silencer, drilled a holed and expoxy'd a vacuum fitting to the pipe, and bingo not another code since. my only complaint now is i went from almost 18MPG, down to 16MPG this afternoon it says 15.9 :mmph:

My engine sounds allot happier, and has a noticeable increase in power too. Rarely is it the A/F meter failing, it has happened, but usually it's an o2 sensor or if someone has been messing with there engine components.....

:rockthrow:

 

[1800AskMatt]

Man, I was just going over everything I have done in the last month, and was wondering about that hose.

Thanks for the input!

New mod correction in progress

I LOVE THIS SITE AND ALL THE MEMBER HELP!

Thanks again... will keep you posted.

 

[flatboy]

I too am getting this code after I did my rear mount turbo, I wonder what I did with that hose?

 

[kingin]

Get a can of brake cleaner and spray around intake plenum and throttle body when car is at idle and see if any surge in idle. Had similar issue thought was maf cleaned that then replaced a/f sensor still had cell. Ended up having a leak at the intake manifold/plenum.