EGR Valve hose connections for 1978 Toyota Corolla 5 speed wagon.

[MyCorolla]

I had not been using my Toyota for a few years but it still starts up.

I went to see if it would pass smog but it fails at idle speed. When cold, the car runs fine, but I noticed that when the car warms up the idle starts to race back and forth. I tried smoothing out the idle by adjusting the two carburetor screws but no matter what I do, when the car is cold it runs fine, when it warms up, it starts to heave and race on the idle.

I have replaced the fuel filter, the air filter, some vacuum hoses, and I cleaned out a very carbon filled EGR Valve. I spent 3 or 4 four hours cleaning the EGR valve and where it connects to the engine block.

Any suggestions, and does anyone have a picture of the EGR hose connections in case I put them back incorrectly?

After I put everything back together, the car definitely runs better, but the core problem that I want to fix, the inconsistent idle after warming up is still there, not as bad as before, but its still there.

Can I reconnect hoses and bypass the EGR system entirely (as a test) to see if that is still the problem?

[rickhart]

Close off the EGR entirely by capping any hose that leads to it or the actuator. The damned thing has always been nearly useless in reducing NOx, and it makes for a bumping rough ride by rapidly cycling ON and OFF, most noticeable at about 40-45 mph. If it doesn't stay closed at idle , it will cause that surging problem you describe. Also, old crappy gas that can't burn correctly will show up more when the choke turns OFF.

Can't really tell if this will solve your problem, but it is a good place to start.

[MyCorolla]

There are two vacuum plugs with two blue plastic connectors for hoses that are part of the vacuum and the carburetor.

I accidentally broke both off of plugs. Where I can buy the plugs and what are they called? The are near the carburetor on the top of the engine but below the carburetor.

I should add that when I sprayed WD 40 near the base of the carburetor, the part closer to the windshield, the idle settled down. So I probably have a vacuum leak somewhere.

I am also wondering if the Idle control valve voltage line is working correctly.