Hello everyone,
I just purchased a 1994 Mazda B4000 with good sheet metal but she's running pretty bad. It has very bad idle and absolutely no power and Boggs with any throttle. My obd 1 code reader has thrown just about every egr code imaginable so I started replacing parts and finally got a 111 code for the koeo test which makes no sense to me because there is literally no change in its running. New parts are EGR valve, egr control solenoid and egr pressure sensor. I have found at idle the egr valve is being kept open by the solenoid, both new and old egr valve and new and old solenoid are doing this. Any suggestions would be appreciated, thanks in advance.

 

Welcome to the forum

EGR system is not used at all when engine is cold, and then, after warm up, its only used when accelerating and cruising above 40MPH

Vacuum lines should run like this
Intake manifold(vacuum reservoir)--------------------EGR solenoid--------------------------EGR Valve


The EGR solenoid should have 12v with key on but NO GROUND, so it should be closed, unplug its 2 wire connector so you can confirm its closed, no vacuum to EGR Valve at all

The computer Grounds this solenoid using a Pulsed ground(PWM) to open it(and EGR valve) a little or alot based on need, i.e. RPM and engine load

If this Ground wire shorted to ground the EGR solenoid would be open all the time, so then the EGR valve would be as well

So key on engine off, use volt meter on the 2 EGR Solenoid wires to see if it has voltage, it shouldn't
You can test the Red 12v wire separately to engine ground, should be 12volts
And the Brown/pink wire, Ground, to battery positive, should be 0v or under 3volts

If Brown wire shows Ground then move wiring harness around to see if it loses ground, so a short in the harness
This wire runs to pin 33 on the computer, and its possible the computer has an internal short to ground, you can pull it out and open it up to check