Thread: Flashing check engine light Discovery 3S 4.0 V6

200,000km mate.
I just can't reconcile the absence of any code indicating a cam/crank timing mismatch that would be enough to cause a misfire.
I might take it home and play investigator myself.

Rereading the thread, your codes indicate a "misfire". Now a misfire can be heard, and felt by the engine rocking etc so do you actually hear it misfire as you indicate it is smooth when revved and to be smooth all cylinders are working.
The ECM controls spark based on Engine load, Engine temperature, The knock control function, On automatic transmission models, the shift control function, The idle speed control function.
You changed the gearbox and the shift control is an input to the ECM. If a cat is blocked it can be felt at the exhaust with your hand over the exhaust outlet
Just trying to understand the problem, Is fuse 17E in the battery box good as this powers the capacitor for the ignition

There is a feeling of misfire, though not rough running condition, except maybe arguable at idle. Revs cleanly and can be driven.
The only codes are for misfires all on the one bank.
The left and right banks exhaust share common mufflers though in a design that would make an asymmetrical exhaust feel noticeable, and each pipe feels similar. It smells strongly of unburnt fuel consistent with the rich condition.

A well known LR independent in Adelaide have spent a few hours examining the car and are pretty convinced the timing chain has reached the point of no return. They feel strongly that the cats are ok given that there are no O2 codes with new sensors, and that either end of the cats look fine. This is contrary to a few members on this thread that have expressed strong concern for cat failure based on multiple experiences.

I can't quite rationalise the sudden failure that on resetting the faults immediately trips to fault again, unless a plastic chain guide has failed and the chain became suddenly loose. This would account for the noise also.

I had a similar thing with a Porsche once. They use an interference fit for the cam wheels onto the camshaft. One slipped when I spun the car during an event (engine went backwards). It wasn’t running too bad but couldn’t pass the MOT for exhaust emissions. After trying everything they removed the engine and checked the cam timing and low and behold, it was out.

Originally Posted by Julian B

A well known LR independent in Adelaide have spent a few hours examining the car and are pretty convinced the timing chain has reached the point of no return.

If you are happy with this independent then you have no option but to trust their judgement - however in my experience many repairers diagnose by replacement and charge the customer accordingly. So they will refund all costs if the chain is replaced and the problem continues?

If it is a chain then valve timing should be getting out of specs and the ECU cannot compensate spark to cope - won't the codes show this up? I dont know but is the sort of things I would be asking.

However, I appreciate that in many cases there are no options when stuck - I guess it is a judgement call.

Good luck with it.

A timing chain rattle is very noticeable and engine would have running problems - not a smooth running engine. I would still be looking for electrical problems like an earth for that bank of ignition coils on the side giving the "misfire" symptoms. If no codes where showing up would you suspect anything wrong? Another thought is have you done a hard reset (battery leads off and linked together). As you say the exhaust smells"rich", have you removed a plug on the "faulty" side and see if its really sooty.

Originally Posted by garrycol

If you are happy with this independent then you have no option but to trust their judgement - however in my experience many repairers diagnose by replacement and charge the customer accordingly. So they will refund all costs if the chain is replaced and the problem continues?

If it is a chain then valve timing should be getting out of specs and the ECU cannot compensate spark to cope - won't the codes show this up? I dont know but is the sort of things I would be asking.

Good luck with it.

The independent is not keen on the replace-parts-until-fault-resolves method, and their reputation is good. The issue with this Ford motor is that it is ultimately foreign to LR and although they agree that the absence of a timing mismatch code is odd, they have seen similar absence of codes in other cases for this motor.

Originally Posted by Globetrotter

A timing chain rattle is very noticeable and engine would have running problems - not a smooth running engine. I would still be looking for electrical problems like an earth for that bank of ignition coils on the side giving the "misfire" symptoms. If no codes where showing up would you suspect anything wrong? Another thought is have you done a hard reset (battery leads off and linked together). As you say the exhaust smells"rich", have you removed a plug on the "faulty" side and see if its really sooty.

The noise is subtle mostly when lifting off the gas in neutral. It runs roughish on idle but revs cleanly. I have done multiple hard resets to no avail. The plugs were replaced early (as were leads), all where in aged condition with a wide gap, but both banks were correct colour not burnt etc.


I am also not sure if there is a camshaft position sensor on both banks, but can find and confirm one on the left side which is not the bank with the error. See here.
If the right hand bank were stretched alone (as might be seen with lubrication starvation/limitation to the chain on that side) then it could be late and rattly but the camshaft timing appears normal to the ECU as it reads off the other bank sensor alone. This would lead to poor running at low revs with a chain bouncing around, but applying throttle would tighten it up and it might run smoothly. The sudden change is hard to rationalise but a broken guide/tensioner could have caused overnight failure.

More exploration to do.

Originally Posted by Julian B

The independent is not keen on the replace-parts-until-fault-resolves method, and their reputation is good. The issue with this Ford motor is that it is ultimately foreign to LR and although they agree that the absence of a timing mismatch code is odd, they have seen similar absence of codes in other cases for this motor.



The noise is subtle mostly when lifting off the gas in neutral. It runs roughish on idle but revs cleanly. I have done multiple hard resets to no avail. The plugs were replaced early (as were leads), all where in aged condition with a wide gap, but both banks were correct colour not burnt etc.


I am also not sure if there is a camshaft position sensor on both banks, but can find and confirm one on the left side which is not the bank with the error. See here.
If the right hand bank were stretched alone (as might be seen with lubrication starvation/limitation to the chain on that side) then it could be late and rattly but the camshaft timing appears normal to the ECU as it reads off the other bank sensor alone. This would lead to poor running at low revs with a chain bouncing around, but applying throttle would tighten it up and it might run smoothly. The sudden change is hard to rationalise but a broken guide/tensioner could have caused overnight failure.

More exploration to do.

I’d sell it at this stage!