[darefugee]

Hello Folks I need help. I have a stock '89 silverado, 305 TBI engine 700R4 trans that often stalls at traffic lights when warmed up. Also will stall in parking lots when steering wheel is turned to lock. Running A/C makes it happen more often. Only bad when warm. Otherwise runs just fine gets decent mileage. 185,000 miles.

Problem came on gradually starting about a year ago. Kept happening more and more often now happens almost every traffic light unless I shift into N then maybe it still stalls about 50% of the time. It seems like when I pull up to a traffic light and stop, the engine idles lower and lower until it stumbles and finally stalls. In the last two weeks I replaced:

Plugs
Plug Wires
Dist. Cap
Rotor
Air Filter
Fuel Filter

Any advice on what to check next?

[joe_padavano]

Originally Posted by darefugee

Any advice on what to check next?

Idle Air Controller. The TBI on your truck uses a separate stepper motor to control the idle speed through an air bypass passage in the throttle body. This motor can go bad or just get crudded up and not allow the appropriate amount of air to pass for the needed idle speed. The computer in your truck monitors when the A/C is on and even monitors the pressure in the power steering (as an indication of load on the engine) and varies the idle speed appropriately to avoid stalling. Sounds like your IAC is either bad or out of adjustment.