Hey everyone,

My truck (2001 F150 4.2) has been running lean (both banks) for a while now. However, after many rounds of troubleshooting, I've been unable to determine the cause.

The only symptoms are a slight decrease in mpg and an rpm loop effect during cold weather start up.

I've...

-cleaned MAF (two wires are still intact)
-cleaned IAC
-cleaned TB
-Removed Intake manifold to check for gasket leaks
-Replaced PCV valve and grommet around it.
-unable to find any leaks on the vacuum lines. (I might be missing 1 or 2, a diagram would be nice!)
-replaced fuel filter

I'm looking to sell this truck soon, and didn't really want to sink a whole lot of money into it, but would like to have this resolved.

After searching through numerous posts, I see many people have problems with the PCV elbow. Where is it on a 4.2. I know it's near the firewall on other engines, but after removing the intake manifold I couldn't find it.

Any suggestions or other ideas?

Thanks!

 

The elbow is located under the thothol body(SP). Also you mite want to look at the hose that is right past the pcv. It connects to the lower intake. The elbow is $15 at the dealer. The hose you can just use 3/8 bulk hose around a $1 at autozone. Goodluck Ben

 

So the PCV is under the throttle body on the 4.2L. It has 2 lines coming off of it and the vent hose that leads to the rear pass. side valve cover where it seats into a rubber grommet. Mine seems to be loose there and doesn't seat very well. I too have been dealing with this air leak problem and the 171 and 174 codes. If you get the P2195 and 2197 could that really be the o2 sensors going bad. Says they are "stuck lean"

 

Well I fixed my PCV issues!

I sold the '01 F150 and bought a '08 F250.