Volvo: 1996 Volvo 960, vacuum leaks, 1996 volvo 960

Question
My Volvo started running like it was missing a cylinder or
two. So I replaced the spark plugs and it is still
happening. How do I test my coils to see if they are the
problem. My wiring harness looks bad but it has looked bad
for a few years. If I have to replace that, how much is
involved with that? Any answers that you have would be
greatly appreciated. Thank you......

Answer
Scott,
Move the coils to a different cylinder and see if the fault codes follow. Or replace the coils. Do a compression test to be sure that you do not have a weak cylinder. Make sure that you do not have any vacuum leaks especially the intake manifold. You could pull all the plugs and attach the coils crank the engine watch to see if the plugs fire.