had the same exact thing on my 87 ranger 2.9 the cats are full split it at the flange and pull the exhaust back should notice a differance right away other than being really loud. I chased mine for about 3 months finally found it when all it would do was idle

 

i have a similar problam my 87 ranger with a 2.9 i have replaced both the fuel pumps and filters and cleaned the injectors and it will run great 99% of the time but every now and then i will get in the truck in the morning and it will run like crap it dies at lights and coughs and smokes and the next day i will get in it and it runs great

 

Another thing that needs to be checked are all the ground connections on the harness.

 

I know this is old thread but,,, my '88 BII was doing same things. I changed and/or cleaned all sensors, O2, good tune-up, cap, wires, plugs, timed, CEL stayed on even trying to et codes with analizer,,, noting!!. come to find out it was the EEC-IV computor was bad. seems there was dampness down in carpet/kickpad by computor and the wiring was wet. put in new one,, fierd right up, running smooth and had a code 41 on scanner then,,O2 sensor lean code book says.. Also, make sure all the ground wires making good contact,, theres probably5-6 in engine bay and under dash. mines like that. you might try this,,good luck,,, cant hurt. Larry

 

Ok this might work try replacing your fuel pump and screen as well as your fuel filter as in most of the posting i have read no one has done this. Also air/plp connected to the side of the fuel injection system but that also may need to be replaced. Also there is a in line fuel filter running from the injectors try replacing that also the injectors their self may need to be cleaned

 

Folks, it's nice to try to help but this thread is almost 4 years old, The OP has long since moved on, hasn't posted here since April of '08.

 

i don't know if you got your answer already or not yet, but my truck was doing similar things, and i was told to check my coolant temp sensor, mine happened to be half off and full of water...so i changed that and din't fix it but it ran better, then i was told to change the eec relay and fuel pump relay. did that and she runs great. so id change the relays, 10 bucks each, the relays r the same to, interchangable.