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Idlespeed system help
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....

yeah its just a case of try it and see. just make sure its all plugged in, fuses are ok, pipes are all intact, and see how it goes.

If you need anything to try, then i have a full kjet setup sat in a box (as my delorean is in bits), let me know what you need and i'll send it over to you so you can test it.
Worst thing about trial and error testing is having to buy the parts, so if you borrow them off me, you can test for free-ish (postage)
'Horsebox', where are you located?

If you're in an area near other owners, maybe a 'tech sesh' could be on the cards?
Normally all that is required is a steady flow of tea and bacon rolls for the troops Smile
Claire Wright  - Club Treasurer
Jul 1981 DeLorean - Flopsy #2292 
Aug 1989 Cavalier 1.6L - Guinney
Apr 2021 Mokka-e Launch Edition - Evie
I ran the engine and triggered the microswitch. Nothing. So I took the microswitch out, cleaned the terminals and measured about 300 Ohms with the switch actuated, so I'm guessing the switch is shot. Need to double-check before ordering a new one.

RobScott: That's an awesome offer, thank you very much. I've sent you a PM.

While I had bits off the engine, I came across this little beauty directly underneath the throttle spool cover. It's a four way connector and it's completely shagged. God knows what's holding it together. I've had a look on Ed's page but can't see what part it is. Anybody know?

Guinney: I'm in Horsham, West Sussex. I'm going to try to exhaust my own mental processes first before bothering other people too much!

It's the full throttle switch - if yours is a 5 speed, one of them will be redundant because the other is for auto kick-down.

The worst problems to solve is where someone has been buggering about previously and you have no reference for how it's meant to be. If you want to bring it all the way to Wiltshire (!), I'd be happy to take a look.
Martin Gutkowski
DeLorean Cars
Thanks for the help and PMs guys, really appreciate it. Just got the idle speed system working today!

It turned out the idle speed microswitch was broken, which I replaced some weeks back but it had no effect on operation. When I took the throttle spool cover off I found a four-way connector that was fit for the dustbin. I replaced it today, not thinking it had anything to do with the idle speed circuit, but this new connector combined with the new idle speed microswitch means the system now works.

Also discovered this afternoon, a previous owner had installed an aftermarket manually operated valve in the air supply to the idle motor. It's in 'series' with the idle motor, and I couldn't think why someone would do this rather than just fix the idle speed system. But then again there is some sense to it, as if the idle speed system fails and the factory idle motor fully opens, thats a lot of rpm to hold on the brakes (i.e. torque converter -- it's an auto), so at least this supplementary valve is a manual way in that instance of reducing the air through the engine.

Thanks again, very happy!


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