Well after 6 years of flawless running the XJS God's have frowned on me. About three months ago I came out of a store and the car ran rough after start, would idle lopey and hesitate on acceleration. Went home and later restarted and all was fine. A month after that it did it again so I went out and changed the fuel filter and all seemed well, drove it bunches, took it to and from Amelia last weekend (3 hour round trip) no problems.

Yesterday I took it out for gas and after I got gas I started it and it did it again. Took it for a drive and it would run fine at speed but idle rough and hesitate on acceleration, valve flutter and the temp gauge went up more then normal.

It must be stated that when it would do it it would perform great in N or P but not D.

Today I decided I'd check the advance so I pulled all the wires from the cap, no problems, both advances work great and are free. All plumbing looks intact.

Started it up after cap install and it did the same thing. I then proceded to change out to a known good ignition amp, same result. I went to check sump tank and it's clean with no problems but after that it will barely run at all now! Runs super rich, stalls, barely idles in P, N and stalls out in D.

Pulled all the under hood harnesses and cleaned all connectors, checked all vacuum hoses, checked ecu vacuum. I'm at a loss, the problem has gone from bad to worse!!! All injectors are firing. I'm stumped.

 

Good diagnosis there, and that helps a lot.

I do hope you took time to sit on that stool and have a drink or 2??.

I am thinking either:

FPR (Fuel Pressure Regulator), particularly the LH one, but both if the RH is still fitted. Pull the vac hose/s, and note any raw fuel in there, which is the "usual" sign of a failed diaphragm.

The TPS (Throttle Position Sensor), has gone legs up. It does have all the signs of one going bad, and now gone bad. Probing the wires with a DVM will tell all.

Fuel pump getting tired. If the age of the pump is unknown, then replacement will do no harm, even if it fails to sort it.

The 2 throttle bodies are all gunked up.

The electrical connector of the EFI resistor pack, bolted to the panel in the engine bay behind the RH headlamp bowl. Greg in France has done an excellant write on that particular item, and the fix that actually works. It is included in the "stickies" at the top of this section I believe.

There may be more, but that will occupy you for a few minutes.

 

Plugs, HT wires, coils changed yet? Must be electrical, I think.

Also, carefully check the integrity of the low tension wires to the coil; as the copper fractures inside the insulation just short of the actual connector. In fact, a very good plan to replace the connectors to the coil from the ignition amp. Plenty of wire there, cheap to do.

Also the twin wires from the bottom of the dizzy that plug into the side of the amp need checking carefully for shorts etc. there is a plug halfway along them to clean too. Also, just could, repeat could be the magnetic pickup inside the dizzy that is triggered by the starwheel. But this is a last resort change I think!

My money is on one of the above, but anyway needs doing to eliminate possibilities.
Good luck

Greg

 

I've got a coil on order, mine is now the single coil set up and all the connectors were checked and are solid. My throttle butterflies are both spotless and I checked the resistor pack connectors. When it did it while on the road and would perform, idle perfect in "p" but stumble and valve flutter in "d" it reminded me of an ignition failure under load. Now with it barley running in P or D it's got me baffled. I also pulled both fuel pressure reg vacuum hose last night while it was running and there's no sign of fuel in them.

 

Do a fuel pressure check. Then quality of fuel. Inconsistent problem could be a fuel problem. Check drain in fuel filler to be sure it flows away from tank opening. With the weather we have had this last winter water gets everywhere. Took a friend 3 times taking fuel tank out of boat until he realized the small station he had been getting fuel had water in tanks. Went to a station higher and to a marine fuel station and eliminated the problem. Changing filter once and it went away, might need to change again and again until tank cleaned out.

 

Did you happen to empty the filter contents into a clean jar? If so, what did you see?



Just for the heck of it pull the filter and empty it. It'll only take a few minutes. If there's a problem with the gas you'll likely see it.

Cheers
DD

 

Sounds like every time you do something with the gas it gets messed up. What kind of gas are you putting in it?

To me it sounds like any time you do something with the gas you are stirring the tank, and changing the filter helped last time, so it sounds like your tank has a bunch of crap in it and it clogs the filters.

Get your tank below half, pop out the sending unit, and inspect the bottom and sides of the tank.

 

I did doug (habit of mine to cut the old filter open) pretty much just normal staining on the paper element, no water. It only did it once the other day after gassing it up, not during any other time. I run Shell premium in all my cars from the same station ( 6 total cars in the family ) no problems on any others fuel wise so no reason to suspect that, sump tank clean, old filter clean, I'm ruling out fuel contaminate.

 

Threw the cover over it today and it's repair is on hiatus. I ordered a new coil AND original Delco Remy D1609 module. After talking with my electrical engineer in the simulator bldg this morning he said the coil failing will have implications on the amp module. He said if the one I put on to test was older and the coil was continually shorting internally it would take out the amp pretty quick. All indicators lead me to the coil/amp combo.

