Check Engine Light And Code P0171, what to look for with a code P0171
 

here is my issue. I got a 2001 Sonta with 4 cyl engine. The check engine light came on after I washed the engine. I did not use high pressure. I just used a scrub brush with soap and cleaned everything real good. then lightly hosed off.
I have changed the fuel filter, checked for vacuum leaks. I took a cap and closed off intake and pressurized it to see if I can find a air leak.. I can not hear so good so finding a vacuum leak with motor running was pointless. I also sprayed a sensor safe cleaner to clean the sensor in the intake.. And I used that same cleaner to spay around every vacuum line I could find, no noticeable engine change..
It cranks and runs OK. Has a little hesitation from time to time and bucks every now and again. Nothing major. But I know something is wrong...

I am stuck, i hate taking any car into shop. And i like working on my own stuff and getting it fixed, but this is kicking me hard......

I have cleared the codes 3 times and they come back.. I have not disconnected the battery yet....

P0171 means the engine is running lean. That usually means the MAF sensor is dirty, faulty or there is a vacuum leak after the MAF. When did you clean the MAF, before or after you got the code? It may still be dirty, faulty or the connector may be dirty or bad.

I have cleaned the MAF many times and it makes no difference...

Then I'd have the MAF checked out. It may be faulty. Also look for a vacuum leak between the MAF and the intake manifold.

How do I test the MAF..???

I cleared the code and it still returns.. I have pressurized the intake system and no leaks.. I am at a lose on this..

Any one know how to test the MAF?

Any one? this sucks... And I would hate to have to bring it to a shop for something simple///

Well I know its not the O2 sensors. I unplugged one at time then reset codes. then drove car till Check engine light came back on. Instead of the p0171 it had 2 others. One for O2 heater and the other for O2 sensor missing.

I then unplugged the MAF sensor and reset codes. After driving i get P0171 again and 2 more codes related to the MAF so I would assume the maf is good too.

My only idea maybe the vacuum switches on the back side of the motor. I tried pressurizing them and they dont leak. But maybe when vacuum on them they are pulling outside air. I have sprayed all kinds of stuff on them with engine running and no change. I am at a total lose on this.

Well it was the MAF sensor. replaced it and all it good.........