1997 Bonneville misfire

[zigger21]

I have a problem with Bonneville it comes up with a random misfire and I don't know where to begin, spark plug, wires, egr valve, fuel injector, Oxygen sensor, Vacuum Leak, coil or Ignition Module? I dont want to throw parts at it and hope it works. What is the most common for a P300 misfire code?? Thanks in advance.

[Jfridge92]

Start with the easy things first. How old are the plugs and wires? If they're old, try replacing those first.

Also, I'm assuming your car is an se (non-supercharged?). How many miles are on it, and have the intake gaskets ever been done?

Check for vacuum leaks when the car is cold by spraying some carb cleaner around all the vacuum lines and the intake manifold, if the idle changes you've got a leak.

[human]

Ignition coils are often a culprit. I've had to deal with that on three of the last four cars I've owned. If any of your coils don't have numbers on them, they've probably already been replaced. The factory coils have numbers on them, indicating which cylinders they're connected to. Try replacing the older ones first.

[SuperHbody]

I agree with the coil suggestion. If you're handy with a multimeter you can take resistance readings that can tell you which one is bad as well as test the plug wires. Makes it easier than throwing parts at it.