I just bought a 2000 for e250. I am reading two codes. P0171 & p0174 codes. I have cleaned the maf sensor and also installed a new pc valve. The problem is still there. It might be a vacuum leak. I am not sure how to check for this without a fancy machine. Please help and what else could it possibly be. Thanks

 

Need to watch data-stream on a good scanner and see if O2's are lazy.

 

The information on the following pages might be helpful to you: https://sites.google.com/site/fordf1...P0171P0174-Fix

 

I believe the E250 in 2000 was still using the metal intake manifold. Underneath the throttle body is a rubber elbow that is part of the pcv system. This elbow over time will usually develop a hole in it allowing un-metered air to enter the engine. This would be the first thing to check. The rest of that line runs towards the passenger rear side of the intake to another elbow. I'd check this one next since you can take the doghouse off inside the cab and get to it very easy from there. Keep us posted.