Years of trouble free driving on my 1993 Daimler Double Six and then . . .

About four weeks ago I was driving at a leisurely 40km when my car suddenly felt as if it was loosing all velocity and engine power. Press down on accelerator pedal and nothing. Bit of what seemed like spluttering and I pulled over to the side of the road. Turned car off, restarted, and all was fine. No problems for three plus weeks.

Yesterday, driving on freeway at 80km after about 20 minutes of driving and the car seemed to "hesitate," stutter a bit. But fine. Continued on journey and parked. Driving home at a red light the car seemed to loose all power and make a guttural rumble. Put in park and pressed down on accelerator. Much greater spluttering, almost felt like car would backfire, as if it was missing. Light turned green and I put the car in drive and proceeded slowly, with car sputtering initially and then fine. Came to next stop light and car seemed to loose power even more rapidly. Pulled over, turned car off. Restarted, and it seemed to take longer for the car to drive "normally" from slow speed.

Parked car at home.

Today, started car up and drove around the block (5 minute trip), and no problems.

 

My initial thought was that one of two ignition coils is on the way to carking it.

Would the symptoms I have experienced fit the diagnosis?

 

The B bank injectors became intermittent in my X305, causing a similar loss of power. There was no attendant unburned hydrocarbon smell at the tailpipe, of course, as there would be if ignition was the fault.

Eventually, the ECU was discovered to be water damaged, and a used replacement ECU was the fix. Not sure about the XJ81, but the X300/X305 ECU location is prone to water ingress.

 

If the distributor rotors are of similar design to the XJ40, i.e. they contain a resistor, I would check those first for high resistance.

 

Sounds like classic Magneti distributor failure. The distributor rotor fails, and cuts spark to the B bank. Because it is a V12 it runs smoothly (as a straight 6) but has no power. IDK if your car has cats, but dumping raw fuel into hot catalytic converters is how a bunch of XJ-Ss have burned up. If you look for "Magneti distributor failure" or something like it you'll find lots more information on it.

 

Although the XJ40 doesn't have that type of distributor, I believe the unit the previous poster is referring to is also more commonly known as the Marelli distributor.

 

The distributor manufacturer is Magneti Marelli, so I've seen it called both.

The XJ40 does not have that distrubutor, no. But OPs car is a Daimler Double Six, so an X81 V12, which does have it.

 

Problem resolved: the fuel injector loom was the issue. Purchased a very good second hand loom and the spluttering vanished. The coating on the wires right next to the injectors was peeling off as the loom came off.

In hindsight, I realize that I have been dealing with this issue for a number of years; one fuel injector was not always performing. It was most noticeable at a traffic light if I had the AC going after a long(ish) drive.