Thread: Misfire driving me spare

Is it possible you have moved cyl 5 coilpack to a different spot while initially diagnosing ?, if so a rescan may show which cyl it is now at.
Did you use a new or known good one ?

I would expect if a vacuum leak was big enough to cause a misfire it would usually throw lean mixture related codes.

You can rule out transmission faults with an engine misfire

Originally Posted by BradC

For unmetered air leaks I've sprayed carby cleaner progressively over and around gaskets and seals. You'll hear the change if you hit the leak. I've also used ATF, butane and kero at various times depending on what I had available. All flammable of course.

I've not done it on a disco, but most common leaks I've encountered have been hardened injector seals. Since you've done the injectors I suppose that is unlikely.

If it is an unmetered air leak a smoke test should show it up pretty quickly also.

Haven't the gear fr smoke, but cannot trace a leak with carby cleaner.

Originally Posted by Eric SDV6SE

Weird that when revving in neutral the issue goes away. Engine is still under load, but not the transmission. Does it have issue at idle in neutral?

Assuming you have thr 6spd auto, it may well be an issue in the valve body in the transmission as in one of the line valves not closing properly, due to contamination or a dodgy solenoid, more pronounced at high loads due to increased fluid pressures....

Transmission was replaced and service 2 years ago- butter smooth shifting. I doubt this is the issue.

Originally Posted by discorevy

Is it possible you have moved cyl 5 coilpack to a different spot while initially diagnosing ?, if so a rescan may show which cyl it is now at.
Did you use a new or known good one ?

I would expect if a vacuum leak was big enough to cause a misfire it would usually throw lean mixture related codes.

You can rule out transmission faults with an engine misfire

Scan with every change I make. Misfire persists at number 5. I'm beginning to wonder about a computer signal issue as I can't see a leak here.

Tried replacing numerous sensors and blocking off EGR- no change.

Just a quick input here. When using a scanner Cylinder 5 is the fifth cylinder in the firing order not necessarily cylinder 5 on the engine.

The fifth cylinder in the firing order as per the manual is cylinder 3. So driver's side rear on a RHD.

Originally Posted by FisherX

Just a quick input here. When using a scanner Cylinder 5 is the fifth cylinder in the firing order not necessarily cylinder 5 on the engine.

The fifth cylinder in the firing order as per the manual is cylinder 3. So driver's side rear on a RHD.

I changed this coil also with no change, but good thought.
I might try to be a little systematic and swap out all of them and see what happens.

This is crushing me.

So changed all coils no difference.
Just got a crankshaft sensor pending error, though not illuminating CEL. Interesting. I wonder if this is the cause, or a symptom of a wider error.
Looks like parts shopping again.

Originally Posted by Julian B

So changed all coils no difference.
Just got a crankshaft sensor pending error, though not illuminating CEL. Interesting. I wonder if this is the cause, or a symptom of a wider error.
Looks like parts shopping again.

As mentioned way back in post #4. Check crank/cam sensors. I hope the crank sensor isn’t gearbox side on that engine

Originally Posted by DiscoJeffster

As mentioned way back in post #4. Check crank/cam sensors. I hope the crank sensor isn’t gearbox side on that engine

It is. Ha, at least the manual says it can be accessed without removing the engine.
Life wasn't meant to be easy.
Then daddy bought a discovery.

So, new crank position sensor installed. No change to the misfire/stuttering at idle and under load such as driving up hills.
This was a good thought but so far this and the cam sensors seem now excluded from contribution to the running condition.

Overall the only thing thus far that has made an improvement is artificially enriching the mixture with some ether sprayed down the throat when running. This implies a lean condition being corrected which would lean towards an air leak.

I am lost unless there are any further brainwaves.

Anyone?