I have had a 1973 E type series III for many years. The V12 has been very reliable, very strong.

Several years ago the original ignition module and fuel pump quit. I replaced the ignition module with a Crane system and replaced the fuel pump with a generic fuel pump with a fuel pressure regulator. For several years thereafter, the performance was virtually perfect.

A year or so ago it developed a slight miss when hot (run 30 min) and under a heavy load. Initially I thought it might have been a fuel issue because pulling out the choke out seemed to help.

The problem has gotten progressively worse and worse to the point where now it will start perfectly, run very well when cold but as soon as it begins to warm up (~5 min in the garage) will miss If the RPM is slowly raised with no load there is no miss. When under a load (even rapid RPM increase when not in motion) the miss is now very bad

It probably is something related to the ignition system because using an old in line light set up between the distributor and the plugs, the intensity is normal and constant until the problem begins and then the intensity decreases significantly and is inconsistent

I have taken the following steps
?À Replaced the coil
?À Replaced the plugs
?À Replaced the wires
?À Replaced the distributor cap
?À And ultimately replaced the Crane system even though everyone assured me that this behavior is not associated with an electronic module failure.
?À Removed disassembled and examined carburetors nothing obvious
?À Looked for vacuum leaks all over the engine with starter fluid
?À Replaced fuel filter
?À And everything else I could think of

I'm really out of ideas. I have had several professional mechanics look at it, some with extensive Series III experience. Any and all suggestions would be greatly appreciated. The car is not drivable now and I really miss it.

Thank You
Regards Bruce

Submitted by donander@us.ibm.com on Tue, 07/07/2009 - 18:18

Bruce, You might want to check the distributor shaft for excessive play or the driving gear being loose. I had a similar poblem on my 6 cylinder with points and replaced the whole distributor with a Pertronix electronic one. I don't think they make a V12 version. If there is enough wobble the pick-up may not be accurately sensing when to fire. Don

Submitted by SC38-21185J on Tue, 07/07/2009 - 18:01

I am not a V-12 owner, so this is just a shot in the dark. But I've always heard that the electronic modules, especially when nestled on the engine, are susceptable to heat problems. Perhaps when the car starts missing, get some canned air and try cooling the module just to see if that has a momentary affect.

Do you still rotate the distributor to change timing on a V-12? Might try that as well.

Make sure your gas cap is venting; perhaps run with it loose.

Sorry, no expert here.

P