P0171, P0174 Banks 1,2 lean

[limited cv8r]

Hi, I have had a friend come to me with a 285kw VY clubby which has been running fine until the other day. His check engine light came on,after checking for codes I retrieved P0171 bank1 lean, P0174 bank2 lean, plus all his ltft's were at 23.5% for both banks. I cleared the codes for him and reset his trims so we could check it again a bit later. He informed me that by the next day the check engine light was on again. As a quick fix until we had time to investigate I just reflashed another standard 285 HSV tune into it to see if the problem went away. No such luck, has anybody got any ideas what or where to look for this problem or has anybody else experianced this type of behaviour before?

[TAQuickness]

That could be quite a few things.

Check the air filter
Check the fuel pressure
Install new fuel filter
Check for exhuast leaks (top end cleaner, i.e. seafoam, makes leaks easy to spot)
Check for intake manifold leaks (carb cleaner or starter fluid makes this easy)
You can try new O2's but it's not likely both would go out at the same time.

I'm sure some others will chime in...

[ViolatorTA]

Almost every time I see these 2 codes at work I find a broken or disconnected vacuum line. Now and then it'll be intake gaskets/TB gaskets.

When that fails I check for low fuel pressure.

[limited cv8r]

Thanks for the replies and hopefully the answer to my problem.As stated before by other members, The EFILive community is always great for help from other members.

[limited cv8r]

Got a chance to have a look at my mates car today. Found the clamp for the rubber adapter that joins the MAF to the intake pipe had come loose and the adapter had started to slip off the intake pipe allowing the engine to suck air in after the MAF. Thanks again for the help fellas & I guess look at the basics first.