1989 XJS with original 5.3 HE V12 engine with 80,000 original miles. The car was taken to the shop for regular scheduled service and to correct a couple of small oil leaks. While in the shop the engine developed a vibration which the shop has been unable to correct.

The attached list was provided at my request by the shop. It shows the steps that have been taken so far to identify and correct the vibration.

Your thoughts and comments are appreciated. Thank you, thank you very much.

 

Many mechanics dont have much experience with 12 cylinders and a dead miss can feel like a rotation vibration on a short stroke 12cyl. That said, it seems like mechanic tried their best.

Try this... hopefully this XJS has it's original exhaust. If it does... the two banks are separate.... Go around back while its running and feel the pulses at the tail pipe. Should be identical from side to side and be very smooth. If one side is pulsing and the other not then that side has the miss. Might help to find another XJS to compare it to...

If they are both smooth and almost pulse-less, then it is rotational. A well running XJS will have almost imperceptible pulses at idle, it literally feels gentle... like a cat purrrr-ing. A dead miss will create a staccato exhaust effect on one side or the other. If pusles are not dead smooth on both sides... you have a miss and its not rotational.

Check it out...maybe post a video of each side... let start there.

 

I agree with ICS....make darn sure it isn't a misfire before doing anything else.

"Anything is possible" and weird things happen but these engines are not particularly known for vibration problems. However, it is very easy to inadvertently and unknowingly disturb things when working on one....especially the type of work they were doing. There's lot's of 'stuff' in there....almost all of if baked, brittle, and ready to break. Injector wiring, for example.

This isn't a criticism of the shop.

Cheers
DD

 

I cannot see the list as it will not expand on my PC; but it having done ICSA's test on the exhaust, if it is one side, check the injector plugs very carefully. A plug that is not firing the injector, or an injector not firing, produces a very noticeable vibration.

 

icsamerica, Doug, Greg in France, thank you good people one and all for your most important comments. They are sincerely appreciated and will be forwarded to the repair shop immediately.

How should an injector wire be tested to determine if it is broken or cracked? Thank you.

Greg in France, here's the list that was attached, others may be having difficulty opening it as well:

2. REMOVED INTAKES AND VALVE COVER TO REPAIR OIL LEAKS – ALSO REPLACED VALLEY[?] COVER GASKET AND OIL SENDER.
3. CAR RAN FINE ON TEST DRIVE – SAT 4-5 DAYS – STARTED MISSING ON TEST DRIVE BEFORE RETURNING TO CUSTOMER.
4. DISTRIBUTOR CAP APPEARED TO BE CRACKED BETWEEN #1B AND #6A - REPLACED DISTRIBUTOR CAP – GOOD TEST DRIVE
5. CAR SAT OVER WEEKEND – STARTED GOOD BUT STARTED MISSING AGAIN ON TEST DRIVE – REPLACED SPARK PLUGS AND IGNITION WIRES – TEST DROVE GOOD
6. NEXT MORNING WAS MISSING ON START UP – REMOVED SPARK PLUGS TO PRESSURE TEST COOLING SYSTEM FOR COOLANT IN CYLINDERS – (WEATHER COLD OUTSIDE) – NO COOLANT IN CYLINDERS FOUND AFTER OVERNIGHT TEST – VIDEO BORESCOPE SHOWS NO SIGN OF COOLANT WASHING ANY CYLINDER BUT SHOWS CARBON ON TOP OF PISTONS.
7. SOAKED CYLINDERS OVERNIGHT WITH SEAFOAM – BLEW OUT CYLINDERS AND REPLACED SPARK PLUGS – AFTER TEST DRIVE MISS SEEMED WORSE.
8. REMOVED SPARK PLUGS AND SCOPED CYLINDERS AGAIN – CARBON GONE – PERFORMED COMPRESSION TEST – RESULTS GOOD.
9. ENGINE VACUUM GOOD
10. PERFORMED CYLINDER BALANCE TEST WITH NO PROBLEMS FOUND
11. SMOKE TESTED INTAKE WITH NO PROBLEMS FOUND
12. REMOVED FUEL RAIL AND DROP TESTED INJECTORS – ALL GOOD
13. AFTER MORE TEST DRIVING MISS HAS BECOME A VIBRATION
14. REMOVE ALL BELTS – STILL VIBRATES
15. REMOVED TORQUE CONVERTER BOLTS – STILL VIBRATES
16. HARMONIC BALANCER HAS RUBBER OUT ABOUT 3/16 ON ONE SIDE – SENT BALANCER TO BE REBUILT – STILL HAS VIBRATION
17. PROBLEM IS DEFINATELY A ROTATION VIBRATION – STARTS AND RUNS GREAT ON TEST DRIVE – VIBRATION INCREASES WITH RPM – DOES NOT GET ANY BETTER OR WORSE AFTER MULTIPLE TEST DRIVES
18. CAR ACCELERATES GREAT AND HAS PLENTY OF POWER – DRIVES GOOD OTHER THAN VIBRATION

Thank you all for your help. I'm very grateful.

