my car seems to run pretty decent, other than once i have been stopped in gear for a few seconds, the rpms will drop and fluctuate from 6-900 and occasionally die. doesnt always do this, but usually. never died while driving or anything. and when i check the timing, est connected or not, the mark jumps a bit, always returns to the tab, but reduces the timing maybe 5 degrees for a split second, maybe every 2 seconds. any thoughts? balancer off maybe?

 

Last time I had a problem with the timing mark jumping I found the timing chain to be rather loose. There is a simple way to check it.
Remove the distributor cap, turn the engine over until you have your timing mark on the balancer lined up with the timing tab marks. You will probably need a buddy from here on. The idea is to install a wrench/breaker bar on the balancer bolt to turn the engine back and forth and have someone watch the rotor button on the distributor, at what point the rotor button is stationary before it moves in the other direction is the amount of slack in the timing chain, you count the degrees on the balancer. Factory GM manuals give you a spec to be within, I can't remember what the number is exactly but I would say no more than 2-3 degrees would be ok. This procedure would tell you whether or not the timing chain is on the way out, maybe too loose etc... always good to check anyway, and atleast you can eliminate this possibililty with a few minutes of your time. Just a suggestion, hope this helps, Larry.