If you have an induction type strobe timing light, just clip the pick-up
to the suspected wire and you will see immediately if the there is spark
to the plug. If you have a known good wire and spark plug, then replace
then install a new rotor and distributor cap.  Even if you have bad
valves and rings, if that plug is firing, you will get something = some
kind of reaction to removing the wire. If with new rotor, dist. cap, new
wire and plug, you still don't get action, then pull and test the
injectors for that side of the engine. Be sure the FI is firing for that
cylinder. It is eithro or - ignition or fuel.

Good luck.

Regards,

John Rodgers
88 GL Driver

craig cowan wrote:
> Hello again. I had my engine timed with the help of a local guy whos
> good with timing, and it was running great. Then suddenly it started
> to sound "strange". We tracked the problem to an exaust leak, and the
> sound is normal for an exaust leak. However, we wanted to rule out
> that one of the cylinders wasnt firing, so while selectively removing
> the plug wires from the cap, we noticed that removing the wire from
> cylinder 4, there is no change in the way the engine runs. If any
> other wire is removed, the engine imediately runs poorly. This would
> make it seem that cylinder 4 is not running. We've switched wires
> between working cylinders, spark plugs, and a new rotor. With the plug
> removed turning the engine over, theres compression in that cylinder.
> We dont have a compression guage yet, but we know its enough to pop
> your finger out of the hole. Yet, it seems to not be running. Last
> thought is that the Cap is bad for that cylinder? I will try to get a
> new cap and see if that fixes things. Any sugestions on what to check
> would be great.
>
> PS: I believe it ran on all 4 before it was re-timed.
>
> -Craig Cowan
> '85GL Sunroof
>
>