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In my search for a replacement body I came across a 93 XJS coupe 4.0 Automatic. I hadn't been planning to buy a coupe because I was intentionally trying to keep the cost of entry low. Then I saw this little beauty, third owner, 116K on the clock, and all the service records from the last 10 years. I emailed the owner and asked for copies of the receipts and the big ticket items were head gasket and the rebuild of the entire rear end within the last 30K. All other maintenance was performed regularly with OEM parts.
I test drove it, verified everything worked, and bought it. Once I got it home I put it up on a lift and my love for the car only grew. Only a few minor oil leaks and the condition described and the service records honestly did describe the car.
But of course there is something to deal with. The issues it has that I knew it had when purchasing it are:
* It will need a paint job. The clear coat is going bad on all the top surfaces.
* It has a running problem at specifically the 1600-2000 rev range.
The car has been barely been driven in the past two years (estimated 200 miles) so my first inclination was fresh gas and use some cleaning additives. That first tank is now nearly empty and while the miss isn't as bad as when I started, I believe I've calculated the car's MPG to be about 8-10. If the trip computer is to be trusted the MPG goes up when under acceleration.
Idle is actually pretty decent, though it sits, I presume, low at 600 revs. If the speed is greater than 2K the is no feedback from the engine hinting at a problem.
Whatever it's worth, injector's 4, 5, & 6 seem to be more noisy than 1, 2, & 3.
I was poking around through the XJS bible "Experience in a Book" by Kirby Palm but nearly all the details about the engine were related to the V12.
I poked around on the XJ40 section since that would be the one most commonly sourced with the AJ6, but didn't immediately spot any useful information.
I presume the car is running very rich.
This morning I'm going to:
* Check the spark plugs to see if they are fouled or incorrectly gapped
* Smoke test for a vacuum leak
* Check the throttle and idle control
Any recommendation of what to keep an eye out for?
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And here is the car for your viewing pleasure. Photos are a compliment of a friend of mine.
Throttle Position Sensor could be at fault here, with the symptoms you provide. There could be a "dead spot" along the wipe that causes your issue at 1800-2000rpm.
Another possible culprit is the crankshaft position sensor.
Both are fairly common parts that can fail on the AJ16 engines. I know your engine is an AJ6, but they should be similar enough.
You should be able to get this thing sorted soon enough. Keep us posted.
Actually, if nothing more obvious pops up, I'd be tempted to send the injectors to David for cleaning. Over the years, on various cars, I've had several slight misfire-type symptoms solved by doing so.
Ok, getting back to you about the one question reveals 3 more
1.
Well, I didn't have to to finish checking everything before worship, but I borrowed a throttle position sensor off of a 93 XJ6 and at first it didn't seem to make any difference at all, but then everything cleared up. I'll give it a bit more time before giving this TPS back.
The spark plugs do need a good cleaning, but I'll get to that later today.
The intake did seem to have a bit of oil in it. Is there a PCV service that I should be performing somewhere?
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2.
I did unhook the battery to reset adaptions and now the alarm won't stop beeping at me even though it still lets me start the car and the I have full function otherwise...
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3.
Poking around underneath I notice the transmission seems to be resting quite high at the transmission mount. I realize the car has a very different transmission mount than I'm used to, but it appears like it's pushing the trans up close to the floor board.
I'm trying to get a grip on what is normal and what isn't as all familiarity lies with the V8 powered cats.
Haha, I'll get back to you in a couple hours with a few more questions I'm sure!
Unhooking the battery will not reset adaptations. Only a computer can do that. Data is stored in RAM memory, unaffected by power outages.
Just buy new spark plugs. The required Champion or NGKs are $2/each.
Regular cleaning of the Throttle Body is good maintenance. It gets gunky in there. You should get around to that sooner than later. Best to take the TB off and do a thorough cleaning on both sides of the butterfly. There's no PCV
What a beautiful looking car. The colour really suits the XJS body lines really well and haven't seen many like it. I won't get into the coupe vs. convertible debate but the coupes have a lot to recommend them (I have a '90 coupe!).
If the car has not had a lot of recent use I would watch out for water pump leaks as the gland seal dries out (I had to replace my pump). Give the car a good dose of upper cylinder lubricant and run 2 or 3 tank fulls of good quality fuel through (Shell V Power works wonders in the UK). Old brittle suspension bushes worth a look out for to.
Vee -- I did take your advice and just went ahead and got new NGK BKR6E plugs. The gap wasn't wide, they weren't warn around the electrode, and they weren't leaking compression. But a couple of the originals had some odd yellowing color around the electrode. At least I can eliminate the plugs from the equation.
VeeP -- Thank you. I do love the shade of green. I won't join the convertible/coupe debate either, but after years of convertibles, a coupe now tempts me more. I'm not sure when or why the change happened, but here I am.
I have been monitoring the car carefully for leaks. So far it only appears to be small oil leaks around the oil filler neck seat on the block, something around the distributor, and maybe the valve cover gaskets are leaking. Though, there is a coolant leak I spotted today on the right hand side under the exhaust manifold. There was a drip that pooled up on the bottom of the power steering rack, but I can't locate the source. It wasn't coming from the front of the front of the engine though.
On the suspension? I have found the radius arm bushings are both pretty warn, but the rest are in pretty decent shape.
If I remove the radius arms out to change the bushings, should they be modified or replaced to allow for installing a rear sway bar?
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More details on this running problem.
