Here's a quick how-to on checking your 3 emission valves. If any test fails, then the valve is faulty and should be replaced with a known good, or removed entirely, if you care to do so.

This is for a 73 only. 72 and 71 valves function a little differently. First some identification tips:

Coasting valve - small valve near secondary vacuum diaphragm assembly, above and forward of the air control valve.

Air control valve - bolted directly to the intake manifold, below and rearward of the coasting valve. Has large (1") hose coming from the air pump.

Anti-backfire valve - above and behind (near firewall) the air control valve.

CHECKING:
CV - tee into the small hose coming from the ACV into the CV with a vacuum gauge. Start engine. Gauge should read at least 16Hg at idle in N or P. Raise and hold RPMs to 2500 for 3 seconds, then quickly release. Vacuum should read no more than 1 Hg until normal idle returns.

ACV - turn ignition off and disconnect the wire that goes to the solenoid on the ACV. Connect a jumper wire from the solenoid terminal to the + of the battery. You should hear the solenoid clicking as you apply and remove voltage. Replace solenoid and/or valve if this check fails. Reconnect the solenoid wire. Attach an air pressure gauge to the hose that comes from the air pump. Remove that hoses that go to the thermal reactor and up to the air cleaner assembly. Start the engine and allow it to idle. air pressure should be .37 - .75 psi. No air should be leaking from the two other hoses you undid (all air should be going into the intake manifold). Increase RPMs to 3000. Pressure should be 1.3 - 2 psi. No air should leak from the two outlets. Hold the RPMs at 3000 and remove the solenoid wire. Pressure should drop to .75 PSi and air should flow out the outlet to the thermal reactor, but not out the outlet to the air cleaner.

An even quicker test is to hold the RPMs around 4000. Have an assistant check for hot air coming from the small tailpipe at engine speeds above 4000, but not below 4000. If hot air is coming from the small tail pipe at all engine speeds, the ACV is faulty.

ABV - run the engine at idle speed. Remove the lid to the air cleaner assembly. Find the hose that comes from the ABV up to the air cleaner. On the inside of the air cleaner place your finger completely over the opening for this hose. If suction is felt, the valve is faulty. Increase RPMs to 5000 and hold for 3 seconds while keeping your finger over the opening in the air cleaner. Release the throttle suddenly. You should feel vacuum sucking your finger for 1/4 to 1 second if the valve is working properly. Run the engine at idle speed. Disconnect the wire from the solenoid on the ABV. There should be suction at the opening in the air cleaner, and the idle should become rough, the engine may stall. Reconnect the wire to the solenoid. The idle should return to normal and no suction should be felt from the opening in the air cleaner that leads to the ABV.

I hope this quick check guide helps you get your car running. If nothing seems to work right because you cant even get the car to run, you could start with putting vacuum caps on all the valves to eliminate those as sources of vacuum leak. After you get the car running, you can reconnect one hose at a time until you find the one that causes the bad idle, and then you've found your problem.

HTH

Dave

 

WOW!!! Thanks, Dave. I will borrow a vacuum gauge and, as best as I can have the car run somehow in Neutral, I'll go through these. I do have a spare (supposedly good and/or new) coasting valve that was given to me with the car but I don't have spares for the ACV or ABV. Then again I am smog exempt so I could remove the whole setup but I need the TR hooked up for now until I find some header or something and a way to redo the ignition.

I'll be able to play with it once the car is towed to my new house. It's currently sitting near the old place

Thanks again!