Baffled, EGR Code 32!

I replaced both the valve and the solenoid, the brittle plastic vacuum lines with rubber ones, and cleaned the ports about a year ago. It hadn't given me a code but it ran rough and pinged under load at 1500-2000 RPMs a lot and I figured after 30 years why not. The ports were carboned up somewhat and it ran smoother afterward but it still pings under load. About a month after that I started getting an occasional 32 but only after about 5 miles at 60+ MPH. It only happens heading home from work not on the way to work and about the same spot every time, right after climbing a small hill. Another odd thing I've noticed is if it's wet out I don't get the SES light. It has become more frequent but the car still runs smooth and doesn't seem any different after the SES light turns on. Any ideas?

Just to note I had chased part of this in another thread related to the pinging: https://gmlongroof.4umer.com/t14819-1991-occ-l03-engine-pinging

I have since replaced the O2 sensor which stopped the firework exhaust smell, replaced the knock sensor, spark control module, MAP sensor, plugs, wires, cap, rotor, TPS, and Intake Air Charge sensor. All original Delco parts but my timing is still advanced 2 degrees because I have yet break the distributor hold down bolt free. More my fear of snapping it in the block. I'm currently running her on 87 octane ethanol free fuel like she should be.

The distributor bolt should not be prone to breaking. You do need the distributor bolt tool to get it loose. 2 degrees of timing should not cause any issues. The code for the EGR comes on when the computer senses closed loop, and does not get a corresponding leaning of mix from the O2 sensor when the EGR is open. You might check the port in the throttle body, and possibly the EGR port in the intake manifold for clogging. The most common time for the EGR to open is when cruising at a steady speed. If you get a code, the computer switches to open loop, and uses a standard set of parameters to run the engine. The effect of this is slightly reduced gas mileage.

P.S. Try some Freeze Off on the distributor bolt.

I just put top end cleaner through her this afternoon. When I change the oil on Friday I'll try removing the EGR and cleaning the passages. I may also lengthen the rubber hoses I used to replace the brittle plastic ones. Maybe the bend radius is too small.

Just a guess here but the EGR vacuum is tied in with the exhaust air pump control. Check that part of the vacuum system for potential leak.

Is there a way to test the diverter valve to ensure vacuum is being ported correctly?

There is no diverter valve in the EGR system. There is only a T connection to supply both with vacuum. They have separate solenoids to control the systems. The only diverter valve is for the heater control. It is hooked indirectly to the vacuum system through the HVAC system. You can usually borrow a vacuum test kit from your local Autozone. If you can not borrow one, they are relatively inexpensive to buy. Any vacuum gauge should work as long as you can hook it into the vacuum line.

I removed the EGR this weekend and cleaned some carbon buildup. I checked the hoses for damaged and misrouting, nothing visible. I haven't had a chance to get a vacuum gauge on it. I've had a rattle for a long time from the transmission in reverse which has seemed more prevalent lately and has recently gained a slight hesitation in and out of OD, so I put some shudder fix in it yesterday. Today on the way to work, could be just a coincidence, but the SES did come on but I noticed the pinging stopped when I accelerated. The transmission was also quieter after the 18 mile drive to work. Don't know if the pinging is actually related to the transmission rattle but the 32 code SES light has never stopped the pinging before. Unfortunately, I do not have a paper clip available here at work to check what code it set but 32 is the only one it's ever set in the four years I've owned the car. I'll get a better idea on the way home once the SES resets and I pull the code.

I put the old EGR Solenoid back on a couple months ago and the 32 code never came back. Apparently it was initially the valve but because I also replaced the solenoid I wouldn't have known that because the new Delco replacement solenoid was bad. Who'd of thought a brand new solenoid would be bad out of the box.

Happens a lot more than you would think.