91 sidekick that idles fine, but givin gas, hesitates?

and the check engine light came on. i have had no luck retrieving the code.i have jumped the terminals to retrieve the code, but nothin is happening. i put my timing light on it, and it is doing mostly good fires, but they bounce around maybe a degree, then every 8th or so jumps like 10 or 15 degrees ahead. i have just now put a new distr. cap and rotor on, but it continues to do this. i can smell fuel in the exhaust and think that one cylinder is perhaps not firing? this problem happened instantly, i was out earlier in the day and it was fine when i parked it. any possible answers would be greatly appreciated! thanks!