Let's see what your thoughts are on this one: When I use a timing light on my motor (stock 1.3), I notice that every few seconds the timing mark fails to appear for a split second (guessing one rev). I thought it was my timing light at first, so I bought a new one. Same result. I don't really know why, but I decided to put the timing light pick-up on the other wires just to see if I could see the timing mark from different angles and see if they skipped. What I ended up seeing is that when it missed on #1, it appeared to be firing on #4...in other words, if I put the timing light pick-up on the #4 wire, every few seconds it flashes with the timing mark at 10 btcd (where #1 should be).  Since I first saw this problem I have put in a new distributor, cap, wires, plugs, timing belt and yes I checked for a loose crank pulley...the only thing I haven't replaced is the coil. I have re-routed and separated the plug wires. It actually runs pretty good, but it still does it and it makes me crazy 
Any ideas?

Let me rap my head around this...Sounds like your bridging somewhere in the distributor.
 The rotor is pointed at #1 cylinder, but firring #4 ...?
 Make sure the small ground wire that is mounted to one of the  90 degree distributor adapter bolts has a good ground.
 ...Boxcar...

...mmm...ground wire?    I only remember the plug. I will have to look

You can actually check timing off of #1 or #4.  For every one revolution that the cam makes (which drives the distributor), the crank (which is where the timing mark is), makes 2 revolutions.  So therefore you can check the timing off the #1 or the #4 plug wire.
I have had sidekicks that had an intermittent timing miss and it was because the spark plug wires needed replaced.

Went out and checked it with the timing light after work (armed with your suggestions and knowledge) and finally figured out it was the timing light pickup not detecting the spark correctly from the plug wire. Unless I twisted fairly hard to force it into contact with the plug wire, it would have that intermitant skip. Remember, this is two  (approx $50) timing lights that did the same thing. Wonder if my spark is hot enough?
Thanks

Went out and checked it with the timing light after work (armed with your suggestions and knowledge) and finally figured out it was the timing light pickup not detecting the spark correctly from the plug wire. Unless I twisted fairly hard to force it into contact with the plug wire, it would have that intermitant skip. Remember, this is two  (approx $50) timing lights that did the same thing. Wonder if my spark is hot enough?
Thanks

So your timing light goes inline with the spark plug wire, or is it one that has the clamp that goes around the spark plug wire?  The inline ones are kinda a PITA, IMO.  I have a cheap clamp over the wire one and it works fine.
If it happens to be one from harbor freight, those are a POS.  I bought 2 of those for my bro and ended up taking both back.  They wouldn't flash bright enough to light up the timing marks.
If the spark is hot enough to make the engine run, then it should be hot enough to flash the timing light consistently.

it's the clamp type, but it's nothing like the quality of the Craftsmen one that I owned since the 1970's. Unfortunately, it disappeared 
Thanks for your help!