I recently failed my emissions with a P0171 code. I know this could be a lot of things, but there are some other symptoms that go along with the problem.

My engine has a faint knocking that sounds like a misfire. I tried higher octane gas and the sound kept on.

I idle rough down at 500-600 rpm's, and have stalled in the past. I changed the fuel filter and that helped with the stalling, but there is still some occasional hesitation. Once I get going it runs great, but my fuel mileage is down to 15-16 MPG highway.

I cleaned the MAF and throttle body tonight, but I am sure there is more to all this. I am going to get a new hose for my PCV valve because it seems to fit over the valve pretty loose.

What else do I need to do?

Also, I disconnected the neg. terminal to take off the MAF and of course the CEL went off and the code is cleared. How long or far do I have to drive before I know whether or not the problem is fixed?

I know I'm throwin' a bunch at y'all, and I appreciate any feedback.

Thanks.

 

you should reall learn to use the search feature on this forum.

p0171 is a lean on bank one, most often caused by a vacuum leak somewhere. Go check all your hoses for crack/dry rot or leaks/holes.

 

X2

 

Get a can of carb cleaner and while the truck is running spray some on the vacumme lines, one at a time. If the idle picks up then right where you sprayed is your leak.

 

Personally... I wouldn't go around spraying carb cleaner all over a hot motor... I'd go more for the soapy water and look for bubbles.

 

Well no, you dont do it hot. I figured everyone would have figured that out. Best time to do it is first thing in the am after the high idle has calmed down.

 

I had to say it lol Can't ever tell with people on here haha.

 

I know this thread is many years old, just thought I'd add a note for newbies that soapy water does not make bubbles when there is vacuum in a line. That's negative pressure and if there are bubbles the bubbles are getting sucked into the line. Soapy water is for positive pressure, like leaks in compressed air systems or natural gas & propane piping.

Unless I'm full of crap here. If that note's wrong, someone tell me how!

 

no you're good. In order to use the soapy water method, you have to disconnect the vacuumsystem and pressurise it from an outside source.( i.e. air compressor. )