Am I missing anything?

Over the past two weeks I have done a few tests for the engine in my 84 Lucas. All the coolant, air, and throttle position sensors are at the correct spec. The lines to the Map sensor seem to be in good condition. The plugs and wires are new with a good blue spark from the coil. The injectors have been cleaned and new fuel lines with good fuel are installed. I have checked the mechanical advance as per Kirby’s book and all is well.

However, I find that I am still having major problems somewhere in the system. Backfiring and a reluctance to rev at cold temperatures still plagues the car. My last guess would be the o2 sensors. Is there something I have forgotten to check?

Presumably you mean cold coolant temperature?

How long does this misbehavior last? Until the engine is thoroughly warm? Only for a minute or to after a cold start?

The fuel injection system will be in ‘open loop’ (not using oxygen sensor readings) on a stone-cold engine…but will begin using their input before the engine is thoroughly warmed up.


When is the last time you took the car out and really gave her the boot? The “Italian Tune Up”? When mine gets a little cranky when cold, it’s my reminder blow out the cobwebs.



Its usually about 5-10 minutes of opening and closing the throttle to warm her up

Its been just about 17 days or so. I don’t get to take her out much (no plates until I pass inspection)

Another thread you were checking ignition timing, I think? Is that set correctly?

I got the plugs and firing order sorted and I seem to remember the timing was good but I don’t have any numbers to prove it.

I think I’ll use my friends timing light again for some actual numbers.

The timing specs for your car are located on a decal under the hood. Timing is typically checked at 3,000 RPMs and with the hose to the distributor vacuum advance removed and plugged. But, check what your decal says and use that.


For US-spec Lucas HE V12s, it’s 18 BTDC at 3000rpm, with vac advance disconnected as Paul states.

For a quick check by yourself (because the above needs two people), disconnect vac advance and plug, check at idle. If properly timed at 3000RPM, then at about 800RPM it should be 4-0 BTDC.

Okay I will check the timing tonight and report back.
Thanks for the info!

I don’t think that blipping the throttle on an EFI engine enhances the running… On old USA carb cars, yes. Acceleration pump adds fuel.

I apologize for my tardiness but the test is complete

The car is (depending on the distributer adjustment) 18-35 degrees advanced

And I believe the o2 sensors are not working
Brought the engine to temp. And unplugged the o2 sensors with no change to engine behavior.

My question here is:
How could the engine advance so much at idle,
And what do I do about it?

Did you disconnect the vacuum advance hose to the distributor and plug it?


Yes it was disconnected during the test

What is the history of this car? Did it work properly for you at one time and then just start acting up all of a sudden? Or did you get this car with it running poorly?
The reason I ask is that it is possible that someone before you took the distributor out and then installed it improperly. Do you think that might be the case? It is easy enough to do.


I bought the car in August from a seller who claimed it wasn’t running. When I got there my friend and I got it running very quickly and listened to it for 5 or so minutes while it warmed up. I then paid for it, got the title, drove it across the city, and began work. Apart from that, and what I have found in service records in 1990’s, I don’t know anything else

The distributor has been open before. The advance mechanism has been overhauled, the cap, and rotor are also new. I was worried that the PO had messed with something.

When in P or N, it is in open loop, O2 sensors are only used when in gear.

18-35 degrees advanced at what rpm???

Since the distributor was worked on before, it was removed from the car. The gear at the base of the distributor has 14 teeth so each tooth is 25.7 degrees. So if the distributor was reinstalled one tooth off that could explain the timing readings that you got.
It is a bit tricky to get the distributor installation alignment correct and the engine will probably run poorly if it is one tooth off, but it might run.
I suspect that the prior owner or their shop that did the distributor work merely reinstalled it one tooth off.
If I were you I would remove the distributor and reinstall it one tooth counterclockwise. Take lots of pictures of what you are doing and notes of the steps you take so that you can return it to the current setting if you have to. Use a pencil or tape to mark the before alignment so that you can see that you adjusted it in the correct direction once you tighten it in place.
BTW, when you provide the timing readings in the future please state RPM and whether or not the distributor vacuum advance hose was disconnected and plugged. That will help avoid a lot of unnecessary questions.
Here are pictures of a V12 Lucas distributor showing the 14 tooth gear at the base.



It was at idle
Around 550-700
(It fluctuates)

Hmmmm that would explain some things.
Okay I have my course of action now.
Hopefully all goes well.
Thanks again!

At idle with no vacuum advance, you should be at 4-0 BTDC. If you are at 18 BTDC, then either the distributor is one tooth too advanced as Paul states, or your centrifugal advance is stuck as Kirby’s book mentions.

BTW, at idle WITH vacuum advance, 18 BTDC is not far off.

Greg makes a good point. Did you verify that your vacuum advance actually works? I use a Mityvac hand held vacuum pump. If you connect the Mityvac to the vacuum advance nipple and pump it you should see the rotor rotate.

If I were you I would verify whether or not the vacuum advance works before trying to move the distributor one tooth.