I think you should start again by eliminating the possible causes, one by one. It seems to me you have two problems: (I) Rich running and (ii) running too cool.


Running too cool:
However rich, if running on all 12 cylinders, the engine will be very hot after 15 minutes ticking over at 1,000 rpm. If it is not (ie you can easily grasp the top hoses) then you have faulty thermostats or the wrong type. You need this design of thermostat:


Open up the thermostat housings and be 100% sure about this before proceeding further. Note that the smaller disc end of the stat is TOWARDS the engine, the wider disc end towards the rad.


Running too rich:
The possible causes are:
15 minute enrichment timer not timing out. Disconnect the two wires from the thermostatic switch on the A bank REAR water manifold and tape them off to prevent shorts. This will disable the timer, save fuel, and have no other effect and should be done anyway by all V12 owners! look under the rear end of the A bank inlet manifold and you will see the rear water manifold and the wires on the switch next to the heater supply hose outlet


Fuel pressure too high. Test fuel pressure and check regulators are not leaking into their manifold depression tubes.


Fuel injector duration too long or injectors not closing properly. Get the injectors cleaned (or clean them yourself, someone on here has posted a good DIY cleaning method). I am not sure how to test the duration, but again someone will know. If it is established that injector duration is the problem, then diagnosing WHY is a whole different question in itself, but at least you will know what to look for.


I think if you follow this list in this order, you will definitely get it sorted.


Greg

 

North American cars do not have the 15 min timer. The emissions systems between Canada/US cars and European cars are quite different.

 

Are you quite sure (not saying you are wrong) but the Great Palm says they did.


Greg

 

Roger Bywater is the source. Given how he was in Jaguar's emissions compliance department at the time, I believe him a lot more than I do Kirby.

A quick discussion of the differences in the emissions systems: VACUUM IGNITION ADVANCE / AJ6 Engineering

 

Thanks for putting me right on this, I had not realised it did not apply to US spec cars. I re-read Palm and in fact it is in there that it is UK and similar spec cars. Thanks again
Greg

 

so true there are two


one on each side and there are different...
and use different threads that they screw into so you will not swap them...
(which is recommended by some... though complex since you have to drill and tap the holes....)


Kirby Palm's book page 174

 

yeap we got the 45 second timer...

 

Hello all!


Well, in a bit of good news, the temp has reached normal operating temperatures! Yay! What did I do? I ran fuel injector cleaner for three half-filled tanks, seems to be using a LOT less fuel and running more smoothly.


Still, it failed emissions. For the fourth (or is it fifth) time. Still putting out unburned fuel. So, having fixed the temperature issue, I'm going to pull the plugs. If the fuel injectors were dirty, I have a feeling that they might have fouled up some spark plugs.


I did get a call from another fellow XJS owner here in CO, and they were nice enough to ask me some questions that might also rule some things out. The cat converters seem to be working well. TPS also sounds like if working as should be, with perhaps wiring harness being okay. There some other things. If the plugs don't seem to be the culprit, he offered to help me swap out an ECU and look at the vacuum lines. I am really grateful to him! (I'm not putting his username/name here for privacy)


Oh, what joy it is to spend part of your life looking at about two feet of metal.

 

Sorry, post error.

 

Just read all this thread.

Lots of good advice.
I would also be checking the TPS settings. If that thing is NOT set CORRECTLY at idle, the ECU will NOT drop into the idle fuel map, all sorts of havoc, and then if its "flaky" on the throttle rise, the fueling will be all over the shop.

Old age is at play here.

The coolant sensor on the LH side (USA drivers) is the 2 wire unit for the fueling ECU, and the 1 wire on the RH side is for the gauge.

If the ECU cannot detect a signal from that 2 wire sensor that engine will NOT start, fact. Take a running 5.3ltr HE and unolug that sensor, it will stop. If it dont the wiring is shorting internally in the loom, common.

The ECU uses vac for fuel control, so the LESS vac the richer the mixture, and obviously the MORE vac, the leaner the mixture.

The vac hose at the balance pipe in the engine bay can split, the pipe under the car can clog (partially), and the small hose twisting around the battery often splits/kinks.

Tucked away down near 5A spark plug is a fuel enrichment valve, and is commonly known as the "Blue/White" valve. This required VAC to keep the internal contacts OPEN, so the ECU operates in Closed Loop (economy), and when the vac drops (as in you accelerate), the contacts close, the ECU enrichens the fuel, and away you go, vac returns when you lift off, the contacts open, the ECU returns to economy mode, SIMPLE.

That valve FAILS, surprise, surprise, and when it does the contacts stay closed, and the engine will run "about" 15% rich.

I need a drink.

 

EXTRA Caveat:


Over fueling will kill the cats quick! Don't ask???


I dimly recall a method of cleaning sticky injectors A device sold somewhere.
The concept was to replace the fuel pump and gas. Their device provided a fuel substitute. Run the engine on it til depleted.


Some one time popular "tune up shops" touted a similar process.


Still a round, I don't know???


Or mere snake oil. I don't know.


Carl