The car should immediately start to stumble or have a rough idle, right? I'm trying to track down an occassional misfire (car is definitely low on power) and I know OBD-I doesn't track individual cylinder misfires so I figured pulling the plugs would help track it down. I'm not sure how the cylinders are numbered, but so far I've pulled (individually), the front 2 wires on the drivers side, the 4th wire on the drivers side, and the 2nd wire on the pass side and when I start the car with the wire pulled from the plug, it starts right up and idles fine.

What am I doing wrong? Was I somehow just wrong?

Car is a 95 z28 (m6), btw.

 

You do it while it's running. But instead of using the plug wires and burning yourself, use the injector clips. Much easier and safer and you get the same result. Or should I say you should get the same result. The engine should definitely change it's tone and smoothness when you pull one off a running cylinder.

When you pull one and it doesn't change, that's one that hasn't been firing.

Incidentally some of us like to use a IR thermometer on the exhaust manifold to achieve the same thing. The tube that is severally colder than the rest is not firing.

Although the method doesn't work well on the cast iron block type manifolds. Headers are the way to go for this type of test.

 

I've never heard of using the thermometer to test. That makes sense. I have longtubes, so that might be the easiest way to go.

So pulling a wire WHILE the car is running is going to provide a different result than pulling the wire THEN starting the car?

When you say "use the injector clips", what exactly do you mean?

 

Pull the harness connector off the fuel injectors, one cylinder at a time.

 

When you pull a wire, the blm's will climb on the particular bank. Also good to ohm check the wires for opens.