I have a 4.3L TBI injected 1991 Jimmy and I want to deactivate the EGR system. However, when I disconnect the EGR and plug the line the ECM somehow figures it out and throws a code (always on the highway).

How does the ECM know that the EGR has been deactivated? I leave the EGR solenoid and lines hooked up and fuctional but I disconnect the valve itself and plug the line.

Somehow it's figuring it out by looking at other engine parameters but what parameters? Is there a low-buck way of deactivating the EGR without burning a custom chip? The whole truck isn't worth as much as a custom chip.

 

The ECM monitors MAP and O2 sensor readings to see if the EGR is opening up.

The only real way to disable it is to make a custom chip with all the EGR functions turned off.

 

Read the "Lowdown on Code 32" in the Tech Articles.

 

That's what I figured. Unless there's something physically wrong with my EGR valve I gotta say that the stock programming is junk. The motor clearly wants either less EGR duty cycle while accelerating or more ignition advance when the EGR valve opens. My brother with an identical engine in his 91 Blazer reports that what I am experiencing is "normal" for that engine. i.e. his does exactly the same thing. Some programmer at GM musta had a bad hangover when he programmed this engine calibration.

I have gone onto several chip burning websites and they all make claims of BIG improvements in torque for this motor as well as a few HP. Far above the claims they make for most of the V8 TPI performance engines. I can beleive it, given how sluggish this motor is with stock programming.

This might be the motor I cut my teeth on burning my own chips. I am sure I could do much better than the factory did. HP I could care less about. What I need is serious low end torque for towing my boat.