[RESOLVED] idle switch help

[need2boostpsi]

Alright so i have noticed a slight surging at idle, when im driving and on deceleration(foot off the pedal) the car doesnt cut fuel, my logger still states the IDC is 1.5% and the exhaust will kinda bubble and pop. so my hunt starts, first thing i did was check the idle switch with a multimeter, it was working fine. then i checked the green wire at the ECU pin 14 on a 1991+ i believe, still showed the switch working. The last place i checked was with the key on the voltage coming from the ECU to the switch, and nothing (i believe it should be close to battery voltage, with a low current).

So i swapped ECU's i had an extra ECU that wouldn't start the car, but my logger could read the sensors, checked the voltage at the wire and it was about 10-12volts.

So my questions are; 1) is there suppose to be a voltage at the wire from the ECU, 2) would this cause my problems, 3) if im just nuts and there isnt suppose to be a voltage, how do i test to make sure the ECU is seeing input from the switch?

Thanks,

Will

 

[need2boostpsi]

anyone have a clue?

 

[need2boostpsi]

I just need someone with a multimeter to check the voltage at the IPS wire for 12v and ignition on.

 

[need2boostpsi]

maybe Steve could chime in?

 

[cbrfrenzie]

I believe with the throttle closed, switch engaged, that line should be grounded. With the throttle open, switch disengaged, that should be an open circuit. The ECU would detect the input by the current flow through that ground connection.

 

[need2boostpsi]

im talking about the car key in on position and wire off the switch. I think there should be some voltage from the ecu?

 

[need2boostpsi]

alright i have resolved this, my ECU was rebuilt before i bought the car, well they rebuilt it with a 1990 core i checked the numbers on the white connector and they match up to a 1990 ECU

 

[steve]

To answer the original question, yes, I'm sure that the ECU pulls up the IPS signal to 12v. The diagrams show pull ups at the MAF end for the reset line but I think there is a weak pull up on the board too.