Occasionally runs rough

My first suspect is a faulty O2 sensor causing the computer to make the engine run rich (too much fuel). This would account for the fouled plugs and rough running. I'm assuming the exhaust smoke is also quite black. This condition will also, unfortunately, quickly ruin the catalytic convertors.

Smoke is not a good sign. Running rough is not a good sign. Oil light not a good sign. You could have a combination of bad things, most likely expensive. Suggest professional help. Smoke can be bad rings or holed piston. Low oil pressure can be bad bearing or oil pump.

Don't know about the speed sensor, but your spark plugs and air filter could be a problem with the black smoke and rough running.

You have a failed head gasket

Major repair

Hope you didn't think the stop leak was
a genie in a bottle,never need any product
in any vehicle,just the proper repair

White smoke was coolant ,should have known that

signs of a bad fuel pressure regulator-- the vehicle will run rough, the engine will not start ( usually in the mornings,) many times engine starts but stalls shortly after starting. a bad regulator can result in fouled plugs. replacement is only cure. 1- black soot on plugs-2-black smoke from tailpipe-3- running rough-4- stalling, good-day! repost if need be.

A bad coolant temp sensor for the ECM will cause that problem ... they are cheap and easy to replace. One other possibility is a piece of carbon stuck in the EGR causing an internal vacuum leak ..
Good luck.

Hello and welcome to FixYa!

White smoke visible on the tailpipe? As a first course of action, I strongly suggest that you have an engine tune up, replace the spark plugs and fuel filter as well. This will surely give better fuel burning, rough idle and bad smell can be eliminated.

Hope this helps and thank you for using FixYa! Have a good one!

Upstream o2 sensor. Regap spark plugs to spec

Sounds like bad injectors, bad O2 sensors, and or too much fuel psi. Check the fuel psi against what the service manual says. If the fuel psi is too high, your regulator is bad. If the fuel psi checks out ok, you likely have a bad O2 or bad fuel injector(s).

Have you taken a spark plug out yet? You may have fowled them out. if they are not clean and have a whitish tone to them, then they need to be replaced.