Dear Tom and Ray:

I have a question that might involve automotive espionage. Last Saturday, my wife and I were awakened by a very loud explosion that shook our upstairs windows -- we thought someone had bombed our neighborhood. We investigated to find everyone crowded around a neighbor's old Ford Bronco. Evidently, when my neighbor started his car, the entire muffler system exploded, leaving a pile of debris surrounding the vehicle. I've never heard of a muffler going up in smithereens like that. I do know, however, that this neighbor is in a virtual hatefest with another neighbor -- a former Navy Seal -- and I know that this other neighbor has been hoping for an opportunity for revenge for a previous insult. Is it possible that the muffler just went up in spontaneous combustion -- much like the drummers in the rock group Spinal Tap -- or do you think that this was the result of some nefarious human act? We believe it was the latter. My wife and I are dying to know. -- Randy

RAY: I suspect that you guys are right, Randy. This has all the markings of an I.E.D.: an Irate Ex-military Dirty-trick.

TOM: It is possible for a muffler to explode. For instance, if your spark is interrupted, or if the spark plugs aren't creating enough spark to start the car, unburned gasoline can collect in the exhaust system. And then, when the car finally does start, that unburned gas can ignite.

RAY: This is commonly known as a backfire. And it can be severe enough to blow a hole in the muffler or to blow a weakened muffler right off the car. But when that happens and you examine the muffler, what you usually see is a gash -- a 4- or 6-inch opening where the muffler's metal seam has separated. I've never seen pieces of the muffler distributed around the car.

TOM: So I'm guessing the Navy Seal calculated very carefully, and put just enough explosive under the car to scare the hell out of this guy without actually maiming him.

RAY: Or maybe he miscalculated, and only blew up the muffler.

TOM: In any case, the lesson here is: Don't start a feud with your neighbor if he's a former Navy Seal. And I hope the neighbor with the Bronco is smart enough to leave the investigation of this to the proper authorities and not take it upon himself to escalate this feud any further. After all, these guys are underwater-demolition experts. You don't want the next explosion to take place while you're sitting on the throne doing the crossword puzzle.