Won't Start

Hi,
I am new. I have a 1992 Jimmy V6 4.3L vortec engine. I have been having some trouble with my Jimmy. The trouble is sometimes it won't start. The last time it hasn't started is last Thrusday night. I towed it to some local shop. They didnot say much, but when they try to start it on Friday it worked. I have been driving since than. So far it has been working fine.
Thanks

Pull the upper plenum and look for signs of washing (where one side is cleaner than the other) If the passenger side is washed, it's your CPI unit, if your driver's side is washed, you have a bad nut kit...Replace the nutkit anyway if you replace the CPI so you don'thave to pull it later... Some will tell you to pull the throttel vane and look down into the plenum, but that's not often accurate for the signs of washing...Do it right and pull the plenum.

thanks rlith i will look at that tomorrow.
:)