error code po171 & po440?

[cs10471]

I have a 98 Tahoe with 5.7 and has had check engine light since I got it a few months ago.Fuel pump went out on me and had it and fuel filter replaced. I get po171 and po440 every couple of days.it runs fine and I'd like to fix this.the Tahoe is my long term project so any help I can get to point me in the right direction would be a great help. Thanks

 

[Ice98]

A little googling turns up:

http://www.obd-codes.com/p0171

http://www.obd-codes.com/p0440



These 2 are listed as not having much effect on drivability, with several causes, follow the links for more info

 

[cs10471]

Thanks for the reply.I have been googling it and was wondering what anybody ran across to fix the codes from their experience. I'll start with the gas cap and see what happens.thank you again

 

[lesterl]

P0171, system too lean Bank 1 (drivers side)
P0440, evap emissions system leak/ malfunction

As far as the first one, it can be caused from plugged injectors to an exhaust leak to a bad oxygen sensor.

Second one could be Fuel cap bad (vent is stuck open so the vacume wont build in the tank), bad evap sensor, purge valve, crack in the tank/ lines, etc...

 

[cs10471]

Thanks a lot man.that gives me a good head start on things to try.I'll try your suggestions and see what happens.thank you

 

[lesterl]

Not a problem, only having a lean code on drivers side kinda narrows down possibilities, but an exhaust leak can cause extra 02 to trigger the sensor in the exhaust to being too lean..... Of course it could be actually too lean (lack of fuel to one or more cylinders i.e. bad injector - I would seafoam the tank and the intake). If it had been both banks lean we could suspect fuel pump/ filter as well as an intake leak and several other issues, but since it only threw the 171, then that kinda narrows it down.

 

[cs10471]

Thanks for the great response.I thought about seafoam but am scared it flushes something loose and makes it worse or damages something.have you had good results using it?

 

[lesterl]

I have NEVER ran seafoam in the oil, that being said, I have ran it thru a vac line and in the gas tank.

Vac line is a top end cleaning procedure, tank is for injectors and cylinders.....

 

[cs10471]

I see.I'll pick up a can and give it a shot this weekend.thanks for the advice