idling problems on 1994 Toyota Pickup

after the truck gets to a normal operating temperature, the idle surges from 800 rpm to 2500 rpm usuallywhen the breaks are applied. i have been looking for a vaccum leak but havent had any luck. can someone lead me on the right path?

by in Williamsport, IN on November 13, 2009
2 answers 1 comment
ANSWER by on November 13, 2009
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.
COMMENT by on November 13, 2009
Vehicle Application: 1992 Toyota Pickup 2.4L, Vin R, Eng Cfg L4, Eng Des 22RE Customer Concern: High surging idle up to 2000 RPM when hot. Tests/Procedures: 1. Make sure there is good hot coolant to the auxiliary air control valve and make sure the thermostat is working. 2. Remove the air boot and block the hole in front of the throttle plate that supplies air to the auxiliary air control valve (wipe that area of the throttle body clean and use dum dum or duct tape) and then put the air boot back ON and start the engine and see if the engine RPM is still high. If the RPM comes way down, then the auxiliary air control valve is staying open. Replace the auxiliary air control valve as necessary. Potential Causes: Sticking Auxiliary Air Control (AAC) Valve Tech Tips: If the Engine Control Module (ECM) sees high RPM and closed throttle when warmed up a little bit, the ECM goes into deceleration fuel cut and cycles the fuel injectors off causing the surge. There is an auxiliary air control valve located below the throttle body that is a wax pellet style valve that should open when cold to allow air to bypass the throttle plate for fast idle cold. Engine coolant should heat the wax pellet as the engine is running causing the wax pellet to expand and block the air passage to lower the RPM as the engine warms up. The auxiliary air control valve should be closed when hot and is not designed to keep adding air hot.
ANSWER by on June 10, 2014
When my 1994 dlx was doing that, it turned out to be the max air flow meter.
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