 

You can check if the injectors are firing with a stethoscope;


Touch the tip to the injector top with the engine running and you will hear a clicking noise, a 60 second job to check them all.
A garage did some work on mine and when they replaced the injector leads one of the tangs had been bent over so wasn't making the circuit.
It may not be your problem but probably worth a go anyway.

 

Excellent! Thank you Steve.

 

Two suggestions if it hasn't already been mentioned: Make sure all plug wires are good. Do the pulling off of each plug wire at idle and see which one doesn't make any difference. That's the cylinder. Suspect the plug wire as I think you already said the plug was replaced as well as the cap. I was going to suggest the fuel injector test also with a stethoscope but you can use the end of a screwdriver also. Place the tip of the screwdriver on each injector and put your ear to the handle. You should hear the ticking of each injector.

 

Were you able to check the flex plate when removing torque converter bolts?

 

As this is an 89 model is it a Lucas or Marelli?

If it's Marelli a common mistake is to connect the spark plug wires in the firing order around the distributor, the Marelli dissy has a DIFFERENT wire order which should be printed on the dissy cap.

 

I re-read the symptom maybe worthwhile to check the crank damper rubber has not failed.

 

carsnplanes, baxtor,
Thank you, good suggestions, I'll definitely ask the shop to check them.

warrjon,
Thank you also for your two suggestions. I had no idea the Lucas and Marelli caps fired in different orders. When the problem first occurred, the shop and I briefly discussed the possibility of the wires inadvertently being inserted in the cap incorrectly.

Thank you again Gentlemen for your help.

 

Yes, definitely go over the firing order one more time.

 

Just to clarify....

The cylinder firing order is the same, Lucas versus Marelli. However, the *positioning of the wires on the distributor cap* is different. Sounds crazy, I know, but this is due to the dual-plane design of the Marelli cap and rotor.

Cheers
DD

 

carsnplanes, thank you.

Doug, thank you for the clarification...important difference.

 

So after all of this time, the vibration issue is still there... it's a total mystery. My mechanic doesn't know what to do next; he wanted to go into the engine, but I didn't want to gamble on more parts for an uncertain outcome. In the meantime he's decided to close his shop and has referred me to another shop. Unfortunately, the closest Jaguar dealer is 100 miles away and probably cost prohibitive. My wife and I love that beautiful car, but can't keep throwing money at it.

At this point it may be best to sell the car. Do you good people have any thoughts about all of this? Thank you, thank you very much.

 

 

So after all of this time, the vibration issue is still there... it's a total mystery. My mechanic doesn't know what to do next; he wanted to go into the engine, but I didn't want to gamble on more parts for an uncertain outcome. In the meantime he's decided to close his shop and has referred me to another shop. Unfortunately, the closest Jaguar dealer is 100 miles away and probably cost prohibitive. My wife and I love that beautiful car, but can't keep throwing money at it.




At this point it may be best to sell the car. Do you good people have any thoughts about all of this? Thank you, thank you very much.

 

I may have missed it, but no where do I see an ignition rotor replacement..

 

After reading all the posts to this thread. I would assume you are having someone else do all the checking. Are you mechanically adept yourself? If you are there are numerous, technical papers on the forum, that will lead you through the electrical / ignition system, and help you find the culprit. At the top of the forum listing, is a sticky note that tells you how to get your V12 running. And there are several others, written about the Ignition system. Kirby Palms Book comes to mind. As it covers all things XJS. If you search the forum you should be able to find quiet a bit of stuff on this subject.

Now you have to have, 3 things to make an engine run. Air/fuel, Compression, and Spark, at the correct time. A lack of any one will cause the miss. You said they ran a compression check, and that was good, on all 12 Cylinders? I would hope. So that would leave Spark, and Fuel. As a couple of the guys have said how to check the injectors, with a Mechanics Stethoscope, or a screwdriver. If they check out ok, (a loud clicking sound). Then the only thing left is the ignition. I can easily see how the wires could get crossed on a V12, as there are definitely a lot of them, in a small space. If you run the firing order, and it is correct. Pull each lead at the plug, and install a spark checker. It looks like a spark plug, with an alligator clip attached to the side, so you can ground it. I've even used an old spark plug, and opened the gap up, and simply grounded it the the engine. to test the spark. If you have a fat blue spark at all the wires, and they are routed correctly. Then the only thing else I can think of would be a faulty injector, that clicks, but is not delivering fuel. Hope this helps.

Jack