28 Apr 2014, 17:20
Hi all, would really appreciate some advice on getting the idlespeed system up and running...
A previous owner must have deliberately disabled the system for some reason because at idle throttle, the microswitch is never actuated (trigger bolt undone and doesn't contact microswitch), and the idle air motor does not buzz. At the moment the car runs perfectly well without the system but as it warms up the idle creeps upwards to settle at around 1200 rpm. So not ideal.
I've just been through the Bosch troubleshooting steps:
The ECU gets 12 V, ECU ground is good, temperature sensor is good. The microswitch test fails: measuring voltage between terminals 1 and 8 at the ECU, microswitch not activated results in open circuit as expected....microswitch activated results in about 1 V whereas we are looking for 12. I reasoned that the switch basically works, but there's a crap connection somewhere that is eating most of the voltage. An obvious culprit for dodgy connections was the white bulkhead connector next to the coil, so I cleaned the connections as best I could. I plugged everything back in and turned the ignition on. The idle air valve now buzzes (hooray!), but does so even without the microswitch being actuated.
Is it normal for the idle motor to be powered and buzzing when the accelerator is not at idle (i.e. microswitch not actuated)? It's not obvious from the circuit diagram that an un-actuated microswitch actually breaks the power to the idle air motor, and hence stop it buzzing.
I suppose the next obvious thing to do would be to run the engine and gradually close the idle screw on the fuel distributor to see if the idle valve opens up to hold the idle....
Cheers!
A previous owner must have deliberately disabled the system for some reason because at idle throttle, the microswitch is never actuated (trigger bolt undone and doesn't contact microswitch), and the idle air motor does not buzz. At the moment the car runs perfectly well without the system but as it warms up the idle creeps upwards to settle at around 1200 rpm. So not ideal.
I've just been through the Bosch troubleshooting steps:
The ECU gets 12 V, ECU ground is good, temperature sensor is good. The microswitch test fails: measuring voltage between terminals 1 and 8 at the ECU, microswitch not activated results in open circuit as expected....microswitch activated results in about 1 V whereas we are looking for 12. I reasoned that the switch basically works, but there's a crap connection somewhere that is eating most of the voltage. An obvious culprit for dodgy connections was the white bulkhead connector next to the coil, so I cleaned the connections as best I could. I plugged everything back in and turned the ignition on. The idle air valve now buzzes (hooray!), but does so even without the microswitch being actuated.
Is it normal for the idle motor to be powered and buzzing when the accelerator is not at idle (i.e. microswitch not actuated)? It's not obvious from the circuit diagram that an un-actuated microswitch actually breaks the power to the idle air motor, and hence stop it buzzing.
I suppose the next obvious thing to do would be to run the engine and gradually close the idle screw on the fuel distributor to see if the idle valve opens up to hold the idle....
Cheers!