While idling in traffic or at a stop light, My 03 Blazer will stall out. It only happens when it's warmed up and doesn't happen all the time. To keep it running, I have to keep my foot on the brake and on the gas (to keep the RPM's from dropping). I brought it to a mechanic a year ago for this problem and a new air filter cured the problem for a while. He also replaced the fuel filter. I just checked the air filter and it's still clean. I get no codes when this happens. The truck only has 42,000 miles on it. What could possibly be causing this continous intermittent problem? I'm getting tired of driving with 2 feet because I never know when this problem will crop up! Any suggestions would be greatly appreciated.

 

Since you only have 42K on the Blazer I would check with the dealer about a warranty repair to the emissions system??? This might be a warranty item since the truck is still under 75K with the emissions system.. It sounds like a temp sensor is not reading correctly or there could be a loose wire at a connector or worst case the computer is going out...but you need to get it scanned. If Autozone or some other free scan does not indicate a problem then your only other option would be to check with the dealer you bought the truck from if you bought it new...
This is a document I found while searching my GM Service Information software, on your description of "intermittent stalling"
Document #849240:






Sensor Checks

[*]Check the heated oxygen sensor (HO2S). Check for silicon contamination from fuel or improperly used sealant. The sensor will have a white powdery coating. The sensor will result in a high but false signal voltage, or rich exhaust indication. The control module will reduce the amount of fuel delivered to the engine causing a severe driveability problem.[*]Check the engine coolant temperature (ECT) sensor using the scan tool in order to compare the engine coolant temperature with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5degrees more than or less than the ambient air temperature on a cold engine, check for a high resistance in the coolant sensor circuit or the sensor itself.[*]Check the manifold absolute pressure (MAP) sensor response and accuracy. [/ul]


Fuel System Checks

[*]Check the fuel pressure. Refer to Fuel System Diagnosis .[*]Check to determine if a rich or lean system causes the condition. Drive the vehicle at the speed of the complaint. Monitoring the fuel trim will help identify the problem.
[*]Lean--The long term fuel trim is more than 23percent. Refer to DTC P0171 or P0174 .[*]Rich--The long term fuel trim is less than 13percent. Refer DTC P0172 or P0175 . [/ul][*]Perform the fuel injector balance test. Refer to Fuel Injector Balance Test with Tech 2 .[*]Check the fuel injector driver circuit.
[ol][*]Disconnect the injector harness connector at the injectors.[*]Connect an injector test lamp between the terminals of each injector connector and note the lamp while cranking.[*]If the test lamp fails to blink at any connector, it is a faulty injector drive circuit harness, connector, or terminal.[/ol][*]Perform the fuel injector coil test. Refer to Fuel Injector Coil Test .[*]Check the evaporative emission (EVAP) control system. Refer to Evaporative Emission (EVAP) Canister Vent Valve Replacement . [/ul]


Ignition System Checks

[*]Check the ignition output using the J 26792 Spark Tester or the equivalent. Refer to Distributor Ignition (DI) System Diagnosis .[*]Check for the following conditions:
[*]Wet plugs[*]Cracks[*]Wear[*]Improper gap[*]Burned electrodes[*]Blistered insulators[*]Heavy deposits [/ul][*]Check the spark plug wires by connecting a DMM to the ends of each wire in question. If the meter reads over 3,000ohms per foot, then replace the wires. [/ul]


Additional Checks

[*]Check for vacuum leaks. Vacuum leaks can cause a higher than normal idle and low idle air control (IAC) counts.[*]Check the IAC operation. Refer to Idle Air Control (IAC) System Diagnosis .[*]Check the control module grounds for being clean, tight, and in their proper locations.[*]Check the scan tool to determine if the control module is receiving an A/C signal. Refer to HVAC Compressor Clutch Does Not Engage or HVAC Compressor Clutch Does Not Disengage in HVAC-Manual. If a problem exists with the A/C ON, check the A/C system operation.[*]Check for the exhaust gas recirculation (EGR) being ON while idling which will cause roughness, stal

 

Try cleaning the throttle body, and have the IAC checked for a weak spot near idle.

 

I had a bad miss on my 96 blazer. I finally broke down and took it to a shop after changing everything i could think of and it ended up being a bad injector wiring harness right behind the throttle body. I took the cover off it and i could wiggle the wires and make it stall out. they said the GM connectors were crappy that year.