Hi

I have used 2 OBDII readers (one specifically for JLR) and no codes, no errors, no lights. Very weird.

Other than a sticky VVT, nobody I know has a clue what it is.

 

FYI, just spaying plain water to look for a leak will also change the idle speed if a leak is detected. No need to use any flammable substances.


Z

 

When you pulled the plugs does the car still have the original ignition coils? If you have one or two coils going out it could cause the type of problems you describe. You can test the coils for resistance without to much trouble. It seems you have ruled out fuel dilevery issues and air leaks so maybe its electical.I also am assuming your battery is fully charged.

 

I know a couple of coil packs have been replaced as I did that about 3 years or so ago. Good point on the others, I will check, I believe we have some spares kicking about. Even if it does not highlight the exact coil by swapping things around it may change the symptoms a little which would be an indicator.

The battery was fully charged just before recent tests, also the battery was swapped for one from another car.

A little more investigation.

Thanks

 

Ok quick update. We started taking off the coil packs and found that one had a grey wire caught under the coil pack and the bolt had pressed down sufficiently to have exposed a little copper which may have caused a potential intermittent short to earth.
Checked the wire over and it seemed ok but there is now a little electrical insulation tape over it and the cables are routed carefully away from the bolts now.
A test drive suggested everything is now ok which is a relief.

Your suggestion of coil packs helped us find this, so many thanks for that. Always worth re-checking your work.

Needs a new cam cover gasket as there is a minor oil weep from around a bolt that drips onto the exhaust which is annoying, That will be the next job then.
Cheers

 

Good catch
Has the odd noise gone away?

 

The noise is still there, but less. It is strange, I am sure I do not remember it before, but maybe I am wrong. Since the last time it was on the road we have fitted a stage 1 exhaust to the rear, but I doubt that would affect the noises at the front end.
We do not have another 4.0 here to compare it to, we have a 3.2 which behaves similarly looking into comparing them.

I am just glad to have the hesitancy gone and the overall performance back.
Cheers