i have a 1997 f150 and it is running three codes, 2 of which are about the bank 1/2 running lean. i checked the oxygen sensors and they are working properly.
it is running a third for a evap system.

the 4x4 doesnt do anything at all, if you start it, and then turn the switch, it's as if nothing happened. if you turn the ignition "on" but not running, it will show on the dash whatever is selected, and stay that way even after you start it, but will not change after the engine is started, and does not affect the 4x4. i checked the four hoses going into the pumps behind the battery, 3/4 do nothing, one has a constant suction (the one that plugs into the pump toward the engine on top).

everything worked and when i checked the hoses the windshield wipers stopped working?

what all on this vehicle runs off vacuum, and what all runs off the engine's vacuum? does the 4x4 run off engine vacuum in any way? and any good ways to test for leaks?

does this make sense to anyone? if you can shed some light on the situation i would greatly appreciate it.

its a 97 f-150 super crew. with a 4.6.

 

i did want to add i have looked on the site and researched, i will check into the elbow a the back of the engine. any other ideas? thanks again

 

Vacuum leak. Check the PCV system first.

 

would you happen to have a diagram? i will check here in a few, thanks again!

 

Vacuum diagram label was put somewhere under the hood, usually on the radiator support, valve cover, or underside of the hood when the truck was made. See if it still there.

 

i dont see the diagram, but i did find a box under the passenger fender, not sure what its for but has two hoses going to it, and what looks like a disintegrated piece of hose, this isnt another reservoir is it? i found the two behind the battery, i covered the two hoses and no more leak, engine runs better have to clear the codes and check again.

i have checked the 4x4, the front axle engages/disengages as it should now when the switch is selected, but the transfer case motor isnt working.

i removed it and checked it with a 12v battery, and it works.
but when on the truck, nothing happens.


here is what it does with the 4x4 lights.

when the truck is off(key on) i can turn it to 4x4 or low, and it lights up in the dash, but as soon as it starts, it will not change from whatever is selected, and it doesnt activate the transfer case motor(while removed from the case). i have to turn it off, switch it again, and restart it for the lights to go away.

i have checked the 8 relays under the "oval" dash piece and all under the hood stuff. there was a 20 amp fuse blown in the real little fuse box in the corner that has two fuses, changed that, still nothing. (i dont know what any of these go to, cant find a diagram) but all fuses and relays are good.

when i switch the 4x4 switch, people say i am to hear a relay click, but nothing happens, do keep in mind the actuator on the front axle works as it should when i change the selection.

i can manually switch it into 4H with the transfer case motor off, and seems to be in 4x4. but nothing from the motor.

does the motor have a sensor or anything in it that could be bad, for me to be able activate the motor (with the two wires going to the motor). there is wires going into the back of the module but i assume that's to turn the motor off when it reaches its place or tell the truck if its in 4x4 or not.

any ideas? t

thanks again!

 

also wanted to mention it isnt running any codes for any of the things like "short circuit to T-case motor" etc.

is there a vacuum line or sensor running to the transfer case, or is it just this one thing? that box i speak of in the fender was busted, said vac on the side of it, when i say i blocked the hoses off i put tape over the two so i would be able to hear/find any other leaks.