2001 Chevy Silverado 1500, 6cyl. Appx 290,000 miles

Early this week I drove from Dallas to San Antonio, then to Houston. While in Houston, I had to park on the top floor of a parking garage (9th floor). When leaving the garage (while still on top floor) - my engine started stumbling, and the Check Engine Light (CEL) came on - FLASHING.

I made it out of the parking garage, and within 100 yards of the building, once leveled out - the light went off, and the engine again ran smoothly.

So - here's what I know:
Almost 0' elevation - suddenly to 9 stories tall elevation.
Parked on a downhill grade/incline (appx. 2 hours parked)
Driving out of the garage - engine stumbled the whole way down, with CEL still flashing
Once level, CEL off and engine runs smooth
Oil was changed last week. Oil level was full when I had a chance to stop and check it on my way back to Dallas that day.

Any ideas what may have happened to cause the stumble and CEL? Computer adjusting to sudden atmospheric pressure change? Oil level covering an oraface when on downhill grade (or away from oil pump inlet?)? What else could it be?

I'll take the truck to AutoZone today to see if there is a stored code in the computer.

Thanks,
Rex S.

 

Fast followup... No codes stored in the computer.

 

Well, there's a thing for elevation change. It's called a MAP sensor, and your truck has one. 9 stories shouldn't hurt it all that much. I'm guessing it's either a fuel related issue (contaminated perhaps) or because your truck has a 4.3L engine that uses popped style injector valves, your fuel pump sucked in an air pocket on the deep decent and caused the poppets to act erratically.