2001 Blazer 4x4 4.3L

Recently, and randomly, rpms will suddenly drop when I'm at a stop light unless I give it some throttle. It's not right when I get to a stop light, but after i've been idle for a minute or so. Happens about twice a week but it's scary. Hate being stalled - if it comes to that. Check engine light is not on, and has never been on.


It has an OK idle otherwise and revs smoothly.

I have done:
Spark plugs + Wires
Fuel pump (removed Airtex and put in a Delphi)
Oil Changes

Air filter is old, but clean.

 

Several things could cause what you're experiencing, best to start out with the simple stuff. AC Delco plugs & wires? Might want to replace the distributor cap & rotor using AC Delco as well. Put a dab of silicone dielectric grease on each terminal, inside and out, of the cap. Usually if there's crossfire going on inside the cap, the check engine light will come on, but not always. Another possibility is incorrect camshaft retard, which will also cause crossfire in the cap, and again, may or may not turn on the check engine light.

 

They were not Delco wires, but the plugs were, the wires weren't a cheap brand though. I have not done the cap & rotor yet, is it much of a chore or squeeze on our trucks?

I gave my IAC a spray with some throttle cleaner, it was pretty grimey; may or may not have helped because of the problem being so sporadic, will have to wait and see.

 

Cap & rotor are not difficult to replace, but don't waste your time and money on aftermarket parts. Use AC Delco and make sure you use silicone dielectric grease and install the wires in the correct positions in the cap.

Provided the check engine light works, the light is off, and there are no trouble codes in memory, the problem is something that the PCM does not monitor, (ignition & fuel delivery systems are not monitored).