I've been a member on FullFatRR.com for 11 years and have been wandering on and off the Sport forum for a while too as I've been trying to convince my wife to have a Sport.

In the last 12 months I've pretty much rebuilt my L322 from front to rear. Full story here if anyone is interested:

https://www.fullfatrr.com/forum/topic57991.html

Most recent works include replacing both the front and rear diffs, 4 wheel bearings, the bearing on the long front half shaft, and then replacing every single bush and balljoint between the front and rear bumpers on the car

Anyway... the reason for my post...

I've had an annoying misfire on the car when it's been cold for a while now and in a post on FullFatRR.com Gsxr1250dave suggested posting here as the 4.2 engine is common to the Sport and more heads are better then one Hopefully if we can find a solution it might benefit others too.

Anyway, here's my post from the L322 forum:

I’ve been chasing a misfire on my Range Rover when cold for a while now. It’s only noticeable when the car is cold and sitting idle. If you have any load on it at all it’s perfectly smooth. It’s also perfectly smooth once warm.

The above symptoms have also been confirmed by the IID tool monitoring real time misfires.

Plugs have all been replaced with genuine LR plugs, coils have all been replaced with genuine LR coils, MAF has been cleaned and the readings appear to be within spec. PCV Valve and hose to throttle body have both been replaced with genuine LR parts as well. The replacement PCV valve you can blow air through in both directions with no restrictions. I don’t have the old one any more to check it so am unsure if unrestricted flow in both directions is normal or not.

When smoke testing it I found a leak from an o-ring on the throttle body. I’ve replaced this and confirmed with another smoke test that this is now sealed.

When I had the car idling on the ramp the other night I could hear what sounded like an air leak. I can however confirm that it appears to just be air travelling through the PCV valve and pipe to the throttle body. To confirm this, I removed the pipe from the PCV Valve and stuck my finger over the end of it and as it sucked on my finger the hissing noise stopped.

Seeing as it sucked on my thumb with a decent amount of pressure I can rule out any leaks I think.

What really surprised me though is when my thumb was over the end of the PCV pipe, the misfire stopped and the car idled perfectly when it was cold. I got the IID tool out to confirm and the misfire counter was sitting at a stable 0 on all cylinders whilst my thumb was over the end of that pipe.

Removing my thumb and sticking it back on the PCV valve saw the return of the misfire and the misfire counter on diagnostics starting counting misfires again. Interestingly, the worst affected cylinder appears to be cylinder 1, the nearest to the PCV Valve.

The car has LPG on it as well as the flash lube valve saver fluid. I did wonder about damaged valve seats but am not sure that the symptoms would clear so perfectly when blanking off the PCV pipe if that was the case.

Has anyone got any suggestions? I’m wondering about blanking off the pipe from the PCV to the throttle body and fitting an oil catch can to cure it but would rather do it properly if I can.

I rigged up a home made smoke tester and found a leak on a rigid plastic pipe that pushes into a plastic collet with an o-ring underneath it and goes back to the brake booster.

LR don't list the o-ring in any of the catalogues. I did some Googling and found this kit referenced for a Jaguar.



I ordered it from Duckworths and it was around a tenner (can't remember if that was +VAT or not). I removed the pipe, teased the plastic collet out with a pick and found the o-ring in that kit to be a lovely snug fit. That pipe is now nicely secured and no longer leaking.

When listening to mine carefully it does sound like the revs are kinda surging so it makes perfect sense it's an air leak, it's just a case of finding it.

Land Rover list very few o-rings for parts on these engines so you end up having to change whole parts such as the oil filler neck and cap, or the entire dipstick to get the right size o-rings. Annoyingly, the dipstick tube is no longer available either.

Would be grateful for any pointers or suggestions.

Thanks,
David. 2002 Range Rover 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

Yeahh there was a jaguar post that had a similar problem. They basically just replaced the entire plastic pipe with a rubber one.

https://www.fullfatrr.com/forum/topic55398-90.html

I replaced that pipe last year on mine with a genuine LR pipe that was around £120.

