The control solenoid (the valve just to the left of the brake booster vacuum line above) was easy to test; it should be free flowing when no voltage is present and hold a vacuum on the input port when 12 volts is applied. Luckily this valve checked out perfectly as these are no longer available.
The second item to test was the EGR valve itself. In my case the original unit was still mounted to the manifold. I pulled the EGR from the car and applied a vacuum to the actuation port. The valve was "sticky" before opening. Since replacement units are still available I decided to buy a new unit: a Wells EGR118 from Autozone.
Replacement EGR valves are made to fit multiple vehicles and come with restrictors that are installed to match the exhaust re-circulation requirements of a particular vehicle. According to the chart that came with the new valve I found that I needed a size 34 restrictor. I found a bit of a problem at this point: a size 34 washer was not included in the kit! The size numbers had no correlation that I could see and the hole size did not linearly increase with the restrictor number; for example a size 7 wasn't necessarily larger or smaller than a restrictor with a bigger number. I couldn't find any information on the actual hole diameter of these restrictors online or at the manufacturer's web site. What to do?
To figure out the restrictor size required, I donned my handy calipers and measured the diameter of the plug and the opening of the old EGR valve. I then told my son, "Watch this, I'm going to solve a real-world problem with geometry!" He seemed unimpressed as I calculated the area of each and subtracted to find the area of the restrictor hole needed. By my calculations I needed a 3.5mm diameter opening in the restrictor. I then drilled an appropriate size hole in the smaller restrictor included in the kit.
For both the new EGR valve as well as the existing EGR control valve I cleaned the surfaces and scuffed them for painting.
Using the same RustOlem champagne colored metal paint (which is a close resemblance to the zinc-chromate plating used from the factory) , I sprayed a few coats on the parts and hung them to dry. As I was removing the EGR parts I also noticed that my idle screw and spring had some surface rust, so I pulled it out for paining as well. I fashioned a drying rack near a heater with a fan behind it to ensure the paint would cure.
After a few days I reinstalled the parts on the manifold. Before installing the EGR control valve, I used heat-shrink tubing to protect the wires since the insulation was cracking. I also tested the valve one more time to ensure nothing had damaged its operation during this process.
The parts are now reinstalled and a little more of my engine bay has been cleaned up. I'll test out operation when the weather warms up; hopefully soon!
