Idle speed issue NA 1.6

[Purfler]

Idle thoughts on a Saturday morning. Some observations on the idle issue over the last year or so:

The fixing clutch switch and oiling the dash pot both made the problem go away for a while. Not driving the car daily seems to make it come back. Sometime a long drive fixes it for a while, as does driving in traffic for half an hour or so with the a/c on. This last is from this week, it will be interesting to see how long it takes for the issue to re-appear. When it does I will again drive for 30 minutes with the a/c on.

Is there a pattern or common factor here?

Tim

[93_Clubman]

Not driving the car daily seems to make it come back.
Is there a pattern or common factor here?

28 year old car & as you say very intermittent use. Btw, Gladiator on here had a very persistent idle problem with his original NA6, which took a while to fix after trying many, many things. Think it was ultimately tracked to something intake manifold & immediate surrounds related. Just did a quick search of his posts but not seeing it - might be worth PMing him as he logged in on 04 May 21.
Doubt it's this but fuel pump wiring loom & connectors at the inside top of the fuel tank as this is where the so called black-wire issue manifests itself. Following details the issue:
viewtopic.php?f=55&t=46425
& as pics links in my original post above are US, the following shows the fuel pump loom connector, which plugs into the inside top of the tank, which is where black-wire issue occurs.
viewtopic.php?style=3&f=55&t=70835[/quote]

[Purfler]

Thanks for the reply - I wasn't really expecting any, it was just literally idle thoughts. I don't think it is fuel pump related, I recently had it out and everything looked OK. Of course that doesn't mean there isn't some sneaky bad connection somewhere!

Might just be one of life's mysteries and I'm really trying to concentrate on getting the 2000 Sports restored - which is a pretty big job. Interesting though, I've learnt more about 45 DCOE Webers, early Dunlop disc brakes and replacing points with electronic ignition than I ever thought I'd need to know.

Tim

[slomo]

This might be silly but have you checked to see if your replacement plug in the clutch pedal is still there.
If you have an a/c car, you also have the appropriate b64f ecu which will increase revs at idle when the a/c is on. This idle boost may be overcoming the idle droop from non clutch switch signal. I believe the non a/c ecu b63h differs only by the a/c idle boost.
The reason for this info is because my na8 clone has the b64f ecu but a/c delete,, and I initially overcame idle droop by turning on a/c switch.
Also the clutch switch itself could be faulty, easy check with multimeter. ( it can be dissaembled and cleaned quite easily or replaced.)

[Purfler]

Thanks slomo. You are right, the a/c increases the idle to about 1200 rpm overcoming the drop. However the idle without the a/c on is now normal - about 8-900 rpm. Could be a total coincidence. The drop will come back, it always does when the car is inactive for a few days, and I'll try driving with the a/c on again for a while.

Weird, but so are many things.

Tim

[Purfler]

So the drop came back as expected after a few days of no driving. Driving it again for about 30 minutes with the a/c on has again fixed the problem - ie there is no drop while driving without a/c on now. I expect the pattern to repeat.

FWIW.

Tim