If I put my thumb over the PCV end of that pipe it does create a vacuum and sucks quite hard on my thumb so I don't think there's a leak in that pipe unless it's the end that goes onto the PCV that's not sealing.

For sake of some 22mm rubber hose (might have some actually) I'll give it a go though.

Edit - Just seen you smoke tested yours too. What did you use to do it? I fashioned mine from a smoke pellet, an old paint tin and some rubber tube. It worked well enough to find the o-ring above but not sure it'll do much more.

David. 2002 Range Rover 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

I think the argument that was made was that its just badly designed pipe. I mean if you want to bypass if you can just install a catch can?

I wouldn't rule out air leaks on these cars. Bloody annoying.

I'm thinking of using black roof sealant (in desperation) to help with some of these air leaks.

1) What are your long term fuel trims?
2) What spark plug gap are you running? Try adjusting Spark plug #1 if you want. (gap smaller I think)

I’m fairly certain there’s an air leak somewhere but if I know where to start looking.

Here’s my long term fuel trims:



Long term trims fluctuating whilst idling:



Long and short term trims:



Long and short term trims at idle and with revs:



David. 2002 Range Rover 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

-3 is ok
-6 not great

Is it likely to be an air leak that’s causing the fuel trims to be off kilter?

I don’t really know a huge amount about fuel trims so I’ll start doing some reading.

Thanks Andy. 2002 Range Rover 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

I believe so.

Listen and feel around the joints.

Just a thought, if it’s been on LPG for a while, I wonder if I should reset the adaptions and see what the trims settle down to them.

I can hear air hissing through the PCV valve but can’t find a leak. It’s worse when cold, when it’s warmed up it doesn’t misfire.

Might see if our local specialist will smoke test it for me and see if anything pops up.

David. 2002 Range Rover 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

yah id clear your adaptations and run petrol for a good tank.

have you got sdd to see the full table?

also you're running rich, not lean which indicates the opposite of an air leak. most likely the lpg system playing it safe. i'd defo go with the above.

https://www.rrsport.co.uk/forum/topic56951.html

thats an example of when mine was lean as .

My biggest issue is whilst doing all my suspension work, the MOT has expired so the first trip I need to do is for the MOT where it'll be emissions tested. If something is wrong it'll end up failing the test on emissions I'd imagine. Especially as at idle that's when the misfire is noticeable. It's almost unnoticeable when hot so it might scrape through but I'd rather fix it then take a chance.

Part of me is tempted to change the MAF and both pre-cat lambda sensors but having spent between £3 and 4k on it in the last 6-8 weeks I'm reluctant to throw more at it incase it doesn't fix it.

Going to do another smoke test this evening and see what's visible.

David. 2002 Range Rover 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

I'd take it to MOT with the LPG on. Since they don't really test the CATs.

I wouldn't throw more money on it. I made that mistake.

For me when cold on petrol it used to misfire when I ran the LPG as my daily. But that sounds like a mismatch in trims I never managed to map out given am an amateur.

For me when I cleared the adaptations and stayed on petrol I had no issues outside my own problems. If your CATs are shot which can happen on LPG. MOT testers don't really test LPG the same way so might be worth cutting them out

I think it stands a chance of passing an MOT.
They test at 3000 rpm and when hot

If you think its running badly, disconnect the battery a day or 2 before the MOT to reset the trims

Done some more checking tonight.

The Air Flow Meter seems to follow the target. This was just after it had started to come off choke.

https://youtube.com/shorts/c7Gx0BC9128?feature=share

The oxygen sensor readings are dancing around too.

I’ve made a smoke tester tonight too.





Just need my torch wicks and some resistance wire to arrive to finish it off. Up

The plan is to remove the pipe from the NS valve cover to the air intake pipe and connect this to the air intake whilst blanking off the port on the valve cover.

The resistance wire will be wound around the wick and the wick soaked in baby oil or similar.

I’m then going to set the regulator on the airline to around 10PSI and connect the resistance wire to a 12v battery.

Once it starts to make smoke I’m going to connect the airline to the pot and hopefully watch for smoke coming out of something on the engine!!

That’s the plan anyway! 2002 Range Rover 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior