My car refuses to start after a few stops and starts while on shopping trips - will start after an hour or so. Now about 15-30 minutes. My car has 120+ miles on engine. It may be only two stops at a store and then a start after time shopping. It may be 5 stops and restarts when it refuses to start. I heard it may be the injectors need cleaning so I ran a can of Techron Fuel Injector cleaner through. It seemed to have helped but it continued to be stubborn and would not start at times.On the about 30 miles, then at 150 miles on that tank of gas with Techron in it. I refueled with $20.00 worth and at 30 miles and again I forgot the mileage it refused to start again. When it refuses to start it chuggs and backfires under the hood. Now that I have run that cleaner through it it refuses to start for about 15-20 minutes which is better than the hour or hour and a half it was doing previously. I have been a Berryman B-12 Chemtool user in the past and I wonder if the caution I read of precious fuel system work would mean I should not use Berryman B-12 Chemtool now in my car. I would like my car to be reliable again. Hoping this will eliminate the trouble. Thank you for your assistance. Jeenee addendum...I asked this question several days ago on March 17th 2016. It just now posted on March 21st. Long delay in posting my question.