incomplete combustion, Rough idle,

[chemdoc76]

Hi.

I just bought 87 ranger 2.3l. First, I've noticed lack of power when I turned 9o' turn or after 2nd gear shift. I checked the spark plug and it was black with carbon deposit. I changed spark plug and the wire. the previous owner changed distributor already.

After the replacement, it seemed better and after a few days later it started again. I opened distributor cap and the wire connection wasn't matching with the manual so I changed, it didn';t start. I put them back to original position and it works. I turned 1 cylinder to TDC and looked the rotor and re-positioned the wire connection. it didn't fire up. I put them back to original position and works.

I checked the spark by pulling out the wire from spark and looks like electric spark has no problem.
now, the truck is hard to start. I have to put some gas to start and the idle is rough. it's like periodically stalling and starting again.

I was thinking to change TFI module. but people say TFI module fails when it's hot.
I need someone to guide me to the right direction to fix this truck...