I have a 93 S10 Blazer Tahoe with a newer 4.3 engine. It's developed a problem running when cold. It starts and idles, but then it wants to die when driven. I've already spent hundreds on tune-up and diagnostics, but the mechanic still can't figure out what's wrong.

Any tips or suggestions?


Thanks!

 

Is this a TBI motor (round air cleaner on top of the motor) or a CPI motor (throttle body pointing towards the radiator)?

Has your mechanic tried cleaning the EGR valve? A stuck open EGR valve may cause reduced performance when cold.

For either, an ECT (engine coolant temperature) sensor which is stuck reading high (hot temperature), the ECU may not command the fuel enrichment mode to maintain cold drive-ability.

 

It's a CPI.

Thanks for taking the time to respond. I'll look into the EGR. I have a feeling you may be onto something. My mechanic said he checked the ECT.

I'll let you know if we get anywhere.

 

If your mechanic has a full feature OBD1 scan tool, he may be able to see the value that the ECT sensor is feeding to the PCM.

I would have to look up the resistance values in my other references (on my home PC) to be able to tell you what it should read for a given water temperature.

 

Just an update in case anyone's following this...or encounters the same problem:

My mechanic gave up on diagnosing the problem. (Or should I say my "ex" mechanic.) He said nothing came up on his computer diagnositics.

I can't find the EGR based on Chilton's manual.

It's the worst in the morning, and doesn't run right until the engine temperature hits about 200 degrees.

Still open to any ideas...I'm at a loss.

Thanks!

 

The ECT sensor (for the computer) will be the two wire sensor. It likely is located near or in the thermostat housing. The resistance across the sensor pins will be 100,000 ohms at -40*C(-40*F) and 70 ohms at 130*C (266*F). It should be a smooth transition from cold temperature to fully warmed up temperature.

I was incorrect to label the cold start up sequence as the fuel enrichment mode. That is how the older vehicles do it. This is more of a spark advance modification for cold vs warmed up. If the sensor looks like it reads properly, then it is possible that the base timing is incorrect.