Hell all, I have reading the forum for a while and decided to join in, I recently bought an 03 f150 fx4, 5.4 engine with 242k miles and drives awesome, it has been well taken care of. My service engine light came on and started to hesitate at idle but it it drives fine when you take off. I had the code pulled and it was the famous PO0171 only this code showed up, have been reading about the pvc elbow behind the intake manifold that could cause this. When i was looking around today for the elbow I stumbled upon this, can anyone tell me where this 2 hoses go? They look to be disconnected for unkown reasons, I've been looking around can't figure out where they go, could this be my problem?[IMG][/IMG][IMG][/IMG]

 

Yea that's for your cold climate system. Coolant loops thru and around the PCV system to thaw when moisture freezes up the PCV system. It's bypassed because someone has installed the wrong valve for your application. You can get the correct replacement at the dealership. It's not hurting anything running it the way is unless your live within below freezing temps.

That alone isn't the reason for your DTC PO171. But yes, a leak within the system could definitely cause that code. Check the entire PCV system, it's most likely a small leak between the firewall and back of the motor.

Also, you can disconnect the battery, clean the MAF sensor and check for any possible leaks after the MAF with the air intake.

If all PCV, Vac lines and grommets have been thoroughly checked, you most likely have a bad intake gasket.

 

lol, I bet someone couldnt figure out how to disconnect it so they just bought the wrong one and plugged it in, re routed a new hose. Then where is the original hose going? Not hooked up I would imagine