Well right in the area where he dropped that plug, and where it would be stuck at, is what is called a knock sensor. Now a knock sensor does two things, 1) it senses harmonics and vibration frequencies of an engine and determines what to be normal, any sort of sound frequency not in synchronization with what has been determined to be the "norm" is translated to pre-detonation. In an engine cycle pre-detination is what occurs when one develops hot spots or something during the ignition sequence isn't right. And the result is the combustion chamber firing before the piston reaches TDC, or top dead center. 2) after interpreting the uncommon sound frequencies into an electrical signal it sends that information to your PCM, which then the PCM in turn retards your timing as a safegaurd to ensure that the motor doesn't blow completely, thus robbing you of horsepower and fuel efficiency due to lack of timing which basically causes the engine to operate at a lower HP/TQ level. Because instead of the spark plug firing prior to your piston reaching TDC, which is called advanced timing, the computer delays this and fires it after the piston reaches TDC(or later in the combustion sequence) during the downstroke, meaning the resulting combustion will be weaker due to the fact that the air/fuel mixture will be less compressed during ignition.

So it doesn't really matter that it's not happening in the combustion chamber, the knock sensor will pick the sound of the plug vibrating against the engine block and determine it to be pre-detonation. This is what we refer to as "false knock", now false knock can come from a variety of things, from loose bolts, to worn engine mounts, to transmissions. In this case a dropped plug resting on the engine block and the transmission clutch pack housing.

Make sense?

 

Makes lots of sense, you never know when you need info like that? It's good to know that if I ever run into or know someone who ever has that happen and tell them what you just said. I would probably get the "wtf do you know look"! Thanks for the explanation........

 

You'd be surprised at the things that would effect the way an engine runs nowadays

 

Doesn't sound stupid to me at all, when I first read it, I was somewhat confused too. But then I recalled an article I read on KR, and it made total sense. If it were down there, laying up against the block close enough to the knock sensor on the rear bank of cylinders, the vibrations could cause the ECU to misinterpret the vibrations as knock. Therefore retarding the timing to compensate. Correct me if I am wrong on this PacerSS

 

Wow, by the time I got done writing that last reply, you guys had already posted three more responses.

 

Here's a good image of where the knock sensor is located. It's right behind the metal shroud on the side of the block. Now in this pic the transmission is removed. But normally the long part of the clutch pack and diff housing seen in the bottom pic is in the way and sits probably 3/4" away from the block. As it wraps around the backside of the engine.

 

The ECM can pull as much as 10 degrees of timing if not more with some thing just rattling against the engine.That will put a dent in power an even make it run rough

 

Same here

 

Haha much easier way to explain it. I should have went that route.

 

That it did when I first fired it up. I was pretty damn concerned. But like I said, since the thing fell out, running great.