It is still present and for the most part unchanged from today's activities. The point where it is most noticeable is when in fourth gear at 50-60 mph under very light throttle. More or less throttle and the misfire goes away. I would guess two or more cylinders are not firing when it happens. Very annoying while cruising, but barely present when poking around the back roads.
It took some work, but I found that BKR5e are the direct replacement for the specified Champion RC12YC. The BKR6e are replacements for the RC9YC, which was the original spec, but a TSB later, Jag went to the hotter RC12YC spec.
From what I've read here, most people have used the BKR6e without any problem.
That's true. The coils will go bad. You'll notice that they are sold between $20 and $600 a piece. That's a big spread.
You want to make sure he coils are made in Japan. Even purchasing replacements from the dealer may not assure the quality. Bad ones will fail in less than a year. Japanese ones (made by Diamond, but you're just looking for a Made in Japan sticker) will last years. Find the Japanese ones.
I had something similar and eventually traced it to the expansion tank cap. The seal had hardened with age and wasn't doing its job so coolant blew out as the car heated up and the liquid expanded.
A new cap (make sure you get the correct pressure rating) sorted this but check your hose connections afterwards as I had to tighten a few due to the cooling system becoming properly pressurised at last.
That's true. The coils will go bad. You'll notice that they are sold between $20 and $600 a piece. That's a big spread.
You want to make sure he coils are made in Japan. Even purchasing replacements from the dealer may not assure the quality. Bad ones will fail in less than a year. Japanese ones (made by Diamond, but you're just looking for a Made in Japan sticker) will last years. Find the Japanese ones.
Ignition coil or spark plug wires? I do have the AJ6 not the AJ16.
I forget the brand of spark plug wires are installed, but they would be whatever brand Coventry West sells. The previous owner purchased the wires about three years ago and I would guess they have 300-600 miles on them. I didn't inspect them closely, but there was no visible sign of arching.
When I get the chance I will test the resistance of the wires and see if there is any variance.
Would it be worth swapping the ignition coil in the process of elimination?
Whatever it's worth: while the misfire continues, the trip computer now does register an 18 mpg average rather than the 8-10 is registered before. I assume I'm making some progress, I just don't know how much... The car is to new to me to know if the average mpg is a real number, but it's currently the only verifiable sign that something has changed.
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Leep, I will look at the coolant reservoir cap to see it's condition. I have taken it off a couple times and inspected the coolant levels, but I hadn't though to actually inspect the cap.
What is my proper pressure rating?
The car does warm up OK, but tends to run a little cool on the dial. I assume center of the dial is 90 C, if so I might be sitting at 83 c. Perhaps the car has a cooler thermostat than I'm used to? I haven't verified the engine temperature with a thermometer.
That's right, you don't have coils. I believe everyone touts Magnecore wires as the only choice, but you should do a forum search.
Replacing the thermostat might be a good cheap idea. It's probably still the original, so you may be running cool. 18mpg for an average, assuming you do some city driving, seems to be pretty good. I think you're in the right neighborhood now.
After I changed the throttle position sensor it started registering 18 mpg, which the is more than double the 8 it was registering before, even though driving it I couldn't tell a difference. This puzzles me a bit because I like to believe I would be able to tell the difference when a car is running that much better...
Maybe it was something to do with resetting the computers by unhooking the battery instead of resetting the counter on the computer in the dash?
Again, I am doubtful that the trip computer is an accurate reading, but the car is to new to me to know what the rear numbers are.
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I meant to check to see what brand the spark plug wires are, Magnecore sounds right, I believe it did start with an M, but I'll have to re-check.
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Thanks for the info on the cap. I also forgot to check that today. I will go ahead and order a thermostat though. What is the proffered temperature, 88C or 90C?
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Now that I have those questions out there, I have several more
1. How do I turn off the alarm? Ever since I unhooked the battery the first time it beeps as me every 6 seconds or some with a one note chirp. I don't know how to reset it and the remotes don't work. I have the ever important radio code, but that's it.
2. The speedo is being flaky as the outside temperature drops. When it does work it wobbles around a bit before sometimes acting like a normal speedo.
In the XJS bible they list a sensor on the rear diff as the source of the speedo for the older models, but is that still true for my year?
3. The cabin temperature doesn't get very warm even with the temperatures set to 85 F on the dial and the face temperature setting are set all the way to hot. It's warm and does get comfortable, but I never feel like I'm getting hot air directed at me.
My Volvos spoil me in this regard and are at full operating temperature in less than 5 minutes.
My spark plug wires are Rists, a brand I am not familiar with at all. They were replaced in the recent past, so I would probably check resistance before just replacing them.
My spark plug wires are Rists, a brand I am not familiar with at all. They were replaced in the recent past, so I would probably check resistance before just replacing them.
"Rists Wire" was a branch of Lucas and was an OEM supplier to Jaguar for ages. Do some digging around and you'll probably find "Rists" labels on various wiring looms.
Rists spark plug wires are fine. You shouldn't have any particular issue with them
Well, poking around the engine bay I discovered the line going to the top of the intake boot (crank case vent hose?) was loose. I had taken it off as a port to smoke test the intake, and forgot to put it back on... Operator error.
I'm puzzled how I missed that and managed to put everything else back together just fine. But now that I discovered my mistake, it does run better. Still a little rough at idle and still a little bit of a miss at slight throttle at highway speeds.
What I really need to know is how to turn off the alarm. It's been beeping at me every couple seconds whenever the battery is hooked up. Learning how to reset the alarm is the highest priority repair for this weekend!
10-18-2015, 07:06 AM
A Couple Questions on the 4.0
