Update on the misfire issue:

Tried fuel filter which I figured would do nothing. Someone told me to try running the car and disconnecting one fuel injecor at a time, and I started by disconnecting the first two, and it seemed to make no difference. Very little if that. Does that mean that perhaps I have two bad injectors? The two that I disconnected are 5 & 6 I believe because what I hear is that the firing order is from back to front.

Perhaps they are clogged or just not working at all?

 

All injectors fire together on the XJ6 Series 3. Sequential firing did not come in until the XJ40, I believe.

 

Cylinder numbering is from front to back. Firing order is not. I think you simply meant to say cylinder numbering from front to back: 123456.

If disconnecting injectors makes no noticeable difference, then yes we would suspect those injectors of not contributing fuel. As long as those cylinders 5 and 6 have compression, spark, and injector pulse, then the injectors are probably clogged.

Injector pulse is the electric current delivered to the injector by the wiring harness to the injector. So you need to verify the connector at the injector is receiving a pulse and that it is making good connection to the injector. If the injector clicks, that is a good sign. It may click but be clogged. A LED test light that plugs into the injector connector for testing can be used to verify pulse is present. These test lights are sometimes called noid lights, and are available in the parts store's tool section.

 

On the old XK engines (such as the 4.2 found in a Ser III XJ6) the #1 cylinder is at the rear

Cheers
DD

 

Sorry, I should have double checked that, go with what Doug said.

 

Thanks guys. Do you think those fuel injector cleaning services might fix these if they are clogged? They all seem to be "clicking" but as I mentioned disconnecting the first two didn't make a difference. I put a few cans of cleaner per tank of gas in the engine but that made no difference. Perhaps the pro cleaning is what it needs?

Also, would a bad coil cause any of this? Someone mentioned this but I didn't think so, but who knows?

 

For off-the-car cleaning this outfit has a great reputation:

http://www.jaguarfuelinjectorservice.com/

For on-the-car cleaning find a shop that uses the "Motorvac", "BG", or similar injector cleaning/flushing process.

Ignition coils on these cars are known to give trouble as the years go by...but not just on one or two cylinders. If you want to replace the it on general principles any 12v coil with about 1.0 ohm primary resistance will work. I personally prefer the Lucas DLB170, however.

If your coil has an external resistor you can keep it or throw it away. Most throw it away.

Cheers
DD

 

I think the professional cleaning will have a very good chance of restoring any clogged injectors. They use an ultrasonic cleaning bath method if you take out the injectors, which is the best method. The on-car method relies on high grade cleaning solutions that are more concentrated than what you get when you mix with gas. This works well too, but if there is rust and debris clogging the injectors, the on-car method may not help. The cleaning solution is really designed to dissolve gasoline varnish deposits, as I understand it.

The off-car process allows some basic disassembly of each injector to replace little filter screens as well. And the injectors are placed in a test bench to see the spray pattern and measure flow. Bad injectors can be identified and replaced. So, basically the off-car is a bit more thorough which may be worth it in your case. But if you are not ready for all that work, the on-car professional cleaning is still a good step.

 

Thanks again for all the great info. I'm also buying a new coil to see if that is the issue. I'm sure I'll be reporting back on this soon.

What is involved in changing the belts on the alternator etc? The one on the alternator is dry rotted and on its last leg. Seems tricky, but maybe you guys can offer some advice?

Also, the rear power antenna doesn't work...not sure how to get at this. Not an emergency obviously, but just something I'd like to fix up.

 

The rear antenna is removed by first removing the rear light cluster so you can release the antenna. As I recall the motor is in the lower section of the boot (trunk) hidden by a cover. It probably needs re-lubrication.

 

The belt driven components are mounted so they can pivot and adjust the belt tension. This allows you to adjust the belt tension by pulling the belt tighter or slackening the belt to remove it. Here is some basic info on the procedure:
http://www.jag-lovers.org/newbies/se...e_service.html

From the Jim Isbell online book: The XJ6 Jaguar From Bumper to Bumper

The water pump, the air pump, (if you have a US emissions reduction system) the alternator, the power steering pump, the AC compressor and the belts and pulleys:

As I recommended earlier, all the belts should be replaced every two years, or if it is only 18 months since the last replacement and you are planning a 3000 mile trip. Never start on a long trip without near new hoses and belts. Every time I have done it I have regretted it. The extra strain of 6 to 8 hours of continuos driving daily will finish off weak hoses and belts in short order and it is no fun to be spending your vacation under a car on the side of the road or spending your vacation money on a tow truck and garage fees.

The water pump is a readily available item in most big cities in the US. It ain't
cheap, but it is available. Replacing it is, again, straightforward. The hood (bonnet) is the only problem here and it can be handled as it was in the previous section on the radiator replacement. One really nice thing, about at least the series 3, (Hey folks, I own a series 3 and that is what I go look at when I need help on writing this book) is the way the various accessories are adjusted to get the belts tight. The screw adjustable tensioners beat
the heck out of the normal US type of tensioner where you have to use a pry bar and three hands to adjust the tension. The only one that is difficult is the alternator which is only accessible from beneath the car and for which the range of acceptable belts is very narrow. For the alternator belt I suggest that you check the adjustment position on your old belt then decide if you can use a shorter or longer belt. Remember, you will have some stretching in the first couple of months of usage, so aim short. This way when you find out they don't have just the right belt you will know which way to go to get the next size. In the case of the alternator belt, ALWAYS carry the old belt
with you so you can compare the length at the counter before you walk out!

