today just for the heck of it i decided to swap computers from my parts truck 87 to my 88 and see if it made a difference in anything. well not much was different except that after a drive around town i noticed the check engine light flashing on and off i figured this must be a check code in memory from the 87 so i decided to erase the memory codes and run it like that well the check engine light kept flashing and after checking the codes it came back with 31 and 84 which have to do with the EGR valve now im curious here the EGR is different on these two trucks in fact im not even sure where it is located on the 88 but i can plainly see it on the 87 is my computer on the 88 truck bad and not picking up this sensor or is the 87 not compatable with the 88 and is freaking out because the EGR is different i even cleared the memory codes on the 87 again just to make sure and it still came popping up with the same codes is my EGR bad cuz my truck does have a rough idle which ive been trying to pinpoint for almost a year now with no luck. the hayes repair manual is absoultly no help at all it shows detailed breakdown of the 2.8 motor with the carb but is so vague on the 2.9 fuel injected motor. if anyone knows anything about this or can steer me in a direction i would apreciate it
Steve

 

The reason the computer is reading this is that the 88 model does not have an EGR, they quit putting them on in 87. The only reason I know this is that I have a 90 model, last year it started idleing between 500 to a 1000 RPM's just back and forth. I took it to my Ford dealership and they found the spring in the EGR was broke, so they blocked it off for me and told me that the motor in mine was an 87 or older because they quit putting them in in 87 they told me they could put a new EGR on but they would have to hook up new electric and I would have to get a computer for an 87 model instead of the one for the 90 model.