Ford Repair: 89 escort EEC-IV system, manifold vacuum, vacuum line

Question
i have an 89 escort pony with a cfi. it is running really rough. it will idle fine at first, but soon the injector cuts out a bit and the engine idle plummets then returns to normal. if under load(driving), it doesn't go anywhere over 15 mph, and the same problem occurs, but to a much grander scale. after a little tinkering, i took the vacuum line off the MAP sensor, and unplugged the connectorand it seemed to run fine. any advice?

Answer
Josh,

It sounds as though you might have a bad map sensor. When you unplug it the computer uses a known value to substitute. Also, make sure the vacuum line is not clogged to the map sensor and is free of carbon build up where it goes into the manifold.  It must be able to transfer rapid change of manifold vacuum to the map sensor. These old cars never did idle very smooth even new.  I would try swapping out the map sensor and disconnect the battery to clear the codes.  After you start it allow it to learn the idle.