Need help troubleshooting vacuum system

[Håkon Mathias Bergvik Trulsen]

I just bought a 1986 Toyota AE82 Corolla, with the 1.3l 2E-E52C carbureted engine.
It starts up on the first crank, idles smoothly around 900rpm for 1 or 2 seconds, and then it stalls. It also dies instantly if the throttle is applied, but if the throttle is continually pumped just the right way, the engine revs up while sputtering, with an occasional backfire through the carb.

The previous owner said the car gradually ran worse, but was still driveable, until it sat unused for a couple months this summer. When he got back to start it again the problem was the same as now.

I believe the problem lies in the vacuum system, as there is an audible abrupt hissing sound, as if a vacuum valve was opened just before the engine dies when the throttle is pressed. I replaced a vacuum valve I found to be leaking, and the engine was slightly easier to keep revving afterwards.

I have checked all the vacuum lines, and I didn’t find any obviously leaking lines or fittings. All the actuators and valves seem to be functioning after replacing a faulty one, as I have tested them by sucking on the lines and they hold vacuum.

I have a hunch that the original problem was the valve I replaced, and someone “fixed” it until it was worse by screwing with the vacuum hose routing, as a couple of lines lead to the air cleaner.

I can’t find a vacuum diagram that matches my car. I have a sliding piston type carb, not unlike the pierburgs found on old Volvo’s, while all I find on Google is a standard downdraft style. The carb has no markings except for the Toyota logo.

Any advice and tips for how to proceed with the troubleshooting or where to find the right vacuum system diagram will be greatly appreciated!

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Topic

[Richard Kirshy]

Might see if any of these offer clues..
https://www.google.com/search?q=1986+Toyota+AE82+Corolla+vacuum+diagram&client=firefox-b-1&tbm=isch&source=iu&ictx=1&fir=a0sZdlD-JNgHGM%253A%252C8nH9OmoFzZGp3M%252C_&usg=AI4_-kSzp4vVqbZMtHsygoxYR1ubjsjGQQ&sa=X&ved=2ahUKEwjE2oH31fTdAhUlVd8KHQv4Bw0Q9QEwAHoECAUQBA#imgrc=g5melQhHsCikYM:
Also you could smoke the system to see if there are any leaks.
Beyond that you also may want to look at the carburetor, it’s looking like it could do with a rebuild.

[Håkon Mathias Bergvik Trulsen]

I’ve searched google quite thoroughly allready, and I couldn’t find the right diagram. This is what seems to be the closest based on the shape of the carb and the vacuum components, but I cant find the thing circled in green, and the thing in red only has two ports.

How does one smoke the system? Does one need special equipment? I might be able to get my hands on a smoke machine for stage use if that could be used.

The carb is a bit dirty on the outside, but the float bowl and the jet is squeaky clean, and the piston (or variable venturi as I discovered it’s proper name is) moves freely, and reacts well to change in throttle poisition and RPM the few seconds I can get the car to run. I doubt it is the problem, but I’ll try to find a rebuild kit.

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[Richard Kirshy]

[Håkon Mathias Bergvik Trulsen]

Thanks, those videos were quite informative. I’ll try the smoke test tomorrow

[Håkon Mathias Bergvik Trulsen]

So I did the smoke test yesterday, couldn’t find any leaks.
I did however find out the fuel cutoff valve in the carb didn’t get any power. I should have checked that it got power as one of the first things, I checked the valve itself, but I didn’t think of it.
Anyways, the engine starts now, and it seems to run normally once it gets going, however it’s really hard to start now, I have to crank it for almost half a minute before it barely catches and reeeeealy slowly climbs to normal idle speed. I still think the vacuum system routing is off somehow.
At least the car is driveable now once it gets going.

[Richard Kirshy]

You might try a Toyota dealership and see if they can get you a diagram of your engines vacuum system routing.

[Håkon Mathias Bergvik Trulsen]

Yeah, I allready called yesterday, they said they would call me back once the guy in charge of the service and repair department is available.
Thanks for all the great tips!

[Mathieu]

You have a unbalance air to gas mixture and might be a timing belt position problem. A loose rubber trimming belt can stop a car from starting and can to rough iddle.
It’s simple to look the timing belt position.
Start at 11:45 minutes

If you really think is a vacuum leak, you might do again the smoke test in a different way.

[Håkon Mathias Bergvik Trulsen]

I adjusted the timing properly, disconnected the vacuum advance, and using a timing light to set it.

It was only off by about 1°, but after setting it to exactly 5° (as the Haynes manual recomends) the car is much easier to start. It still requires the throttle to be fully depressed, but now it catches and starts in about 5 seconds as opposed to 15-20 seconds before. It also got a noticeable boost in torque.

I didn’t expect the difference to be that noticeable, I’m used to tuning the ignition by ear and butt-dynoing/doing timed pulls in my Opel Kadett C, it requires far greater adjustments to be noticeable. I think it shows how far ignition control systems and engines in general evolved just in the one decade between the cars (the Opel is from 1979).
As to plasmide56’s suggestiin, checking the cam timing has been done, the timing belt hasn’t skipped.
And to clarify, I’m quite sure there isn’t a direct leak in the vacuum system, but rather that the routing is wrong. Some switched vacuum circuits lead to atmospheric pressure, so if the right valve opens at the wrong time, it would cause an intermittent vacuum leak.

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