I realize there are several existing threads regarding P0171/P0174, but when browsing them I didn't see anything that helped with my particular situation, so I'm hoping somebody might be able to give me some insight. Sunday, I climbed under the hood to change my spark plugs, and after removing the air intake and pulling the PCV tube out of the way, and disconnecting the power steering fluid reservoir and pulling it aside, I pulled the coil off of my #6 cylinder (I'd recently replaced the plug on #5 cylinder while changing out the coil, so I wasn't gonna do it this time) and went to put my 5/8 deep socket onto my extension, only to discover that somehow my extension was damaged to the point that I couldn't get the socket on it. Since I couldn't do the work, I decided I would run by the store in a day or two and grab a new extension, and I put everything back together. I started the truck back up to make sure #6 coil was seated well and that it wasn't gonna cause a misfire, and the engine started right up and ran strong. Yesterday, on my way into work, I got a steady burning CEL. when I got to work and parked the truck, I plugged in my code reader half expecting a P0306, but was surprised with a P0171 instead. I cleared the code, and this morning I got the CEL again, so I read it when I got to work assuming it would be P0171, but it was P0171 AND P0174. What in the world could I have jacked up that would cause first one, and then both? The truck is still running strong, and has no issues starting up.

 

Vacuum leak, check PCV elbow on back of intake.

 

That's the best I've come up with so far, too. Since I messed with it, I figure I may have accidentally bent it too far and cracked/torn it, so that's the first thing I'm gonna check after work today.

 

I would have to agree with the vacuum leak. also check your pcv and make sure it works like it is suppose to.

 

Well, I feel like an idiot. I checked the PCV elbows and they were fine, then while I was standing there with the hood up scratching my head and wondering what on earth I could have messed with that would cause a vacuum leak, I noticed that the boot around the wires to my MAF sensor was popped part way out...which of course must have happened when I pulled the air intake over to the side to gain access to the spark plugs. Popped it back in and drove the truck a bit then plugged in my code reader, and no codes were present. Drove into work this morning and plugged it in again...still no codes. So there you go.

 

lol well glad you got it figured out bud.