BDR1973

My HHR LT 2.2L had a P0171 off and on for a year. Mine ended up being a faulty O2 sensor (upstream) that was the issue.

Tinky

Did you have a hard time starting the engine?

donbrew

The fact that the O2 sensors have their own set of DTC codes makes it very rare that the P0171 is a bad sensor. However, if there is air getting through it or the bung that could cause the code.

P0171 means that unmetered (by the MAF) air is entering the system somewhere between the MAF and the #1 O2 sensor. Or, there is a shortage of fuel.
Or, exhaust gas that should be getting to the #1 O2 sensor is going somewhere else (cracked flex pipe, bad exhaust gasket).

The #1 O2 sensor controls the A/F mixture. The #2 O2 sensor monitors the health of the catalytic converter.

BDR1973

Tinky, i did not have a hard time starting the engine. My fuel trim was not reading correct. But is now, four weeks and no CEL light on (knock on wood).

Tinky

Thats a good information to know !

I have questions that may be easier for you guys to answer:

1. The only problem now is to start the car... it may take 4 or 5 tries. OnCE it starts, it runs fine. No hesitation, no rough idle, no pulling. If it was a bad fuel pump, shouldnt i have problems also while driving???

Where would you start checking for the problem ???

whopper

Rather than going all the way back to square one with asking the same questions as in the first couple posts, why not start checking some of the suggestions already given, and follow-up on checking the fuel pressure?

donbrew

If the integral check valve was not working that would cause all of the priming fuel to return to the tank. So, no not necessarily.

So, the p0171 is now magically gone?

I do not know how disconnecting the MAF would cause the engine to run better and not cause at least 1 DTC code.
If removing the MAF made it run better you should just leave it disconnected, because something is catastrophically wrong.

Every time I have forgotten to reconnect it the engine ran like crap and the CEL came on with 4-5 DTC codes.

I feel like I'm being played, or you are forgetting to mention a lot of things.

Tinky

Ok these are the updates:
The fuel pressure test was ok !
With the code P0171 lean bank one, i started the car after a few tries. At this point i unplugged the MAF and kept on running. I turned the engine OFF and tried to start with the MAF unplugged. It did start and run at the first try ! .. showed several codes about MAF , temperature, a total of 6 codes all related to the MAF . Tried to start several times and worked first try. ALSO, the P0171 WAS NOT there any longer ...
I took my OBDII and erased the codes .... the engine shut off by itself.
Last i plugged the MAF on again, and we are to the same point.... hard to start.

Do this make any sense to you guys ???

Tinky

The MAF sensor was replaced about one week ago.
And i am assuming the connector and wires to the MAF are ok since once i unplugged it the computer read it right away.

Tinky

Btw, i have a problem and id never play about it. I need help since i am not a mechanic. I will try to post a video or make one for youtube and post the link if that would help. The plug/unplug of the MAF idea i got it from here:
On youtube look for:
" How to tell if you need a Mass Air Flow sensor. Auto repair. Wesley Harrison "