i recently bought a 1988 mazda rx7 but it misfires at cruising speeds never during acceleration it has sparkplugs and wires and ive replaced 2 of the 3 coils im replacing the 3rd soon plz help becuase i like the car alot and want 2 get it running good

 

Not sure what you mean by "three" coils as the car has a leading coil and a trailing coil. As far as the missfiring is concerned does it occur only when you are decelerating. If so, the likely causes would be either a misadjusted TPS or a problem with the Anti Afterburn valve located inside the ACV. Make sure the Green/Red wire at the three wire TPS plug reads 1 volt w/key to on after the car has been driven for 20 minutes or so. If it doesn't read 1 volt then locate the TPS adjustment screw which is surrounded by a spring on the front of the throttle body as it is part of the throttle linkage and screw it till you get the multimeter to read 1 volt on the G/R wire.

 

during deceleration it isnt so bad either just when cruising and yes ur right about the leading and trailing coil but one f them has 2 seperate coils on the mounting bracket

 

Completely agree with this, also while your at it check to make sure the sweep through the voltage range is good when opening and closing the throttle, no crazy spikes or drops as you do it. Also, Banzai Racing offers a TPS tester (http://www.banzai-racing.com/store/TPS_tester.html#18)