P0171 - System too lean: what can cause this?

[lsintoronto]

P0171 - System too lean

It's a 2004 LS8 Sport with about 75K miles. The Check Engine light came on last night and is throwing the code "P0171 - System too lean".

What can cause this and what could happen? I cleared the code so will watch and see if it comes back.

I did change all the plugs about 2 months ago using OEM plugs and also changed a bad COP (#3 I think) back in August.

Thanks!

 

[Lincoln Jealous]

could be either vacuum leak, bad EGR differential pressure sensor, dirty MAF sensor something like that

 

[tireman]

vacuum leak

Yes thats a vacuum leak after the MAF. check for split hoses. loose fittings, they start to fail around 75k.

 

[Stack]

VACUUM LEAK!!!!!

Lean conditions are always a vacuum!

Ask me how I know

 

[PetesSweets86]

too lean? fatten that baby up!

 

[blairrf]

Check your plenum

I had the same codes...replaced the EGR stuff (most of the parts in the engine compartment) and tried a few other things.
I needed to get it inspected and cleaning out the plenum finally solved the problem - there was a lot of gummed up stuff in there. Haven't had DTC 171 since.

 

[tireman]

Maybe

Most likely it is a vacuum leak, however, I read that it could be that the MAF sensor is carboned up and needs to be cleaned. Check the wires to see if they are nice and shiny. This may also be associated with starting problems.

 

[lsintoronto]

I had the same codes...replaced the EGR stuff (most of the parts in the engine compartment) and tried a few other things.
I needed to get it inspected and cleaning out the plenum finally solved the problem - there was a lot of gummed up stuff in there. Haven't had DTC 171 since.

Plenum? Is that the part/tube that the MAF wires are plugged/screwed into, and is part of the air filter box? I took the top of the airbox off and sprayed electrical contact cleaner on the sensor area and reinstalled it.

The code has not come back since I cleared it prior to using the contact cleaner so whatever cause the code has not re-occurred yet.

I did find that the top of my airbox is cracked near the inlet area close to the sensor but I don't think this would cause a code.

 

[joegr]

...
I did find that the top of my airbox is cracked near the inlet area close to the sensor but I don't think this would cause a code.

It can if it changes the airflow pattern enough. In any event, an unfiltered air leak is not something that you want. At least put some duct tape over it.

 

[Lincoln Jealous]

too lean? fatten that baby up!

cheezy poofs

 

[BigBoiLS]

i just had the same code. im pretty sure i had the pcv (i think that was the part) leak and i fixed that. but i had the code come up again. the weird thing is if i have my car in park while idling the car will shut off has anyone heard of anything like that happening, because of a vacuum leak.