The belts can be removed and replaced without removing the fan shroud or the fan. It takes a bit of twisting and threading to get the belts around the fan blades but it can be done. If you are replacing the belts and already know you have the right belt in hand or have transportation while the Jag is down so that you can go get another if you have the wrong one (the automotive equivalent to not painting yourself into a corner or sitting on the branch you are sawing off), you can just cut the old belts and pull them out the easy way. Then you only have one set of belts to snake in around the fan blades.


Yes the antenna motor is in the center rear of the trunk, and it operates the fender mounted mast that is accessible through the taillight. Your mast segments may be stuck together and you will have to use some penetrating lubricant to help free them up. Also, you may have to remove the mast from the motor, and work the mast until the sections become free. Clean the sections thoroughly. Also, you can disassemble the antenna motor and clean/lube it as Fraser said.


More online books available here:
http://www.jag-lovers.org/xjlovers/books.html
http://cid-562a51a1e467595c.office.l...se.aspx/Jaguar

 

Hi guys:

Update on the misfire issue. Replaced the engine coil. The old coil sounded like "water" was swishing around inside. Is this normal?

Anyhow, it made very litte difference. The car still has a low speed missfire. At idle right after start it still wants to stall, and upon accelleration around 2nd gear. Mostly low speed.

Mostly everything besides injectors has been replaced. I'm trying not to spend money on injectors as they seem to be working but maybe they are clogged?

Is there a computer in this car? Could the computer be causing misfire? Not sure what else this could be on a car with 84k.

Thanks!!!

 

Yes there is a computer, mounted in the trunk. It is usually trouble free, but of course it is a possibility. I would avoid blaming the computer as it is less likely. You said it sounds like the injectors are working, but when you unplugged two of them, there was no change, so that is why we focused on the injectors. If you want to verify more clearly, use the tachometer to verify whether rpm drops or stays the same. Or use a separate digital tachometer.

If you definitely have two specific cylinders misfiring consistently, it is most likely fuel injector, spark, or base engine (valves not sealing, piston rings, anything affecting proper compression). If it is a rough idle caused by a more random misfire, it could be vacuum leaks.

I don't think we talked about vacuum leaks. There are a bunch of rubber vacuum lines that may be old and stiff. They can cause vacuum leaks that throw off the air/fuel mixture, and this is mostly noticed at idle. As soon as you open the throttle, the small amount of air from the vacuum leak is overwhelmed by the much larger amount coming through the throttle, and it becomes inconsequential. However, at idle, it causes misfire since idling uses a small amount of air, and any extra upsets the mixture.

I would suggest just replacing all of the rubber vacuum lines. If they are original they are too old to be reliable. Replacing them all will give confidence for a long time. Same idea as replacing all the rubber fuel hoses (definitely recommended).

You also have some vacuum lines under the dash that operate climate control items, and underdash vacuum leaks are not unheard of. To isolate sections of the vacuum system, you can plug off the lines at various points or plug off the vacuum source point at the engine and see if the misfire is affected.

Here are some diagrams that cover vacuum:
http://www.jag-lovers.org/xjlovers/info/XJ6Vacuum.pdf


http://www.jag-lovers.org/xjlovers/xjfaq/roughidle.htm

 

Thanks for the good replies. Lots of troubleshooting to do tomorrow.

Last but not least, I heard it could be the timing. I found an article on JagLovers that talks about how to set the timing.

Is this worth a shot?

 

If it seems to run good off idle, then timing is not really a worry. Timing problems will cause lack of power or pinging usually. But setting the timing is a good thing to do just so you know it is right and can mark it off the list. In this case I doubt it is causing the problem, but it doesn't hurt to set it and learn more about the car.

Also wanted to share a few more resources that are good to have:
http://www.jag-lovers.org/xjlovers/faqsandinfo.html

 

Hi All,

Update time again:

I took the car to a friend that works at a local garage. He used to work on jags a few years back. After some troubleshooting he believes the problem is the mass airflow meter. He claimed that when the car was idling rough and missing, he tapped the meter and it started to run ok again.

What do you all think? Could this cause such a problem?

 

A good used AFM should be easy to find and cheap.

However, I recall that you had isolated the missfire to two cylinders. A coil or AFM problem wouldn't account for a problem with just two specific cylinders.

Cheers
DD

 

I am assuming the miss is a two cyl miss, but I cannot be sure. I can say that I can feel the miss at idle and upon start it wants to stall out. After it's running for a minute or two (running as in actual driving) the stall problem ceases and it just misses slightly at idle and when you first take off between 0-25 mph you can feel a shutter then it is ok after about 30 mph.

I guess I can try the MAF to see what happens?

 

Well, I replaced the mass airflow meter and the stall is not present. The sensor seemed to help the stall issue, but not the misfire.

All injectors seem to be working properly, and all tuneup items have been done. Perhaps I am missing something? Below is what I have done.

1. Mass Airflow Meter
2. Sparkplugs and wires
3. Coolant temp sensor
4. Engine Coil
5. Distributor cap and rotor

 

Also, just curious what oil pressure should be. It's just below 40 at speed and when idle it is almost at zero. I'm assuming that isn't a good thing. Thanks.