Vibration through car at 1400rpm

[jeremy156]

Video here for the audio - would this be considered a good running sound, or not? I feel a significant vibration which seems at its peak at 1400rpm, but curious to see whether the slightly offset rhythm rings any bells for anyone with experience working with this AJ-V8 engine...?

https://youtu.be/sgKAi9ANxNs

Jeremy
X350 3.5

[J44EAG]

There sounds to be a dry tapping. Lack of cam shaft lubrication? Certainly unusual for a V8. What mileage has this car covered?

Mike K

[jeremy156]

She's covered 106,000 miles, certainly not a pensioner.

The engine oil level is good, still just under the top mark after 6,000 miles since she had a fresh dose of Fuchs 5W30 synthetic.

[J44EAG]

What year and model and does the engine have VVT solenoids on the front of the cam cover lids?

Mike

[jeremy156]

It's a 2004 3.5 V8 - VIN ending G31406.

Assuming this little fella circled blue is the VVT solenoid, then yes Is there a way to test these? Perhaps remove the electrical connector while running on either side and listen? There are no codes according to my iCarsoft LR II.

I do note a slight burnt smell when removing the oil filler cap. Assuming the solenoid relies on oil pressure, should I be looking to flush and change the oil, perhaps?

[jeremy156]

I've just disconnected each of the coil plugs in turn and each resulted in the same slight drop in revs, so presumably I can rule out coils - and the plugs were replaced only a month or so ago.

Disconnecting the wires to the two VVT solenoids has no obvious effect incidentally, but I guess that would only be notibable under load...?

[J44EAG]

VVT has oil pressure as its basis.

I always use Wynns flushing additive when oil changing. It helps to keep sludge under control and to ensure oil galleries are kept clear. If your issue is oil/VVT related, a flush plus fresh 5W30 can`t do any harm at all. As regards the noise/vibration issue, further investigations can carry on once you know you have given the engine a bit of a clear out and refreshed the oil.

Mike

[jeremy156]

Sounds like a plan. I'll flush and change the oil, listen to it again and see.

One observation I made while changing the spark plugs is that the valve cover gasket appears to be compromised on the left hand bank as the plugs were a little wet - I guess this might be leading to burning of oil and should be addressed. Wondering whether that's in my DIY capability or not... but if I do get the cover off I can look at the tensioner and VVT solenoid.

[J44EAG]

Right. That doesn`t help.

Any oil in the spark plug wells tends to find its way UP the pencil coil rubber insulators which WILL cause coil break down and misfires under engine load. This issue needs addressing as soon as possible to avoid any potential coil pack damage. I had a similar issue on a 4 litre V8 S-type where I would experience misfires at 1600 and 2300 RPM when climbing hills under open throttle conditions.

Lifting the cam covers revealed squashed rubber "spectacle seal" gaskets which were leaking and flooding oil into the spark plug wells. If you are lucky and you don`t have any coils which have been damaged and have started failing under load, you might just save the day by giving the coils and rubber boots a clean up with petrol or acetone. Obviously, the plug insulators and bottoms of the plug wells will also need a good clean. Search on the internet for the seals and new cam cover seals.

Hope that helps.

Mike

[jeremy156]

Ordering up parts for this job and it seems the bolts/gromets are no longer available AJ86865 and AJ86866.

Do you know whether these need to be replaced by default, or whether they can be re-used with care? I'm assuming by the description they include a rubber grommet which I'd expect would be spoiled, yet no alternate part number seems to exist.