After replacing the blown 302 in my truck with a fresh rebuild 300 I6, I had lots of pinging while driving at highway speeds. Pulled the codes and found the EGR system was not functional. Checked the vacuum lines, they are good. With engine running I pulled a vac on the EGR valve and the engine stumbled and stalled, so the EGR valve is good. That leaves the EGR solenoid aka EVR(EGR Vacuum Regulator)

The resistance should be 30 to 70 ohms, but the one I have was a dead short! Curious of why it shorted out I took it apart and found a diode across the coil shorted.

The spring fits in the bottom of the valve, metal disk sits on top of spring and solenoid core sits on top of the metal disk......


The diode is on the left side with the diode band pointing up. POS camera won't focos in close ups...

I replaced that diode and cleaned up the valve. Put it back together and now the EGR system is working like it should.

 

Great write up. Thanks!

Can you give is the specs on the diode that needed replacing? And where can you buy replacement diodes?

-Pete

 

I replaced that diode with a 1N4001 diode. Its a 1amp at 50V rated.

Radio Shack has them here:1N4001 Micro 1A Diodes : Diodes | RadioShack.com

I had these on hand so I used them. A 3amp- 100V rated diode would be better.

Make sure you have the polarity correctly of the diode. It is used for the kickback voltage/current stubber(so it will not spike the ECU) when the ECU undergrounds the EGR valve solenoid.

The band of the diode goes to the right side as you are looking into the connector. The right side of the EVR(notched side) goes to switched battery power and the other to the ECU. If you get it backwards, the new diode will just short out again. Or as in my case, the connector to the EVR was broken and probly the wires were crossed.

My photos are not the best for close ups and its hard to see the diode's location. Got to get a better camera.....

 

Bravo! I am impressed! 99.99999% of people savvy enough to ferret out a bad EVR in the first place, would've gone to Ebay or the junkyard, and simply replaced it.

That's good diagnostic work, and good repair work.

 

EVR from a junkyard..... well, the 3 I got were bad also! Even the one on the 302 was bad too! All had the shorted diode too. I did not even want to look up the price of a new one. nor had the $$$ for it.

By the way, the codes I was getting for KOEO was 81-85-84- 10 - 33
and KOER was 30-10-44-33

code 85 is for the missing canister solenoid(i'll stuff one in to shut the error code)
code 81 is the AIR2 inop( missing solenoid from a 92 harness that did not require it, I did put one back in the harness as you see in the 1st photo)
Code 44 is AIR2 inop (air not being supplied, non electrical issue)

Code 84 and 33 are the EGR codes I have using a 90 manual tranny ECU. I gave up using the 92 E4OD ECU as I do not have the E4OD installed(yet) and sat through a hour of codes was not fun.....

code 33 indicates the EVP sensor did not change after the EVR solenoid was commanded to open the EGR valve. If code 84 is NOT present, this indicates a vacuum problem or stuck EGR valve(mechanical issue)

Code 84 is the EVR solenoid electrical problem


So in short, when you get a KOEO code of 84, you will also get the KOER code33. But if you DONOT get a code 84, but have a KOER code 33, then probly a vacuum line is bad or stuck EGR valve.

 

Updated for the 3 digit test codes:

Code 558(84) EGR vacuum regulator solenoid/circuit failure
332(32) EGR did not open/respond


code 332(32) indicates the EVP sensor did not change after the EVR solenoid was commanded to open the EGR valve. If code 558(84) is NOT present, this indicates a vacuum problem or stuck EGR valve(mechanical issue)

Code 334(34): EVP circuit above the closed limit of 0.67 volts. This can be caused by a faulty EGR valve, EVP sensor or the EGR Valve Regulator (EVR) could allow vacuum through to the EGR when it is not supposed to.

Code 558(84) is the EVR solenoid electrical problem


So in short, when you get a KOEO code of 558(84), you will also get the KOER code 332(32). But if you DONOT get a code 558(84), but have a KOER code 332(32), then probably a vacuum line is bad or stuck EGR valve or EVR solenoid bad and not giving vaccuum to EGR valve to open