GMC Repair: 1994 GMC driveability issue, oil smoke, cold engine

Question
Hi!
I have a 1994 GMC S-15 Jimmy 4x4, 4.3 vortec (code W) V6 with 129,000 miles.  

It ran fine until it suddenly (as in the past 2 miles) got these symptoms:
1) rough idle (as in fluctuating)
2) pungent exhaust smell (not oil smoke, but a smell I have learned is from too much timing advance)
3) dieseling when I turn it off.

I put it in my garage to look at.  After a few days, I started it, it had the rough idle and strong exhaust smell on a cold engine just like it did when it was fully warm.

None of the dummy lights are on (they come on during start up as they are supposed to).  I have yet to spend the money to get it scoped.

I have not driven it since---it is in my garage.

Thanks for your thoughts!


Answer
When was the last time you filled the gas tank ?.

At what gas level is this problem occurring.?.

If you got a load of water with your gas, you would NOT know it until the fuel got down to 1/4 to 1/8th left in the tank.

Is this a possibility ?.

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