FL2 SD4 misfire when warm…

Hi all, hope you’ve all had a great Christmas.

I’ve had my FL2 for nearly a year and it’s had a slight intermittent misfire since I got it which has been steadily getting worse. It’s a 2011 SD4 so it’s the auto. It only really happens when it’s up to running temperature then it will be really bad, even when I put it in N when at the lights it’s started doing it and it hesitates when pulling away.
I’ve done quite a bit to try and trace the cause but it is evading me… so far I’ve done this…
Gearbox flush (LR independent)
MAF replaced (fault on scan)
MAP cleaned
4 new injectors + coding and
Throttle body new
Codes deleted, rescanned after 7 days normal driving, no relevant codes.
ECUs reset

does anyone have any ideas?
Could it be a low pressure fuel pump?
Fuel filter?
High pressure pump?

(no clue if it’s relevant but it seems to have quite a vacuum in the tank when I fill it up. I did try driving with the cap off but thought better of it and put it back on although it didn’t seem to make a difference)

thanks for any help!

blackie781 said:

does anyone have any ideas?

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Have you changed the crank sensor?
Most misfire issues can be traced the crank sensor beginning to break down when it warms up.

It's unlikely to be the HP pump, and it doesn't have a LP pump.
The filter should be changed every 2 years, and only genuine (Purflux) filters should be used.

Hi Nodge, thanks for the reply.

No I haven’t changed the crank sensor but will look in to getting it done and see what happens. Would that not register a fault code on the diagnostic scanners?

I’m not sure when the fuel filter was last changed so I’ll get that done asap aswell just in case. It won’t hurt to get it done, prob just give it a service while I’m at it tbf.

I’ll post back with any results but is there anything else I could check while I’m there?

blackie781 said:

No I haven’t changed the crank sensor but will look in to getting it done and see what happens.

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It's an easy 10 minute job to replace. No need to take it to a garage.

blackie781 said:

Would that not register a fault code on the diagnostic scanners?

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Normally it doesn't, which is why it's often missed.

blackie781 said:

I’m not sure when the fuel filter was last changed so I’ll get that done asap aswell just in case. It won’t hurt to get it done, prob just give it a service while I’m at it tbf.

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It should be changed at 24 month intervals.
If it's not been done, then what other service items have been missed, like the Haldex fluid and filter, the transmission fluid, rear diff and PTU oils?
The Freelander 2 needs proper servicing on time, if seriously expensive failures are to be avoided.

I’ve got a crank sensor ordered should be here Friday.

Ah, that will be why it hasn’t shown a fault then!

it’s got a pretty good history with it, however I have overhauled the haldex and the rear diff and the haldex was absolutely howling! I’m surprised it hadn’t blown up! Gearbox was serviced a couple of months ago by a local LR independent. I presume the PTU is separate from the auto box and would therefore need serviced separately?

blackie781 said:

I’ve got a crank sensor ordered should be here Friday.

Ah, that will be why it hasn’t shown a fault then!

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Let us know if it solves the issue, but it is the common cause of misfiring.

blackie781 said:

I presume the PTU is separate from the auto box and would therefore need serviced separately?

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Yes, the PTU is separate, and needs a pump or syringe and thin hose to suck the oil out.
It's a silly design really, but is know to fail often, especially where Haldex servicing has been neglected.