The list of possibilities is long. These may shorten that list.
If you think it's ignition related:
> Connect a timing light to each plug wire and watch for a steady uninterrupted flash. If you notice one is erratic check it's connection at the coil for corrosion. Make sure it connects tight. All is well? Test the coil. Here's how:
http://www.autozone.com/az/cds/en_us...rInfoPages.htm If the coil is good make sure the PCM connection is clean and tight.
Fuel related?:
> Buy a mechanics stethoscope ($15), touch it to each fuel injector and listen for a steady click. Might be able to feel it.
http://www.autozone.com/az/cds/en_us...rInfoPages.htm If one skips, make sure it's connection is clean and tight then measure it's resistance (around 12 ohms). If it's much off from that (compare to others) change the injector. You can connect an injector test light at each injector connector to verify steady voltage from the PCM.
> Connect a fuel pressure gauge at the fuel rail test port to verify steady pressure (50 psi).
Other stuff:
> Clean the throttle body (TB) and idle air control valve (IAC).
http://www.autozone.com/az/cds/en_us...rInfoPages.htm How? Disconnect the main 3 inch diameter air duct from the TB. You'll see the throttle plate in the TB. Spray the area with a TB cleaner. Also spray the small opening for the IAC valve port.
> Pour a can or two of fuel system cleaner the next couple times you fill up.
> Gonna be a small one but look for a vacuum leak. Inspect all the vacuum tubing under the hood for cracks. With the engine idling spray the base of the intake manifold with brake cleaner. If you hear the idle change, you need an intake manifold gasket. The liquid temporarily blocks the leak and returns normal vacuum pressure.
> Normally I'd say do it but, in your case I'll say it wouldn't hurt to get a load test on the battery. Long shot but, there is a slight chance it could be effecting this.
> See a service engine soon light?
> PCM = Powertrain Control Module located next to the battery on the fenderwall.
> These links are for a 99 but your's should be simular. Recommend you buy a maintenance manual ($15/20) or subscribe to a manual at Alldata.com ($15) if you're planning on getting up to your eyeballs in this. Keep in touch.