low vacuum / PCV problem ?

**zebra78** · 11-08-2009

Hello everyone. I just bought a '99 GTP, all stock, and I am getting P0171 lean bank 1 consistently...

Got set up with a scan tool on my laptop and sure enough, the LTFT's sit at 16.4 at idle and slow cruise, they seem to lower when the engine is under more load.

Except for 10 in/Hg at idle, all other sensors look good and I have started to examine the engine for vacuum leaks.

I noticed that if I remove the oil filler cap while the engine is running I get a stumble out of the motor, and when I spray carb cleaner in the front valve cover, the motor does change rpm temporarily.

Is this typical, or am I in the right area? Should I check the PCV system? The PCV valve itself is new.

Thanks for any advice,

Jason

**duane9586** · 11-08-2009

sounds like a vac leak I had the same problem with my ltft's being at 16.4. First it was my s/c gasket fixed that and still had a leak. Ended up being my oil dipstick was broke right were the o-ring is on the inside. Now they sit around 8 at idle but i also added rockers and a ic so i have to tune it now. It is normal for the idle to change when you take off the oil cap. Keep trying the carb cleaner and see if anywhere else is leaking. Also I was told if you scan your IAC and they are under 50 you have a leak.