Top 20 2006 Jaguar XJ8 L - Page 8 Questions & Answers

Follow the top radiator hose to the engine, it's connected to the thermostat housing, the thermostat is in that housing.

I think you've called your solution, knock sensor!

What is a knock sensor?
A knock sensor is a low voltage producing device (a signal producer) that allows your vehicle to run at the very peak of advanced engine timing without allowing very damaging engine knock caused by cylinder pre-ignition. Today's motors have high output or horsepower and have very low quality gas to run them. The engine knows that the fastest way to increase performance is to automatically advance the timing. The knock sensor lets the ECU know when knocking occurs so it can ****** the timing a bit and stay at the maximum RPM's possible without damaging the engine.
How does it work?
The knock sensor is located in the engine valve or cylinder at the back of the motor or it can be located in the intake manifold close to the point where it connects to the engine block. Seated in these positions next to the cylinder, the sensor can feel the vibration of engine knocking caused by costly pre-ignition. Feeling the vibration, it emits a small voltage charge that is transmitted back to the ECU. The ECU, now understanding that the engine knock is occurring, retards the timing until the sensor does not feel any further vibrations.
Is engine knock really that bad?
Engine knock is definitely bad. The knocking is created by the ignition of fuel and air inside the cylinder before the valve reaches the highest point of the rotation where combustion is supposed to occur. At the minor end of the spectrum, this causes inefficient gas use and rough idle or vibration while driving. On the more severe side, this ignition of fuel can cause very costly wear and burn damage to cylinder heads, the cylinders themselves, gaskets, and pistons. Repairs can easily get into the thousands of dollars.
Does the knock sensor do anything else?
Because of its function of only reducing the timing of the ignition at the point there is a knock, the sensor allows your ECU to push your timing to the very edge of it's performance without costly damage to your motor. This translates into more efficient fuel consumption, better horsepower, and longer engine life.
How will I know if I have a faulty knock sensor?
We're not being funny here, but you would experience engine knocking and vibration. The knocking can become increasingly loud where you can hear it over your engine noise. If that doesn't happen, you will experience rough acceleration with a jerking sensation like you are hitting a speed limiter. You may also experience misfires, backfires, or smell a strong engine exhaust or burning smell from the pre-ignition happening in the cylinders.

there are a few other things that can cause a clicking and knocking noise . first is valve tapping which is when the valves become a little loose and the noise you hear is when the gap is taken up and the metal taps, second is that the bearings in your water pump may be starting to fail, and third might just be that your belt has a bad spot and clicks as it passes a certain pulley.
This will help. Thanks please keep updated. please do rate the solution positively .thank you for using fixya.

Most likely is thermostat failure (stuck closed).
However the water pump may be damaged.
Does the air heat up when driving? this would indicate a malfunctioning pump or clogged core.

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this vehicle needs 95octane unleaded fuel ,and put more than 5 litres in because it will use a litre to start up .The noise on start up could be the hydraulic tappets because it need a good oil change and a tin of stp .The stability control will come on if the engine isnt running because it has lost pressure to the system that keeps the car level when cornering .Put some more petrol in say 20 litres and try it again because i dont think you have enough fuel in the tank to allow it pump up and return without causing a airlock

If this occurs regardless if you are moving or idling, check first the oil level on your engine. An incorrect oil viscosity or low oil levels may cause the engine to be noisy. Low grade fuel may also cause this but if you have filled up with virtually the same fuel, have the ignition timing checked out. Other than that it may be the knock sensor that may have gone bad
(usually located on top of the car near the intake manifold) or a problem with your valve train.

You have to find it the moment it does NOT start, few things, batt/starter/solenoid/ignition switch could be at fault. If you say starting it means DOES NOT TURN OVER ? Or turns over but does not want to run??

first check the level of your anti-freeze when the car is cold it sounds like it is low and that could cause no heat. this is because of the leak you see! for the leak can you tell me what area it is in front of motor or back of motor? where under the car does it hit on the ground? it will beter help me to help you. but could be the water pump or radiator hose most comon for these cars. let me know and add anti freeze if it needs it.

just a guess on this but but have you tried resetting the computer for the switch?

http://jeg.serverhouse.com/Jag_docs/Timingchain.pdf

Here it will show how to do the job step by step.

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Try pumping the accelarator about 4 times before cranking it over. If that doesn't work prime with some fresh fuel and it should start up.

You need to check and make sure that your head gasket isn't cracked and you are leaking coolant into the engine oil. If it is cracked you could cause yourself some serious problems in the near future. You can check the oil and see if there is water or if the oil looks kinda like chocolate milk. If you don't see that you might want to take it to a mechanic and have them check it with a pressure test to see where the leak is. I would just strongly suggest not messing around with this since you can't see where it is leaking. Check this asap, I just don't want to see you ruin your engine. Thanks for using FixYa!

What type of problems, be more specific?

Hi,

Does it seem to crank really slow if your not able to turn the motor over at a high enough rpm it will not be able to start or will take a long time.
along with that your temperture sensor for your cold start injecton could be bad not sending the signal to your car to inject the extra fuel it needs to start in cold wether along with even the wire to the cold start could be loose and not conecting all the way check to insure that that all wires are conected corectly and securly also try another temperature sensor for the engine controls i believe that you have two sensorse for temp one for our gauge and one for engine controls if the sensor dont work let me know but chances are its either that or a starter.

If it just cranks and won't start,
then i am 98 percent sure that it is the temp. sensor for the cold start its not reading that its cold so its not giving the extra fuel kinda like a choke does on a carbed vehicle ensure wires are secure and replace temp sensor.

Hope i helped you.

Thanks for using ' Fixya ' and have a nice day!!

Disconnect the multi plug behind the left headlamp and also all plug connectors on abs sensors behind discs and spray with wd 40, Shazoom all lights go and problem solved.

hi do you hear a click sound from the gear lever area when you press the brake pedal if not first of all check under the dashboard around the brake pedal se if the brake switch has fallen out if all looks ok then if you look at the top of your gear selecter you should see a small plastic screw remove it with a flat screw driver put you car key in the hole and push down on the key you should be able to then remove your gear selecta from the park position hope this helps

Yes it is a good deal

the fact that you have to put oil in the cylinders indicates there is little compression. The bushings are knocking also . you will have to overhaul the engine. Or rebuild it.

Welcome to Fixya! The ticking sound is Correct and will not hurt anything at all. The Light on the Dash Could be caused by a Clogged Radiator or a Slow Water Pump. I would have these Checked out to see if they are ok.

Unfortunately theres not a lot you can do with them. If you are sure the battery is OK and the contacts are clean and it still doesn't work then a trip to the dealers to get it reprogrammed or replaced is in order.
Can you see any moisture inside? any chance you dropped it in the rain by accident?
If by any chance it has come into contact with moisture try drying it out somewhere warm but not hot as that may cause more damage.