P0171- help
P0171- help
My car has a code p 0171. My car idle like crap when cold and better when it's warmed up. When I turn on the a/c the idle drops to about 500 and with it off it's around 900 rpm. I cleaned my throttle body and my idle air control valve in hopes it will fix my idl, but it's still the same. Don't know what else to do. I Checked for vacuum leaks. None at all.
P0171 is a lean bank one condition. But the car drives fine. It just idle weird. Usually when you turn on the a/c the rpm should go up and the iacv is suppose to compensate for the load. I'm not getting a check engine light for any of that. Just the lean bank 1
Driver School Candidate
Joined: Sep 2012
Posts: 6
Likes: 0
From: CA
P0171 Check Engine Light
There is an air leak somewhere, sucking in more air in the combustion system than optimum.
Could be as simple as a loose, untightened gas cap. Women do this a lot. Try to tighten the gas cap until it makes screeching noise. Repeat 2 more times to make sure it's sealed tight.
That usually solved the PO171 system too lean problem. Drive 2 trips and system should turn the PO0171 CEL off.
If CEL is not turne doff after a few trips, reset the CEL code with an engine scanner (can be bought in eBay for $10). Drive around a few more trips. If CEL comes back and scanner still shows code P0171 then there may be other air leaks in the vacuum hoses around the air intake box.
Spray water on the vacuum hoses then run the engine, listening, looking for sucking noise where water is sucked in. Fix the leaks with tape or epoxy glues or new hoses.
Could be as simple as a loose, untightened gas cap. Women do this a lot. Try to tighten the gas cap until it makes screeching noise. Repeat 2 more times to make sure it's sealed tight.
That usually solved the PO171 system too lean problem. Drive 2 trips and system should turn the PO0171 CEL off.
If CEL is not turne doff after a few trips, reset the CEL code with an engine scanner (can be bought in eBay for $10). Drive around a few more trips. If CEL comes back and scanner still shows code P0171 then there may be other air leaks in the vacuum hoses around the air intake box.
Spray water on the vacuum hoses then run the engine, listening, looking for sucking noise where water is sucked in. Fix the leaks with tape or epoxy glues or new hoses.
My car has a code p 0171. My car idle like crap when cold and better when it's warmed up. When I turn on the a/c the idle drops to about 500 and with it off it's around 900 rpm. I cleaned my throttle body and my idle air control valve in hopes it will fix my idl, but it's still the same. Don't know what else to do. I Checked for vacuum leaks. None at all.
Driver School Candidate
Joined: Sep 2012
Posts: 6
Likes: 0
From: CA
P0171
Could be the Mass Airflow Sensor is dirty or broken. It's flat rectangular mat ch box size box sitting on top of the air input duct right behind the air intake filter. It's held down by 2 phillips screws. Unplug the connector, remove 2 screws, take it out and spray carburetor cleaner on the long pendulum look alike sensor and all electrical contacts just to be sure.
If that doesn't work, the MAF may be dead, or there may be air leaks or unplugged vacuum hoses. Check and make sure all rubber hoses around the air intake box are plugged in and secured.
If that doesnt solve the problem, idle the engine, crank up the throttle and listen for hissing sound of air being sucked into leaks on vacuum lines.
Vacuum leaks can also be found by blowing lots of cigarette smoke into on of the larger vacuum hose, and look for smoke leaks.
Good luck and tell us how it goes.
If that doesn't work, the MAF may be dead, or there may be air leaks or unplugged vacuum hoses. Check and make sure all rubber hoses around the air intake box are plugged in and secured.
If that doesnt solve the problem, idle the engine, crank up the throttle and listen for hissing sound of air being sucked into leaks on vacuum lines.
Vacuum leaks can also be found by blowing lots of cigarette smoke into on of the larger vacuum hose, and look for smoke leaks.
Good luck and tell us how it goes.
My car has a code p 0171. My car idle like crap when cold and better when it's warmed up. When I turn on the a/c the idle drops to about 500 and with it off it's around 900 rpm. I cleaned my throttle body and my idle air control valve in hopes it will fix my idl, but it's still the same. Don't know what else to do. I Checked for vacuum leaks. None at all.
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Driver School Candidate
Joined: Sep 2012
Posts: 6
Likes: 0
From: CA
Most Toyota or Lexus cars would use a standard Mass Airflow Sensor, which is a rectangular black plastic box, the size of a match box, on top of the input air filter box. It's held down by 2 philips screws.
Remove the box, you will see the sensor, a small black pendulum, looks like a cotton swab, hanging down into the air stream. Over time dirt can bind up the pendulum, making it look like less air comes into the cylinders, therefore the ECU commands the fuel injectors to inject less fuel, hence the P0171, system runs too lean.
I sprayed carb/choke cleaner into pendulum's joint to free it. The CEL went away and has stayed off for 3 weeks and how many countless trips.
Good luck .
Remove the box, you will see the sensor, a small black pendulum, looks like a cotton swab, hanging down into the air stream. Over time dirt can bind up the pendulum, making it look like less air comes into the cylinders, therefore the ECU commands the fuel injectors to inject less fuel, hence the P0171, system runs too lean.
I sprayed carb/choke cleaner into pendulum's joint to free it. The CEL went away and has stayed off for 3 weeks and how many countless trips.
Good luck .
Last edited by PETERPAN20; Sep 23, 2012 at 11:23 PM.
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