All EGR seems to be working propery but still code 34

[mdula]

So, I got a scanner, used it on my 86 GT, a few codes popped up (KOER) all for air thermactor flow and 32-EGR insufficient flow. Concentrating on EGR code 34. This is what I can tell, after each changes made below I reran the KEOR scan but still get a 34. Engine runs fine, but I heard an improper functioning EGR can cause MPG issues and cause it to run rich.


1. Swapped EGR valves, had an extra one in garage in really good shape. Also cleaned the original one and tried it again.
2. Operated EGR valve with vacuum pump while engine running to 5 lbs and engine stuttered and died instantly so I know the valves are not blocked and diaphram works. Also held 5 lbs and didnt bleed off.
3. Checked all vacuum lines and found a bad route / blugged port that feeds vacuum to the passenger solenoids. Fixed that, same codes.
4. Checked 12v at the egr regulator solenoid, when plugged in 12v to both wires.
5. decided the solenoid wasnt working, replaced it with a new one.
5. Using a wire diagram found the wire lead that operated the solenoid, grounded it while engine running, it sent vac to the EGR valve and the engine died.
6. Check and cleaned ECU ground wire.

So, the EGR system functions properly from the solenoid acitvating, sending vac to valve and the valve operates as it should. My next thought was the ECU isn't sending the signal, but the wires are all in good shape. What am I missing? The code 34 from the book, means "lack of EGR air flow" not EGR error, or not opening at all.

Any help appreciated! Thanks all,

[JACook]

OK so, first, an '86 does not have any way to sense EGR flow. On an '86, the KOER 34 code is about the
EGR valve position sensor not tracking where the ECU is telling the EGR valve to go.

This could be a sensor problem, or the EGR solenoid is not following commands like it should. The EGR
solenoid works by alternately providing vaccum, and venting vacuum over and over at a fast rate. So a
slow EGR solenoid would not show itself by just powering the valve and watching it kill the engine.

[mdula]

OK so, first, an '86 does not have any way to sense EGR flow. On an '86, the KOER 34 code is about the
EGR valve position sensor not tracking where the ECU is telling the EGR valve to go.

This could be a sensor problem, or the EGR solenoid is not following commands like it should. The EGR
solenoid works by alternately providing vaccum, and venting vacuum over and over at a fast rate. So a
slow EGR solenoid would not show itself by just powering the valve and watching it kill the engine.

So, the regulator solenoid was replaced and the other EGR valve I had laying around that I put on also had the sensor on it so it was swapped. 2 EGR sensors and 2 regulator solenoids both cause the same code. Could it be both EGR valves/sensors are just bad?

But what your saying is code 34 doesnt really mean the EGR flow is not flowing but that the sensor on the valve is telling the computer its not open or closed where it shoud be? If Im not mistaken, can I not test that sensor with an ohm test, and putting 5lbs of vacuum on the sensor? Just wondering what to do next. Thanks for the reply JAcook