Where would I start to look for a vac leak, My air control can be set on vent from defrost and you sometimes have to let off the gas before it goes to vent, and it sometimes goes back and forth.

 

do you have a vacuum leak or do you have a heater problem?

size motor? 2 or 4 wheel drive?

 

Sounds like a vacuum leak to me. Best thing to do is search this forum for vacuum leak. There are tons of posts where people tell where they found there leak. There's a few common areas.

 

pass side near the manifold has a bunch of vacuum lines, and under the back of the drivers door is the charcoal canister, i had a leak there.

 

Cheat,

Look in those posts that we were working on. In there, I have listed where to check for vac leaks. Use a vac pump to pump down each section at a time until you find it.

Brake booster circuit is one. Then, the manifold TB line that feeds the vents. There's a check valve there so, it's easy to identify. There's a line that goes down underneath the vehicle that feeds the tranny. Remove that from the T and pump it down. There's also one that may or may not run under the battery compartment for your year. You have a newer truck so, I am not sure.

Next, you will have lines that feed your axles if you have 4WD. Then, you may have a IAC motor gasket leak. Remove and check for dry rot or dimpling, crushed o-ring there. R&R as needed. Lightly grease the new one and place on the IAT and make sure it seats into the TB before tightening.

Also, check your injector o-rings, your PCV valve assembly and the hose the feeds the intake.

Check for a leaky TB shaft. It may also be under / inside the dash as part of the venting system.

You may have an intake leak at the gasket interface between the heads.

In all cases, use a length of rubber hose up to your ear and start probing around or, you can simply pull vac on it with a vac pump.

Start there.

 

Well my dad done the 3 key trick because it has a cell. he said something about the charcol canister, Can you explain how you fixed your leak there?

 

There's two parts of what is called the evap emissions system. This includes the purge valve solenoid and the canister under the vehicle. What is involved there is two lines that attach to the purge solenoid. One is the main feed while the other is the thru feed that goes down to the canister.

Check the rubber boot at the canister first for dry rot or a tear out. If that checks out, check the main feed from the intake to the PS. Remove the end from the PS and plug it. Remove the main end from the TB and pump it down. If that checks out, proceed to checking the thru feed. Plug both ends of the main feed line. Disconnect the line from the canister and plug it. Now pump down the thru feed that goes into the canister. If that passes, check your canister for cracks, gross defect. If none is visible, remove the plug from the boot and place it back onto the canister. Now pump the line down. If it leaks, your canister is the problem. If not, it's the purge solenoid diaphragm or the duty cycle solenoid (depending on the year)

At least your getting a CEL which helps to narrow it down. I replaced mine before it got to that point.

 

the charcoal canister looks like a big can of soda FYI, located under drivers door.

my boot ws dry rotted. the line goes way up to the engine bay, so i cut the line, shove something in it, so i could clamp down a new section of hose instead of doing the whole thing.