So i just(about a month ago) replaced both forward O2 sensors(had a light). I just got another light, this time the code is mixture to lean. What are some causes of this(could it be anything with the cat, or my computer). Saturday My wife and I were in town and I was waiting for her in a parking lot, and the engine started to idle really low and started to sound like I had a big cam in the engine. Could anybody help me out with this? Thanks Scotty

 

vacuum leak? check the pcv elbo right on the throttle body.

 

the pcv elbo should be on the back of your intake. if its sucked shut or rotted with a hole(s) then its no good.

 

Matts right , but you should post the codes to be sure. If you had Codes PO171,174, Yea head for that elbow. Your new O2's are reporting properly.

Elbow is here -




Scotty - That's my 98 5.4L. You need to post your engine size for accurate info.

 

Sorry yeah its the 5.4. I will check that elbow tomorrow. Thanks for the quick responses and all the help lets see if this is the problem. Can I just pick up a new elbow or is it a elbow and hose combo? Thanks Scotty

 

you can pick up just the elbow.

 

Yea, you can -



But most want you to purchase the whole PCV assembly . I would get the whole thing on an older truck. Just because that plastic length of line between the elbows gets brittle over time and has been known to crack.

Complete system -

 

Read post #6 here - (click on link below)

https://www.f150online.com/forums/en...ning-lean.html