tjsilva

Could the cause of my P0171 code be a leaking vacuum pump? 2006 a4 2.0t. any idea where i should start. I did a tune up this weekend replaced fuel filter, air filter, plugs, and coil packs need to chase down pesky code. I didn't think those would fix the problem but figured it was time . Any help would be greatly appreciated code comes and goes.

zee7

Hi,

P0171 - System too lean in bank 1
Meaning there is more air supply than fuel to the engine.This will fluctuate gas mileage. There will be hesitation in engine/acceleration.

1) Replace Upstream Oxygen sensor (Lambda sensor/Air-fuel ratio sensor) if no changes then check for vaccum leaks usually leaks from worn out hoses or loose gas cap

if that doesn't fix then its going to be hectic job next

2) Bad high pressure fuel pump

3) Intake manifold cleaning & gasket replacement

3) Bad fuel injectors (if black smoke coming out from tails)


Hope it helps!

Chachboi

With a scan tool clear your codes then drive about 50 to 100 miles as gently as you can. If the check engine light stays off then drive it hard (in sport mode) and get the pedal to the floor a couple times, if it kicks on from that you're most likely being starved of fuel. it will most likely be your low pressure fuel pump (inside the tank). Hpfp and vacuum leaks tend to be most present at idle. I chased this code by replacing the vacuum pump, diverter valve, various vacuum lines, fuel filter, and hpfp before this.

yuvalw123

look at the purge valve , its easy and cheap repair.