It was intermittent, wouldn't work under load, then progressivly got worse esp after installing the older amp. I'm not leaning towards the TPS solely because it was fine in "p" and "N" but not "D" intially.......the TPS seeming sees capstan/throttle movement but should care if the car is in gear, ignition is very suseptable to be load unfriendly unless all components are working properly.

If I jump feet first now like I did last night I'll be chasing my tail and as they say 50% of your maintenance is caused by 50% of your maintenance. I'm going to wait on those two items and at least eliminate them from the checklist before i trudge forward.

I'll report back in a few days when they get here.

 

While you are waiting.

Inside the AMP is a small condensor looking thing in 1 corner, and held down by a small "Philips" screw. Remove it, throw it away.

These things "leak" to earth and reek havoc. I have removed 9+ now and no ill effects at all. It is a "noise suppressor"??? as far as any electrickery nerds can determine.

My HEnear drove me nuts, more than my usual mode, many years ago, and that damn thing was the culprtit, and NOT the module at all.

 

I noticed two separate devices as such, one is a condensor sitting horizontally the other appears to be a zenor diode sitting straight up/down. I have the amp box apart on the work bench now so that'll be easy to get to. Which pins do I need to put the volt meter leads on the tps junction to get a reading, and do you have to numbers handy? Won't hurt to read it out, thanks for your help.

 

The probe is the Red and Green, I THINK.

Ign ON, NO engine running.

You are looking for 0.32V - 0.36V at the idle stop position. I always get it at 0.34V, and I am not that clever, so it is simple, really.

Once you got it set, bolt that TPS capstan back down and check it again. If the Jaguar Gods are with you it will NOT have moved, bet it does, mine always do, so mess with it a few times you must.

Some DCM have too much damping to show a flaky TPS, so I revert to an old school Analogue meter I have, and the needle swing is really easy to see.

You are looking for somewhere near 5V at WOT (Wide Open Throttle), but please dont get fussy with WOT readings, as long it 4.?? the V12 will never know.

 

Why no public profile on you??
RagJag

 

You've asked this before, why do you care so much AND what I do on the Internet and what I show as public information is MY business. I'm trying to sort out my car here and help others, quit stalking my profile and quit playing forum police.

 

Thanks for the info Grant (and no, I don't know if you have a public profile and I really don t care ) I'll check it later or tomorrow ( the TPS that is) I just got back from conducting our clubs British Car Road Rallye, I'm quite bushed, a nap and adult beverage are in my future!

 

My digital voltmeter is a POS at best but probing the red wire I get 38 to 41 at idle position and 4.88 at WOT, I'll borrow my neighbors analogue one tomorrow, but it really doesn't seem way off spec to be acting the way the car does.

 

It is too high, the ECU will NOT drop into the idle fuel maps at that settings.

It is that critical.

Unstable idle will drive you nuts at that high setting.

 

Success! Changed out the coil (new coil) and module (NOS Delco Remy NOT aftermarket) Fired car up...................runs like a champ! (where's some wood to knock on!) Drove 5 miles, shut her down, let sit, re-fired......no problems.

"Disclaimer"...this is in NO WAY intended to deter, poo poo, or be critical of anyone's advice here...it is GREATLY appreciated AND there are some amazing and pure geniuses here......

.....that being said, be very careful of diving in feet first when there is a "running" problem, ie, fix one thing and try the car....if the car's "down" be careful of running through a mired of items because you want to know "what" fixed it and you want to make sure you don't further complicate matters by fiddling something loose or off kilter that will further frustrate you.

In my case the problem was intermittent, then worse, then OMG it won't even idle. I checked the advance, no joy, checked the sump, no joy, checked harness connections, no joy, replaced the module with a known good, older one...some initial success then rapid failure. I deduced it was the coil intermittently failing then complete failure which quickly toasted the older module.

I resisted the urge to fiddle with anything until the module and coil arrived. Once here yesterday I went out and put them on, VIOLA! fixed. never touched the coaxial, TPS etc until I knew what I suspected was off the list then I would move on one item at a time from there. Over doing trouble shooting w/o the ability to "check" functionality after each item begins a "chasing your tail" mentality where you start to wonder and question everything you've done..

If my problem reappears soon then I'll move over to an intermittent TPS failure and replace that and then re-check, fingers crossed I've resolved the issue.

Thanks to all who have provided help and insight, you're input has been invaluable in getting my car back on the road and is what makes this a great place to hang out. Cheers!

 

Very well done. So basically it was coil? Great result. Wonderful feeling when you fix them, isn't it!
Greg

 

HaHA!!!! Spoke too soon! 3rd time wasn't a charm! Went out after she cooled for an hour our so and it's right back! It's doing what it did before, chugs in gear but pretty good in "P" and "N". So at least I know what it wasn't . My TPS is reading a solid 34 to maybe 36 at idle so I really don't think that's it. I'm pretty sure I've ruled out ignition, I'm thinking of moving towards fuel delivery, maybe pump dying? I'm going to go out for grins and pull the condensor wire in the amp and check my coaxil wire end then reattempt.