Hi


Could I get your opinions on what could be the cause of the noise and miss fire on my XJ8 please? Sorry for the long post.




Everything was running smoothly until Friday morning. I noticed it was a little rough when it was started but just put it down to being cold. I drove to work, about 50 miles on B roads, due to rough roads did not notice anything different. Once I got to a section of dual carriage way and I was cruising with light use of the accelerator pedal I noticed a slight vibration. Once stopped at work it was obvious that the idle was pretty rough. I checked for OBD codes but it was clear.


I ran steady home that night it drove fine up to 55mph then stated to miss fire a little so I just took it steady. Idling is lumpy and there is a high pitch electrical type whistle and a rubbing noise. The video is pretty much an exact replication of the sound.


I've taken each of the coil packs out and checked them, physically nothing stands out. There is no oil in the plug wells. I have checked best I can the breathers and pipe work from the air box to the throttle body. All the injectors seem to be firing correctly. I've used a big screwdriver on each and put an ear against it and the noise does not seem to be from them. The noise also does not seem to be from the timing chain / cam sprocket areas. It does seem louder from the water pump area. All tested using ear and big screw driver. I've taken the belt off and checked the water pump and other pulleys and started it up for a few seconds and the noise is still there. So that rules anything belt driven out.


From more reading and searching I have possibly come to the conclusion it may be the timing chain(s). I haven't popped off the cam covers yet.


Above 1000rpm it runs smoothly apart from the noise, the miss fire is a lot less.


Anything I have been thinking about can't explain the noise only the miss fire.


Thanks

 

If the secondary tensioners have not been replaced remove the cam covers and check them. It is very possible one of the exhaust cams has skipped a tooth.

Do not attempt to start the engine again, you could right on the edge of a big expensive mess.

Rotate the engine clockwise from the front using a 24mm socket and breaker bar until you can see if the flats on the camshafts line up.

 

Thanks RJ, I'll open them up and take a look.

 

I think I have found the problem. RJ, I didn't rotate the engine as I could tell this was it.

I do believe the top is missing off this!


Clicking noise and rumble metal chain on metal tensioner.

It looks to have over extended pushing the chain up and moving the position of the timing. I don't think its jumped as well. You can see the right hand cam in the picture is approx. 1/4 inch further over going by the flat sections and the bolts in front.

The right hand side looks fine


The primaries also look fine. This is the left hand bank.


The red underlined bit is a chunk of the top of the secondary. The cross is nothing but a bit of sealant.

I'm not going to leave it as it all looks fine they will all be changed but I think the cause is limited to the secondary on the left hand bank.


Thanks for your help, on to sort it out now!

 

Just to finish off the post and not leave it hanging...


As I didn't want to commit to a full on replacement on all chains and tensioners before making sure there was nothing else at fault. I decided just to change the left hand tensioner and the secondary chain first.


I fired it up and all is running smoothly.


I'm now going to do the lot, primaries and secondary's. I'm also going for a new water pump, thermostat and serpentine belt tensioner.


Thanks for your help.

 

Just to make it more difficult, the missing pieces are in the pan and will end up in the oil pump pickup screen, where they could reduce flow.

As I recall, the XJ8 pan removal is not easy like the XK8, but the risk would have me concerned.

 

Another Jaguar owner that deserves to own and love a Jaguar.

 

RJ - I forgot to say the pan is coming off to search for the AWOL plastic parts. From what I saw while under there the other day access looks ok.


Thanks Test Point

 

I dropped the oil pan today and picked out enough bits of tensioner plastic to just about make up the missing part. About half was in the pan and half was in the oil pick up.


I found both primary fixed guides had massive cracks through the middle, very please I did not just do the secondary's and leave it there. The primary tensioners looked OK but were binned anyway. The other secondary tensioner had a massive split down the middle of the body but that was expected seeing other peoples images.


Nearly back together now

 

Play the lottery! It looks like luck is with you finding this all before a valve crash.