Hi all,
My 1999 jaguar xj8 has developed a problem.
was running fine,but now the engine shakes on tickover
as if the coil packs are playing up?

no fault codes or engine light on.

car is ok if you rev past 1000 revs,but when you return to tickover
the engine shakes and you can feel this in the car!

could it be a broken chain tensioner?

any help would be appreciated to say the least
as i don't want to damage the engine!

engine has done 75000 miles and was very sweet

the fault just happend on start up one day

regards charlie

 

Bump..........Anyone???

 

Hate to be the one to say it, but, pull the cam covers and look at the tensioners. Look very closely, or better yet, replace them while you're at it. This is of course assuming that they have not been replaced.

 

Wait a minute, there are things that you should check before. If the car truly misfires then you should get a fault code eventually. A code reader can also read some basic OBD2 pids. Before you get in trouble and take the valve covers off check for simpler things. I've never seen a Jag with broken chain tensioners run fine at 1000rpm.

This is what you do:
1. Duplicate the problem as much as you can and check for fault codes, if you get one then good we go from there.
2. If you dont get codes then remove a couple of spark plugs, and look at them. What's the gap? Do they look ok? They should have a whitish powder on covering them, if they are black, or they are wet, that means the car is misfiring and not burning all the fuel.
3. Air filter and throttle body clean?
4. MAF clean?

I could keep going but these are the basics. If you take the valvecover out and everything is fine and later you found out it was a dirty throttle body you'll be mad.

I reiterate, I have never seen a car with broken tensioners smooth out at 1000rpm, that doesn't make sense.

 

I had the same problem,

 

I had the same problem, and no check engine and no warning lights, I was pretty shure that it is tensioner problem and I was wright. when chain jumps one teeth you get missfire. takeoff valve covers and check the chains if they are loose then you'll have to do tensioner thing, I would sugest doing all chains and tensioners job...
and yes it runs, lets say, fine at 1000rpm but if you push it to 2500 or 3000rpm on drive then you'll se that cat feels really bad (don't do it) at 1000rpm you just make the shaking faster so you don't feel it and when on idle it feels like someone is shaking the car from outside?
sorry but I really don't think it's ignition coil...

 

If you're not afraid of accumulating some errors on the car's computer, you can easily check if the problem is coming from the coils/spark plugs. Just start the engine, let it idle until it starts shaking, then open the engine bay and start disconnecting the coils, removing only one at a time, going through each one... and discover how the work of the engine changes. If you remove one of the coils and the engine continues working without any change (without getting worse) then you know where the problem is coming from Don't worry - there is nothing bad you can do to your car, but anyway - be careful while doing this!!!
I'm sure there are many other ways to check the coils and the spark plugs, but this method doesn't require any special tools, knowledge or time.

If it's not a problem with the coils, check the throttle body... unstable work of the engine (shakes) can be caused by dirt inside the it and it's always good to clean it.

 

key here......you answered your own question.....

"the fault just happened on start up one day"

Start-up is when tensioners fail. Suggest removal of the cam covers and check the timing chain tensioners.

I wouldn't start the car until this is done

 

2003 XJ8 here. I have a similar problem. How severe is the shake? Mine is shaking slightly when I startup and idle in park. Cleaned throttle body, replaced air filter. Next step is to clean out part-load breather connection and possibly new spark plugs. Is it possible for tensioners to be a problem for me even though mine is '03?

 

Your car came with the metal tensioners and we have never had a reported failure with them.

For lack of mention I assume you have no CEL.

Just thinking:

Part load breather cleaning, throttle body cleaning, MAFS cleaning, spark plugs, coils, air filter. What is you idle RPM's? Should be around 550. Throttle Position Sensor not reporting correctly.

Beyond that you are getting into compression. How many miles on the car?

 

I bought this car in December with ~90,000 miles on it and I don't have a lot of history on it so I am trying to be extra picky about anything that indicates a problem.

No CEL. On cold weather startup, 1300 RPM for 10 sec; drops to 950 while in park. Idles at 550 after warming up. Cleaned MAFS, part-load breather orifice, throttle body, and replaced air filter (working through the cheap stuff). Bought some Ngk Ix Iridium (BKR5EIX-11 ) spark plugs, have not installed them.

I may be concerned over nothing as the shaking I experience is slight, intermittent, an only while the car is warming up. I am pretty inexperienced in doing my own maintenance and need all the advice I can get!

 

Just another thought, do you have any click noise? I have a lifter click when cold. rev up some goes away, but still minor like miss when at idle cold or hot. rev above idle, smooth as can be. I have listened to tailpipe sound and put put from drivers side at idle.

Kind of bothered me , but mechanic said it happens and live with it or spend bunch of money to go inside engine.

Good Luck

 

Clarification to readers ...

The comment applies to mockjr with a 2002 but not to charlie2265 with a 1999.

 

I don't think I have any clicks. Are you experiencing a rapid click or an intermittant click? I will listen carefully tomorrow when I change out the spark plugs. Thanks!

 

Open the hood and find a hollow piece of tubing or metal rod and put it on the valve cover while at idle and put ear on end of the rod to listen for a fairly slow click, If so move it from front to back to find loudest. Do the same on both sides. If no clicking then some other problem as others have suggested. Good Luck

 

Many thanks to all that replied,The fault was that one of the top timing chain tensioners had failed,exhaust cam shaft had jumped one tooth on the sproket.
The car has had the full kit fitted,new chains, tesioners and guides
all is now well with the car,once again many thanks to all and best wishes
to all jaguar owners.
regards charlie

 

Good for you.

It's always nice to hear the final resolution for a specific problem as it helps readers figure out what the reported symptoms point at.

 

I'm both glad to hear some information over the subject and a little scared about the reasons on your car.

Can you tell me how exactly did you found out that the cam shaft has slipped a tooth?

 

A follow up is always appreciated charlie, thanks for adding to the forum knowledgebase!

 

[quote=Estilian;503074]I'm both glad to hear some information over the subject and a little scared about the reasons on your car.

Hi,I removed the cam covers and found that one of the top tensioners
had broken at the bottom,plastic part of the tensioner had come off and went around the inside of the chain causing the exhaust cam sprocket chain to jump a tooth,this was confirmed by the mechanic who did the repair.hope this helps you

best regards
charlie