His finger moved to the bottom of the drawing: .
He circled a lump in the diagram. "See that? The distributor. But by late '90s, it's got a cam position sensor underneath. No rotor. Kids today don't know the joy of setting timing by ear."
Finally, the top: .
He slid his finger up a set of vertical lines: .
"Front bank: 1-2-3. Rear bank: 4-5-6. Firing order is 1-2-3-4-5-6. Wait—no, that's wrong." He squinted. "1-2-3-4-5-6? Hell no. It's 1-6-5-4-3-2. That’s right. GM’s oddball. Makes it sound like a tractor with a cold."
"Sequential fuel injection, not batch-fire. So the diagram shows six little squares—those are the injectors, one per cylinder. The fuel rail runs right across the top like a silver spine. And that round thing on the front? EGR valve. Clogs up constantly."
I can’t generate an actual diagram image, but I can tell you a story that walks you through one—as if a grizzled mechanic named Frank were tracing it with his grease-stained finger on a torn page of a 2004 service manual. Frank pulled the faded diagram out from under a pile of oil filters. "Chevy 3.1L V6," he muttered. "The little engine that wouldn't die—until the intake gaskets did."
"Right here. Plastic frame with silicone beads. They'd shrink, pull away, and suck coolant into the oil. Milky sludge. Customer says 'my heat don't work.' You pull the dipstick and it looks like a chocolate milkshake. That's the 3.1's trademark."
"This is your rotating assembly. Cast-iron crank, six pistons—three on each bank. Odd-fire? Nope. Even-fire 90-degree V6, so it shakes a little less than the old 2.8L."
His finger rested on the two most notorious parts: .