91 toyota Pickup truck 2.4L with idle problem

engines
brakes

#1

1991 toyota pickup truck, 4wheel drive, manual 5 speed, 2.4L 4 cylinder. Hello, my pick up truck idles too fast (after warming up, dosen’t do it when cold) and when I step on the brakes the engine surges. I tryed to adjust the idle jet on top of the throtle body and even with it screwed all the way down, makes little difference. Also tryed disconnecting the vacume line to the power brake booster no help. Someone said It could be it’s low on coolent but I check that and it is cmpletly full. Anybody got any other ideas?

Stuck Paul


#2

i have the exact same issue, i just read tha the problem occurs in the engine control modual or ECM, i’d try looking in to that before wasting to much money like i did. and if that isn’t it pulling your fuse for your gauges may stop the surging you loose everything but your speedometer. Hope that info helps


#3

When the engine is cold, it needs more air and more fuel. In old carbed vehicles this was the function of the choke and high-idle circuts. In your fuel injected truck, there is a temperature sensor in the coolant stream and an idle control stepper motor. When the engine senses it’s cold, it opens that stepper motor up more and tells the fuel injectors to deliver more fuel.

So either the temp sensor is faulty, your thermostat is faulty (the coolant stays cool, even though the intake manifold is warmed up), or the idle control motor is faulty or gummed up. The thermostat is easy to check-- is the temp gauge going up or is the top radiator hose hot? If not, that is likely the issue. If you have a good service manual, it may give the ohm range the sensor should be producing at certain temperature ranges and you can test it with an electrical multi-meter. The IC motor can be taken out and cleaned and lubricated.