Am I missing anything?

XJ-S
21

On an '84, the O2 sensors are not involved at idle.

22

I was thinking the centrifugal advance could be seized, but don’t they usually seize where they don’t apply any advance? In this case, can they seize outward so that they are always applying too much advance?

Another idea, the PO could have been dealing with a non-working vacuum advance, so advanced the distributor to make up for it?

I would verify vacuum advance works, like Paul says, and verify the centrifugal advance is working. If so, then loosen three screws holding distributor and retard as much as possible and see what you get. If it’s still too advanced, then you’ll have to pull distributor and go one tooth retarded, and then advance the distributor to get up to correct BTDC.

I went through this last year, it’s a bit of a pain, getting that distributor in, and having to disconnect/reconnect cap and wires several times, remembering which way is retarded and which way is advanced, exactly where it was before (take photos!). But in the end, worth it. My engine is timed perfectly and humming along. I’ll mention, my vacuum advance needed replacing, and my centrifugal advance wasn’t seized, but was sticky. I bought a rebuilt vac advance, and did a full cleaning/oiling of distributor centrifugal advance as outlined in the book. If you haven’t done these two things, you really should. Kirby states that the Lucas distributor WILL seize at some point. But after doing what he says, using synthetic oil, it has a 0% seizure rate.

23

I hadn’t thought about verifying the Vacuum advance system yet. And I have checked the centrifugal advance system per Kirby’s book and it checks out with smooth movement of the rotor.

I’ll get the vacuum system checked out and proceed from there.

24

Update:

I have run a few tests with the centrifugal advance and the vacuum advance.

The centrifugal advance moves smoothly and freely, but the vacuum advance is not functioning.

Should I rebuild the advance or would I be better off buying a new part?

25

No fun to repair. Get new britishvacuumunit.com

26

British vacuum unit, I bought an excellent rebuilt from them. Initially, I bought a new aftermarket somewhere else, piece of crap.

27

The roll pin was difficult to remove in my case (30 yrs crud), use some kinda lubricant/prenetrant and wait awhile before attempting disassemby