P0171 DTC - sys too lean (Bank 1)
 

1999 Chevy 5.3L Auto with 150,000 or so miles. I've noticed it missing a little for a while and just figured it was time to do plugs and wires, so I wasn't too worried about. The check engine light is starting to come on and it will go off after a while. I finally got my hands on a scan tool when the light was on and it showed the P0171 code.

I know that this can mean a vacuum leak, MAF dirty or bad, fuel filter dirty, etc. My question is...what do you all think I should address first in trying to figure it out. Is there one thing that outweighs the rest when it comes to this?

Any information would be appreciated. Thanks in advance.

Cory

Re: P0171 DTC - sys too lean (Bank 1)
 

No one has any information/advice?

Re: P0171 DTC - sys too lean (Bank 1)
 

chances are its the very common intake gasket issue or cracked intake. dorman makes a replacement intake the fixes the issue. did it start out as a slight quiver now and then in the idle and get worse from there?? if so chances are you need an intake and gaskets. Your well overdue for replacing the intake at that mileage they rarely ever go that long.

Re: P0171 DTC - sys too lean (Bank 1)
 

have you ever ran E85? it attacks the "rubber" on the intake gaskets.
what are your long term and short term fuel trims at both idle and 2000 RPM for both banks? I suspect that bank 2 is getting close to setting a P0174. I would also look at the missfire data stream

Re: P0171 DTC - sys too lean (Bank 1)
 

It started out as a miss...just like a faulty spark plug or wire would do. That's why I thought it just needed a tune up. It basically did it in overdrive pulling a hill or something of the sort. I would say it's a little more constant now in overdrive, but that's about the only time I see it. Sometimes when idling it runs just a little rough. Does this sound like intake issues?

Do you happen to know the dorman part number for that kit and how much they usually run? How big of a job is it to replace that?

Thank you for your help.

Re: P0171 DTC - sys too lean (Bank 1)
 

I'm going to show my ignorance here...what is E85? I haven't had the fuel trims checked. I don't have a way of doing that myself. I'm just a simple guy that can do mechanicing with normal tools. That's why I'm prodding you all for information.

Thank you for your help.

Re: P0171 DTC - sys too lean (Bank 1)
 

these symptoms sure sound alot like the old Vortec 5.7s with sticky valve guides.

Re: P0171 DTC - sys too lean (Bank 1)
 

heres a link. most decent auto parts stores should have them in stock.https://www.dormanproducts.com/cgi-b...tegory_list=:0 part number is 615-183 comes with gaskets etc. E85 is 85% ethanol. most regular fuel now has at least 10% ethanol as a gimmick to reduce emissions which did nothing but run up the price of corn.

Re: P0171 DTC - sys too lean (Bank 1)
 

bad intake gasket, bad o2 sensors dirty maf, vacuum leak so many things it can be