We got our son a 1999 2.5L ranger with 142,000 miles. It ran ok but idled a little rough. Started with air filter and pvc valve: little better. Next used some MAF cleaner: not a lot of change, Next changed passenger side plugs/wires and sprayed carb cleaner in throttle body, disconnected batt and restarted: ran rough at first then settled down, still a little rough idle. Went to take off the IAC and broke a bolt, took off throttle body(calling it that) and drilled out bolt, since it was half way apart, took upper intake off and changed dr side plugs and wires. Put it back together and runs worse than ever, runs really rough when you start it(every time you start it) then settles down somewhat but has really no power when you get on it going down the road. Plan is to take all plugs back out and check gaps and wire resistance. Did notice that when I take the vacuum line off of the EGR valve nothing happens, no change. Any thoughts, he gets his license Friday and would like it running?

 

the egr valve diaprahm may be plugged in the open position by carbon deposits

i used to clean those egr valves, but now i just replace them with new ones

also check the vacuum hose leading from the vacuum solenoid , the older ones have a habit of sticking open allowing constant vacuum to the EGR valve

 

a carbon clogged catalytic converter can cause or aggravate these problems; you might check at the tailpipe for smutty emissions or weak pressure.
fuel filter is also something you want to test; wear eye protection.

 

good call