I have codes P0455 EVAP Emission Control System Leak (large) plus P0171 system too lean (bank 1) and P0174 system too lean (bank 2). The truck idled like crap and even stalled out when you came to a stop. While driving you could tell it was at a higher RPM than i was asking for and if you shifted into netural while moving the RPM would jump to 2000 rpm and after about 15 seconds it would drop to 850 rpm and run like it has a race cam in it. I drove the truck last weekend with no problems and then my wife too it, filled the tank...drove it for a few days and then it started doing this. She said it was fine the whole time she was driving it. Any Ideas?

Kevin

 

Check this thread out: https://www.f150online.com/forums/sh...ighlight=P0455

 

Well after about an hour searching the forum for every post related to my p-codes i came across one about the rubber 90 elbow on the back of the intake that goes to the PCV and eureka! there was my problem. It had oil built up to the point where it soften the rubber and caused it to collapse and tear a hole in the elbow. I couldn't hear the leak because it was tucked so far up under the cowl. I took the whole PCV hose assembly out and used a piece of flexfab silicone reinforced hose and ran a complete new line and it fixed her right up. Just goes to show that the search method on the forum does work. Thanks.

Kevin

 

how far on the back of the intake??? i dont see it

 

Trace the large vacumn line from the pcv on or near passenger side valve cover. That line will end at the pcv elbo.

 

Look like that 90 back by the Firewall -

 

Or this when you buy a new one -

 

Or this on the bench - complete (with isolator) -

 

What purpose does the insulator/isolator serve?

 

fixed mine. Well my PCV elbow was the problem it was in bad shape. It came off in 2 pieces. Went to parts store 10$ later truck is running like a new truck But man it was hard to get my hand to the back of the intake manifold!!!

 

Helps keep the lines from freezing/ icing up. Probably why they choose to call it a isolator instead of insulator - just a hunch

 

Well from what i learned from my truck is you got a heated PCV and non heated and that is from the non heated pcv?

 

Nope - I have the cold climate PCV system - It's heated via the coolant line. Look at the line , you can see the heat tube boot on it (pipe on the bench). The very first pick is the whole heated PCV set up - I just have the isolator off to get a pick of the lines themselves .

The Isolator comes on both heated and non-heated. Works to, as cold as gets around here - the IAC has never failed on me from sucking ice out the PCV.

 

howd you guys get yer hands back in there at that thing? i have a 99 5.4 and im getting a lean and i already cleaned the maf.. i dunno how to get my hand in there though

 

I wiggled my long skinny fingers in from the passenger side... Just go by feel... work your fingers along the tube until you hit the elbow...