1986 Toyota Pickup Stall at Idle

Hi Phoebe3,

Thank you for the donation.

Is this a carburetted or fuel injected model?

Is the performance of the engine poor now?

Have you checked if any of the spark plug wires are dislodged?

Hi,
The truck has a 2 bbl carb. The spark plugs are good and connected. The engine won't idle below 1200. It just dies when I let off the gas and the RPM drops below 1000. It runs rough even at 1500-2000. I think there is a vacuum leak. I hooked up a vacuum meter and when the RPM falls below 1000 the vacuum drops to zero fast. I can make it run smooth by holding my hand over the carb to block almost all the air and then the vacuum goes to 18. I have disconnected all the vacuum lines I can find (with good notes) and plugged the holes and it still won't idle. I think I am looking for a large hole because I really almost completely block the carb to get it to run smooth at idle.
This truck has California emission control equipment.

You should be correct about vacumn leakages and it is one of my most dreaded situations, even more so without the presence of the physical vehicle. One of the way to test for vacumn leakages is with the aid of carb cleaners. With engine running, spraying carb cleaner onto suspected leaking areas would result in the engine speed changing. Let us start with possible areas that can be checked first before getting on with the carb cleaner. Possible areas : 1. PCV valve. 2. Intake manifold gasket. 3. Vacumn hoses. 4. Vacumn valves/solenoids. 5. Carburettor gasket. 6. EACV 7. Air suction system. If test and visual of the above components are non conclusive, then is time to get the carb cleaner. Below is a description and testing procedures of the air suction system. 1. Check condition of all hoses and tubes. Ensure coolant temperature is below 43 °F (6 °C). Start engine and ensure a bubbling noise is not heard from Electronic Air Control Valve (EACV). 2. Warm engine until coolant temperature is between 64-109 °F (18-43 °C). Maintain engine speed at 1390 RPM and check that a bubbling noise is heard from EACV. 3. Continue to run engine until coolant temperature is above 131 °F (55 °C). Maintain engine speed at 1390 RPM and check that a bubbling noise is intermittently heard from EACV. 4. Allow engine to return to idle and check that a bubbling noise is heard from EACV. With coolant temperature above 64 °F (18 °C) and engine under heavy load, disconnect vacuum hose from vacuum switch and plug end of hose. Ensure a bubbling noise is not heard from EACV.