I have a 97 Honda civic an ive been having the same problem over an over an cant figure out whats going on. the car is running like crap an getting terrible gas mileage, all cylinders are firing except cylinder 4. ive replaced all wires, sparks plugs, dis cap, mass air flow sensor, took the injectors out an cleaned them, an the car is still not firing on cylinder, please help.

 

Compression test this engine. Based on the results, a leakdown test may be required.

How did that old spark plug in cylinder 4 look when you replaced it?