Why does my 2001 Chevy suburban 1500 ideals down or cuts off when I stop?

Bulletin No.: 04-06-04-040 Date: June 14, 2004 TECHNICAL Subject: Idle Instability, Low or Rough Idle with Electronic Throttle Control (Clean Throttle Body) Models: 2002-2003 Cadillac Escalade, Escalade EXT 2000-2003 Chevrolet Silverado, Suburban, Tahoe 2002-2003 Chevrolet Avalanche 2000-2003 GMC Sierra, Yukon, Yukon XL with 4.8L, 5.3L or 6.0L V8 Engine (VINs V, T, Z, N, U - RPOs LR4, LM7, L59, LQ9, LQ4) and Electronic Throttle Control Condition Some owners may comment on an idle instability, low idle speed or rough idle. Cause Condition may be caused by deposits in the throttle body bore. Correction Clean throttle body bore and throttle valve plate of carbon using a shop rag and an appropriate cleaner. Refer to Engine Controls Repair Procedures - Throttle Body Cleaning Procedure. This procedure may be performed at any mileage necessary. Check to determine if the PCM calibration has been previously updated to one that includes the update for throttle body coking. For 2003 model year vehicles, look in the operating system portion of the calibration. For 2000-2002 model year vehicles, look in the engine portion of the calibration. If not, then update the PCM calibration to the latest calibration.

Cleaning the throttle body will not do the trick on the Vortec V-8. There is a design flaw. The injectors are in the intake manifold and there are poppet valves at the cylinder heads. The poppet valves stick either open or closed and cuse the engine run rough, foul plugs, etc. It will cost as much to clean the throttle body as it would to replace the injector system with an upgraded injection system. If you live in California, this cleaning and or replacement is free due to the gasoline additives. Check with GMC Customer Service.