Quote:
Originally Posted by jdc1244
Are you having a problem with high idle or rough idle? I assume both can be present at the same time but often it’s one or the other. Unfortunately I’ve had experience with both.
You seem to be referring to a high idle so I’ll address that.
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Yes, the idling was both high and rough. On no load the car would idle at about 1200rpm. And with a miss every few seconds at most.
But I fixed it! Turns out the throttle switch - which I hadn't even known existed until I saw a photo in another thread - was not closing when the butterfly was completely shut. I expect that the coupling slot is just worn, because I whacked it, hoping to realign it slightly, and it started functioning again! Finally the engine was aware of a no-throttle situation, and the ICV and idle jet (which I'd previously cleaned and checked) started to operate, and the idle dropped to 600rpm.
But the roughness and missing was still very much present, and in the course of fiddling with the distributor I noticed faint signs of arcing around the cyl 2 contact inside the distributor cap. Checking showed that the #2 spark plug cap was open circuit, so I jerry-rigged a replacement. Perfect, smooth, clean 600rpm idle, and oodles of power!
Everything is massively better, but I still have this weird situation with the idle mixture control. I'm very grateful for the information you supply:
Quote:
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Yes, the idle adjustment screw does contact the sensor plate lever but it does not have any contact with the fuel distributor; the FD is effected by the position of the lever which indicates the amount of air entering the engine. The adjustment screw is more for ‘fine tuning’ than addressing a major high idle problem - which would explain why your adjustments of the screw have not solved the high idle.
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As far as I can see, even with the engine off, the idle screw is a long way from contacting the plate lever. This is why I was wondering if the screw did its work some other way, and it's really useful to be put back on the right track.
I suspect the screw itself may be busted off somehow, and I'll cross-check it against the 420SE I have here and see if I can make sense of it all.
All things considered, though, I'm really happy to have this engine delivering the right stuff at the right revs. I think it's a useful lesson for others with rough idling and/or running:
don't forget to check the HT cables and caps! Those kilovolts will try very hard not to go where they should, and if they get loose they'll burn things! New HT leads all round after a few 100kmiles could pay for themselves in fuel very quickly.
Many thanks for the invaluable info.
CD