Last week I posted about my UIM gasket failure. My father replaced the plenum and gasket, but did not do the lowers.

For 400 miles, the car ran outstanding. Then a couple days ago I pulled out of my driveway, went about 600 feet, and hit the gas to turn out of my sub. The car had *very* little power and started knocking pretty loud. I turned around and drove it back home. Total distance driven less than a half mile.

Checked the coolant, and checked the oil, all okay. Pulled the plugs and cranked it over, just gas came out, so that'* good. Started it a couple times and the knock is definitely loud, sounds like more towards the rear of the engine but hard to be sure.

After a couple hours, I started it again, this time the knock was only about half as loud, and over the course of 1 minute or so, it completely went away. So I drove it around (about 15 miles) and it'* running perfectly again.

A friend'* cousin who is a GM tech says it sounds like the ignition control module. Says they randomly fail, then work okay for a while, then fail, etc. Plugs are new, plug wires look okay, does this sound like a reasonable thing to try? Because right now it runs awesome and how does one go about fixing that? But I have a newborn and if I can't trust the car, in traffic, etc, then I'm not comfortable driving it.

No CEL or codes that I know of, but I can't scan the car myself since it'* ODBII connector with the ODBI guts.

So let'* hear what everyone thinks!

first of all if it was a mechanical knock it wouldn't just go away so you may be safe there.
I'm thinking a valve was hanging up or you have an ignition issue.
Dirt and antifreeze could cause a valve to stick. I would change the oil again and add some rislone to make sure. Fuel injector cleaner in the tank.
If its ignition, they sell a spark tester. The next time it knocks check for spark at each plug while running with one of these pencil type testers.