ok so i have a bone stock 2001 f150 with 87000 miles on it i was on my way back from a camping trip and my check engine light came on so when i got home i checked the code and it came up as p1151 it seems to run ok other than at an idle it will stumble just a little bit and it seems to idle a little bit high im thinking its a vac leak but im not sure any ideas?

 

O2 sensor or vacuum leak. Check all of your pcv lines, especially running to the back of the throttle body/intake. They are known for cracking. Check pcv valve if its functioning properly.

 

checked all the vac lines i could find even sprayed brake clean all over hopen i could find a hole and get it to stumble think im going to try the drivers side front 02 sensor

 

The elbow (90) that is common to crack, wouldnt be in an area where you can see it. You have to follow it around with your hands to the back of the throttle body and feel for any cracks. Brake cleaner wouldnt do much if sprayed in that area considering its pretty well hidden. I would check it one more time. If you can... twist and pull on it to remove it from the back so you can visually inspect it. It just comes off, but since it hasnt been removed.. like any other hose, a good twist and a few pulls will take it off. It is a very tight area though, good luck.

 

the PCV elbow that Toyz is describing seems to be the most common place to find a vacuum leak on these engines. It is VERY common to find it cracked. get a new one from the dealer and also a new pcv valve (aftermarket pcv valves are no good on these engines). even if it isn't leaking, it may be a good time to replace at least the valve if it's never been done before.

 

is that at the back of the throttle body or at the back of the plasic intake plenium?

 

ok so i pulled the elbow off the back witch was connected to the tube that follows around to the pcv and visually it looks good im going to pull the pcv and check it probably replace it for good measure but that still leaves me stumped and still possibly leaning towards that 02 sensor being bad does that sound about right?

 

P1151 Lack Of HO2S21 Switch - Sensor Indicates Lean

Sounds like you found the right elbow

Its more common for a vacuum leak to cause this CEL but not impossible for it to be a bad 02 sensor. If you feel that you have expressed all options as far as hunting down a vacuum leak which could be anywhere from the throttle body gasket, elbow gasket, pcv line, intake tube and a few other places then I would suspect the 02 sensor. Just tough to think one went bad at 87k but its not impossible.

Maybe someone else can shed some light on a possible cause while I