Alfa Romeo Bulletin Board & Forums - View Single Post - Weber Idle Adjustment Problem
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post #21 of (permalink) Old 12-08-2018, 02:28 PM
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Join Date: Dec 2017
Posts: 37
Hey folks, need some additional advice here. It seems I got ignition sorted, yet still having problems with cyl #4. When fully closing the idle mixture screw for that barrel, I get no change in RPM (basically the same original issue). Checked spark plug, swapped spark plugs, checked lead from dizzy and everything seems to be flowers and spring from an electrical standpoint.

Had the weber off again to check out the cold start circuit. Someone apparently had caused trauma to one of the cold start pistons and it was stuck partially up. Remedied that and ended up just blanking off the whole system with a kit to try to stay sane.

No real change. I've made sure fuel can successfully feed in through both the progression holes and the idle mixture hole, and after running, both areas do have fuel in them. Idle jets are cleaned out and have been swapped before to no effect. Butterflies at idle are just uncovering part of the first progression hole. I can't find anything that could be keeping fuel out of the cylinder or leaking it in from elsewhere, nor can i find any reason for ignition not to occur.

Odd symptoms:
1. When covering other carb barrels to starve that cylinder of air, the engine loses RPMs precipitously as expected. When covering barrel #4, it starts gaining RPM very quickly.
2. Spark plugs for other cylinders were someone white-ish after idling for several minutes. The plug for that cylinder was light brown and uneventful.
3. Barrel #4 still pulls at about 80% vacuum compared to the other 3 (slightly low). Checked mounts, checked brake booster attachment, but everything seem to be in order.

I feel like symptom #1 is the key somehow. Do I potentially have a cam problem? What other things can I be checking here? Thanks.
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