Edmunds Answers

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  • karjunkie 03/01/10 10:16 am PST

    The first thing to do is clean all the battery connections and check the ground cable for good tight and clean connections. A low voltage problem affects all sensors and therefore the idle. If that is not it, move on to a check for vacuum leaks. Check all vacuum lines and spray starter fluid around the intake manifold with the engine idling. If you get a surge you need a new intake manifold gasket. If there are no vacuum leaks, move on to the IAC valve. Remove and clean it with throttle body cleaner and use the remainder to clean the throttle body especially around the throttle plate. Finally, the problem could be the throttle position sensor. For this you need a voltmeter connected to the TPS. Moving the accelerator pedal down should cause the voltage to go from about 0.5V to 5 Volts. If the voltage is too high before you move the pedal or there are spikes in voltage as you press the pedal, you need a new TPS. Let me know as you progress through the steps and we can take it from there. Good luck!

  • mmalone 03/01/10 1:57 pm PST

    Hi I was unable to read the voltage probing the three wires to the tps, so I removed the throtle boday assembly and did a resistance check, I was able to see a smooth transition with a resistance reading fro hi to low as I opened the throtle plates, I also checked the three wires for voltage, only the brown with white had any voltage to speek of, it read 5.03 volts, So I am assuming thats the voltace comming from the computer. Any suggestions for checking the voltage shy of exposing the wire cores?
    Mugsy

  • karjunkie 03/01/10 3:12 pm PST

    To test the TPS for signal voltage to the computer, the easiset way to do it is to insert a pin through the ground (black) wire and another pin through the signal voltage (middle) wire and connect the voltmeter probes to the pins using alligator clips. This way you don't have to damage or bare the TPS wires. Turn the key on but do not start the engine. As you manually open and close the throttle plate, watch the voltage readings at the meter. The voltage should gradually increase from 0.5-1 volt to 5 volts at WOT and back to 0.5-1 volt as you release the throttle. If you see an erratic or no movement of voltage signal, replace the TPS sensor.

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