I've been get 1131 and 1151 lean codes bank 1 and 2 for a good amount of time now. Replace All gaskets from intake manifold and up. The classic aluminum crossover leak was happening on my intake manifold I sealed it with gasket sealer and it worked. Right now it must have a very tiny leak because a small amount of coolant leaked from it over time maybe 8oz in 2 months. I don't think a leak in the cooling system would cause any type of vacuum leaks or non metered air coming in. Any input?

 

You may have already seen this (what the shop manual says about P1130)--work the "possible causes" list from the top down, focus on things that would affect both banks...

 

if you find what was causing the problem please post it back on here because i'm throwing those 2 codes also.

 

I wonder why its not throwing a p0171 and p0174 as well...

I would check all the vacuum lines, especially the one that runs straight to the back side of the intake elbow, they corrode and break apart very easily. IF you just touch them they leave black crap all over your fingers. Also check all the little red and green hard plastic lines and the rubber nipples. Did you try idling the engine and spray some carb cleaner around the intake manifold/elbow area to listen to increases in RPM?

 

my car has an EGR delete, so those red and green hoses are not connected to anything, but they ARE capped and sealed well. I've sprayed carb cleaner around the ends of them and there is no leak there. I haven't checked the ones off the back of the plenum yet tho. also my PCV valve had a little oil leaking around there so that's where I thought a leak could be coming from so i replaced it but it didn't help. i can clearly hear a hissing when its under a small load, but at idle and full throttle (any rpm) you can hear it go away.

 

my car throws a lean code every so often after the header install

 

i just picked up a new intake manifold from ford racing...im installing it tonight and hopefully the codes will stop along with the coolant leak

 

So far I havent thrown any codes, i hope that fixed the problem

 

What mods have you done to your car?

 

does anybody have advice as to why i would be hearing a hissing which sounds like a vacuum leak only at mid load or so? it clearly goes away under full throttle and no throttle, but in that mid point there's clearly a leak.