p0171 won't go away

[ocreptileguy]

This code will be the end of me. I have a new MAF sensor, new upstream a/f sensor, new vacuum lines. Code has been on for 3 weeks now and won't go away. When I put in the new A/F sensor it went away for about 60 miles then came on again.
Vehicle has new valve cover gaskets, spark plugs, PCV valve w/ new grommet, fresh oil all done a month and a half to 2 months ago.

Currently I put new vacuum lines on tonite, started the car and cleared the code then drove about 15 miles and it came back on.
Got home, cleared the code again, then cleared the pending code, then cleared the pending code a 2nd time and the car shut off on its own.
I started it right back up and the CEL didn't come on. I shut it off and just disconnected the battery to reset the ECM in hopes this may help.

I'm lost from here. The car has stalled on me 2 times both when coming to a stop at a light and it was days apart.
I have a regular paper air filter in.
Someone help please!

 

[ocreptileguy]

Rig specs
99 3.4L 4 auto limited 180100 miles and I'm pulling the code from my scan gauge 2
Fuel filter changed approx 7 months ago and fuel efficiency since the code has come on has gone down. Getting about 210-220 miles per tank ( approx 14-14.3 gallons per fill up)

 

[Troybylt]

99, Is your charcol canister by your spare tire or under your hood? Eitherway check the vaccum lines to and from your charcol canister.

I had a small inch and a half long 1/4 thick elbow line that went from a plastic tube on the charcol canister the size of a wd-40 straw to a small sensor under the hood Mointed to the firewall. This had come loose, was still 'in place' but not secured to the sensor nipple and it was throwing a code for that.

You may want to start useing a meter to test and see if you have any breaks in your wiring harness.

Are you running a K&N style air filter?

 

[ocreptileguy]

Thanks, I'll check that. No I'm not running a K&N

 

[19963.4lsr5]

It could be as simple as a exhaust leak Pryor to the O2 sensor.

Could also be low fuel pressure. Have you checked it? The gauge is only 20 dollars at harbor freight.

 

[ILRunner98]

I would check fuel trims if you have a way to get that data. Im guessing an injector or two are running lean. Could also be the evap system purge valve. I have seen those cause a lean code too.

 

[ocreptileguy]

I plan on checking fuel pressure tomorrow. I just ran a simple smoke test and saw some smoke that looked to be coming from the lower plenum. Which would make sense since I reused that gasket 2x after taking the plenum off. Fingers crossed that's all it is

 

[angus]

I would say if fuel pressure checks out definitely also check fuel trims. Could very well be a bad injector or two, it's a pain but you could try swapping injectors from bank one to banks 2 and see if the code follows.

 

[ocreptileguy]

I replaced plenum gaskets and so far it seems like that was the issue. Idle is better. Drove 20 miles and shut the car off 3 times and no cel