well after about a year of setting with a blown motor i found a good deal on a motor out of a 2000 with 130,000 miles on it so i pulled the ole goat in the shop and did my motor swap fired right up, broke the crank shaft sensor during swap tho so im about to change that, but my problem i cant figure out it the 4wd. never really had any issuse with 4wd so i havnt ever had the chance to learn it, but when i put it in 4wd the front akle shaft starts spining but the front axle does not engage, i no this for sure on the fact that my rear driveshaft is mia lol. still trying to find one, im asumming i have a vacuam problem some were but not sure wear. i have noticed ther is a green vacuam line at the back of the motor that looks like it should be hooked up to somthing or mybe a vent, idk. any help is appreciated

 

Two lines at the back of the motor. White is source vacuum. Make sure that one is hooked up somewhere.... green is indeed a vent.

Two lines at CAD on front axle. In 2wd, outboard port (closest to passenger tire) should have vacuum, in 4wd, inboard port should have vacuum. Check those first.

 

just cheaked the lines in 4wd and it had vacuum in the line it should have it in, so im thinking mybe theres a problem in the motor or plunger on the axle?

o and btw just pulled the crankshaft sensor on the back of the motor the one inbetween the motor an tranny and it wasnt broke, could it be out or could it be somthing else. its running rough and back fireing real bad

 

If you have a new one to try, (crank sensor) give it a shot anyway......

Prolly have to pull the cad housing off, and see if things will move by hand.

 

on that crank sensor it back fires in a rythem and lopes like it has a BIG cam in it but its all stock and i put my other pcm on that come on my truck factory and all its throwing is o2 codes, yet the pcm that cam with my motor throws a crankshaft sensor code i dont have my down stream (after the cat) o2 sensor in becouse i dont have the bung welded in so i can put one in it and it never ran this bad, could it be somthing as simple as the 02 sensor?

and im gonna pull the cad housing off after i get a bite to eat ill keep yall posted

 

Disconnect the pre-cat sensor, and see if it runs any better/worse.

 

un pluged it and it dont help or hurt it still runns like crap and back fires.

took the houseing of the 4x4 and put it in 4wd by hand gonna clean the houseing really good put it back on tonight see how it goes

 

Check and see if you got some wires pinched between the engine and trans. Cam and crank sensor harnesses are both back there.

Did you try the new crank sensor? If so, where did you get it? (what brand?)

 

i think im gonna try a new down stream o2 sensor, my buddy said he had the same problem i have with his 96 2wd with it running rough and back firing and he changed his o2s and it fixed it

 

Disconnecting the front O2 prevents the truck from going into closed loop, thus, the pcm runs off tables, and completely ignores BOTH O2 sensors. If they are old, yeah, replace them on general principles, but, don't expect it to fix your issue.