OK, here's a little bit of working theory that'll help you to see the ‘why’ of the Noid light test.
Whether you're testing a No Start Condition or a Misfire Condition, you'll need to know if the cause of the problem is a lack of fuel. When your GM 3.8L (Buick, Chevrolet, Oldsmobile, Pontiac) does not start, it will be either because of a lack of fuel or spark. The same thing goes for when your GM 3.8L equipped car or mini-van is misfiring... that specific engine cylinder isn't contributing to engine power because it either lacks fuel or spark.
Now, since the above two conditions (No Start and Misfire) can be caused by any number of things... one of the things that has to be eliminated, from this list of possibles, is the fuel injector not getting power or the injector pulse signal (On/Off switching signal) from the vehicle's Computer.
This is where the fuel injector Noid light test comes in handy, because you're able to visually see if both of these signals are present or not. If no flashes, then now you know that you have to verify that the connector is getting power (12 Volts) and the injector pulse signal.
One thing to keep in mind, is that the fuel injector Noid light test does not test for a BAD fuel injector. But, is the first step in verifying if the fuel injector is BAD or not. For the fuel injector test tutorial, go down to the list of links at the end of this article.
There are lot of fuel injector Noid light sets to choose from and many places to buy them. I'm gonna' make two recommendations to you:
1) Which one to buy: The fuel injector Noid light kit that I recommend is the Performance Tool NOID and IAC Light Set - 10-Pc. Set, Model# W89501 Noid light set, and here some reasons why:
2) Where to buy: All of the auto parts stores in your neighborhood sell a fuel injector Noid light set... but at double or triple the price. If you want to save some bucks, you can go to the ads above and shop for them there.
Now, if the Noid light tests on your Chevy (or Buick or Olds or Pontiac) indicated that everything is OK, and yet the car or mini-van is still misfiring... the following articles might help:
“Remember, this hobby is supposed to be your therapy, not the reason you need therapy.”