Lucas vacuum advance as low as 300 RPM
Rgds
David

PS: previous post ..the 123 "500" RPM for no advance may be Distributor RPM, which would be 1000 RPM at crank?? meaning all your idle numbers of 750-350-900 would be at static advance only??

 

I have a series 3 so there are several big differences but I've struggled with the idle drop as well. I've tried many of the things mentioned above that appropriate for the series 3 including a petronix system which did help somewhat. The other thing was adding some resistance to the Coolant Temperature sensor since it was not calibrated correctly.

My mechanic thought it might have been a compression issue, but that turned out to be good.

I just talked to him about it last week and he says "the engine is fine, it might be the torque converter"? A transmission issue?

It is like the resistance of putting it in gear seems especially high relative to other cars. Does this make any sense to anyone. Could that be the issue?

1986 Xj6 Series 3

 

I think your mechanic could be right, I've been thinking along those lines too. Since last posting on the subject I discovered my 123 Tune + distributor was barely receiving any voltage. I ought to have noticed this before as amps and volts are shown on the app. I connected a direct live feed to the 123 and voltage went up to around 13.5. This led to a bit of research and it seems the 123 sometimes doesn't work too well with a ballast resistor so I fitted a non ballast coil and by-passed the resistor. This made a significant improvement to how the engine runs and a slight improvement to the drop in RPM. But.......the revs are still dropping too much so back to my opening line regarding your mechanics thoughts.
Bearing in mind the improvement I decided to postpone any more tinkering as I was able to enjoy the car over the latter part of summer bar the occasional stalling episode. It starts well and runs well however it still isn't right so I'd be interested to see how you get on !

 

As long as I park the car and start with no AC, I'm good to go so far. I'm just in search of the perfect idle, which might be impossible. One thing I never checked was the spark plug gaps, so I'll look at that this weekend too. Otherwise, I'll probably wait a bit and maybe find out some day if I need to service the transmission.