S10 pick-up has a jar and dies at lights? on 1990 Chevrolet S10

My 1990 Chevrolet S10 pick-up has a very light but noticible jar when it is idling and sitting still. It does not do this when it is driving; it seems to only do it when the brake is applied. It also dies when sitting at a red light for to long. It always starts right back up but it has become quite the inconvenience. Can anyone help? All help will be greatly appreciated.

Asked by for the 1990 Chevrolet S10
Many models need to have their throttle body cleaned because they get 'coked' with oil residue. The oil residue on the throttle valve (butterfly) and throttle bore closes the throttle opening so you get a low idle condition and stalling on deceleration (when stopping). You can spray a shop towel with throttle body cleaner and clean the throttle valve and throttle bore. I would also look for any vacuum leaks because the hoses can become dry and cracked over time. A failing idle air control valve may also be causing this but that will require some diagnosis. We don't want you waste money on parts you don't need. Which engine is in the truck? Fuel injected?
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the heat mod under the rotor bug is fried.