1992 B2200 running rough

Hey everyone.

This is my first post, so if I have posted this in the wrong section, or have not explained myself on any of the following let me know!

So, I have a 1992 Mazda B2200.

It's been running rough for the past couple of months.

It was idling very poorly

The truck is currently running on 3 out of 4 cylinders

The #2 cylinder is receiving spark, but upon pulling the spark plug wire off while running, there is no change in the idle. Yet pulling #1, 3, and 4's plug wires while running the truck will either die or idle extremely roughly.

We have tried;

- changing the distributor cap and rotor
- changing all spark plugs
- changing all spark plug wires
- adjusting the idle
- adjusting the timing
- tightening the valves to specs (0.007 on intake, 0.009 on exhaust)

So basically my truck is running on 3 out of 4 cylinders, and is idling very roughly.

Well I guess you have your answer, running on 25% of the cylinders will make it run rough.

Does this truck have an EFI or carb setup.
Did you check for vacuum leaks on the lines near #2?

Haha, yes that is my problem.

But my question is why has this happened?

This truck is fuel injected.
I didn't notice a vacuum line designated to the #2 cylinder, but will have a look, thanks.

Perform a compression check. If that is good, see if you can move the fuel injectors around, swap the #2 fuel injector with any other. If the dead cylinder follows the fuel injector, then the injector is plugged or otherwise not working, if it does not, it could be a wiring issue. If the compression is low in that cylinder, then there is some internal problem in the motor.

Don't forget to check wiring harness voltage at the injector connector before moving injectors.