Check the wires using an ohmmeter or DVM, measure the resistance of each spark plug wire. They should be about 2000 ohms per foot of length. A 2 foot wire would be 4000 ohms, a 3 foot wire would be 6000 ohms.
Do the light show thing too. Wait until dark and then open the hood and start the engine. Look closely at the spark plug wires to see if there is any glow or flashover.
Do a cylinder balance test to spot weak cylinders. Dump the codes while you are at it.
Cylinder balance test:
Warm the car's engine up to normal operating temperature. Use a jumper wire or paper clip to put the computer into test mode. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about 1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 99 for everything OK, or the number of the failing cylinder such as 22 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures. Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure
Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.
for more descriptive help
For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153
for what a typical hand scanner looks like. Normal retail price is about $30 or so at Walmart.
Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829
– It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $33.