XJwonders

I have a 1999 with 4.0/ax15 (5 speed manual trans). Here's what happened. I decided to fix the crack on the exhaust header at where it always cracked, I had a clean intake manifold, a set of 784's, and a bored throttle body so I figured while I had everything off to weld the crack, I can install the new components at same time.

Disconnected the battery and had the ground clamp of the welder 5 inches away from the crack, so that way there won't be any current traveling far from the weld.

After welding the crack, I went ahead and installed the intake, injectors, and the throttle body, (using the sensors off the old TB).

Two weeks later, I noticed the engine was very slightly hesitating once in a while when I shifted into fourth gear. Not any other gears.

Few weeks later, it started to hesitate whenever I would shift into third, fourth, or fifth gears.

About a month, it would start hesitating any time I changed gears. And later on eventually it started to hesitate and stumbling very slightly whenever I'm just driving, not when I'm changing gears.

Right now it got to the point that it's annoying to have the engine hesitating and stumbling more often and for few seconds longer.

I decided to test the TPS, I inserted a single strand of copper wire into middle terminal and plugged it in, with key on, using my multimeter, I got no voltage. (Red to copper wire and black to battery ground)
Next I wanted to see if the sensor was getting voltage, so I put the red probe to the pin #3 with black probe to battery negative. I got 0.01 volts.

I'm stumped now. All engine grounds are cleaned twice. No trouble codes either.