P0171 is driving me crazy!

[jimjam41]

Hi, gang! I'm new here but I've been lurking for a bit. Here's the rundown on the problems I'm having.

I have a 2015 Sonic LT 1.8L a little over 161,500 miles.

So, about a month ago, my Sonic started having a rough idle and the engine would shut off when stopped at a red light. My codes were P0420 and P0171.

Took it to a shop and they say "you need a new Cat and flex pipe" and me being a layman, said "cool, do what you gotta do." So I have a new cat and flex pipe. P0420 is gone. After about a days worth of driving, she starts idling rough again, engine shuts off when stopped at a red light. P0171 code is back. So, I put on new upstream and downstream O2 sensors. Code went away again for a day, then the same troubles came back.

Had my dad check the the valve cover, which was leaking oil into my ignition coil. So today, we soaked up the oil, then replaced the old ignition coil, spark plugs and the valve cover with a new one (new gasket, too.)

Drove AMAZING for about 2 hours today, until I get the same old codes and a new one. P0420, P0171 and now P0131. Now, it's having a hard time starting up and it's shutting off again whenever I'm not moving.

Also, We've checked the MAF, cleaned the sensor. Really hoping it's not the fuel pump.

So, yep. Can anybody throw me a bone on what could be my problem?

Also, sorry if I'm posting in the wrong place (forgive me, Mods)

 

[JTee2017]

The original codes you got seem to indicate a lean condition, which would result in the ECM trying to compensate by injecting more fuel. Given the high mileage on your car, and a lean condition, it may have been enough to take out the catalytic converter. Has the engine also been using any oil normally?

I would check all the vacuum lines including the one to the vacuum brake booster going from the rear side of the intake manifold to the brake booster. I had a cracked hose connector at the manifold side and it caused the symptoms you describe. But. .. just about any vacuum leak might do the same.

There are ways to isolate a vacuum leak like using a small butane or propane source around vacuum lines. .. kind of dangerous. But when the butane or propane gets sucked into the leak , ... the engine will smooth out. Search Youtubes for how to find engine vacuum leaks.