help xj running like crap

please help my cherokee is running on the outter four cyl. it has a 4.ol and is a 89. it has spark, compression, fuel. i dont know whats wrong with the 2 middle cyls. if you know or its happened to you please help. also i drove it last fri and it was great left for weekend started monday and now runs like crap. help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Is it flooded? Is there black smoke? - Could be MAP sensor vaccum connection.
Distributor cap and wires really old?

Sounds like the dist. cap. Even though you are getting fire, it may be at the wrong time due to graphite dust or moisture in the cap. Or maybe somebody don't like you and switched the two wires. It could happen......