Vehicle: 1988 - 1994 Toyota Pickup 2.4L
1988 - 1994 Toyota Pickup 3.0L
Symptom: Idle surge with the brake applied. The vehicle is actually in fuel cut mode.
System: Emissions/PCM/Fuel
Codes: N/A
Problem: The idle speed is too high, and the engine control module (ECM) goes into fuel cut mode.
Test & Fix: The first step is to make sure the auxiliary air valve is closed when the engine is hot. Remove the inlet air duct at the throttle body so the throttle plate is visible. In front of the throttle plate, on the lower left side, is an air bypass hole. Plug this hole with a piece of tape and reinstall the air duct. Start the engine and see if the idle rpm is normal and that the surge problem has gone away. If so, the auxiliary air valve is stuck slightly open. To test the auxiliary air valve, first verify the cooling system is full of coolant and that there is no air in the cooling system. Also verify the coolant hoses are good and hot to the auxiliary air valve and that the valve is clean. If there is good hot coolant flow through the auxiliary air valve and the valve is clean but the valve is staying open, it will need to be replaced. Also check the idle air bypass screw setting for correct adjustment. The adjustment setting should be one to two turns out from full bottom but use the appropriate service manual to properly set the air bypass screw. If someone has used the air bypass screw to turn up the idle speed, the idle can be too high and also cause the engine to surge.
