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[D]

Getting an occasional misfire, more so on LPG which is to be expected I guess. p0300 is the code. Cylinder 4. Now I was going to change the plugs, but do I need to buy a coil pack as well just in case? What sort of price is a coil pack? Would one from a breaker be good enough?

Anything else I need to consider? Dont want to take everything apart, put it back and find that the problem is still there.

[tunnie]

Start with fresh plugs, then go from there 

[RobG]

Getting an occasional misfire, more so on LPG which is to be expected I guess. p0300 is the code. Cylinder 4. Now I was going to change the plugs, but do I need to buy a coil pack as well just in case? What sort of price is a coil pack? Would one from a breaker be good enough?

Anything else I need to consider? Dont want to take everything apart, put it back and find that the problem is still there.

Before changing plugs swapout #4 with one of the others, see what code you get then

[feeutfo]

How old is the coil PAC D?

While I agree with the comments above, and trying to keep costs to a minimum... my experience with LPG suggests coil pacs are more reliable from new compared to one with say 80k on them. (where as petrol only cars will go on to 120k with a cp normally)

The pas side is also more likely to suffer water leaks from the scuttle. Given the recent weather there may be evidence of water/rust/lime scale along with the usual oil from failed cam cover leaks.

It's up to you obviously, without knowing the cars history with cam cover gaskets and mileage, it's difficult to say. Doing the job once might involve re doing cam cover gaskets as well, re seal scuttle, new plugs and cp.... Might just be plugs are are over due.
Might be necessary to go in there again once the cause is found. Also check the windscreen seal to scuttle is sound.

Sorry to be vague but it depends on the history and miles, and obviously what the cause is.

[D]

Sorry, I should have stated the obvious details in my opening post. 2003 3.2, one owner before me, its done 25k so far (about 4k with me). Serviced yearly with cambelt changes as prescribed. Cant see any evidence of a spark plug change (ie bills etc), but as the previous owner was the owner of a Vx dealership, I suspect cost wasnt an issue and things were changed as per Vx advice. Cam cover gaskets, Ill pass, I dont know if they have been changed.

I cant see any leaks or rust or lime scale as far as I can see. Obviously I havent disassembled anything due to my complete lack of mechanical skills.

Now that it has been LPG'd I am even more wary of doing things myself lest I muck anything LPG related up. I was going to get the chap who LPGd it to change the plugs at the 1000 mile check up. I did get the thermostat changed, with hindsight I should have probably changed the plugs at the same time for the minimal extra outlay. What I dont want to do is change plugs and then realise it was a coil problem. I would rather just change anything that needs to be changed at one go (reliability is key here). Plus if I need to use TC, then I will need to order everything from AndyC. If I just order the plugs and then need a coil pack, that would mean putting everything back together, then waiting till the part got to me, then back to LPG bloke for a refit.

[Kevin Wood]

Spark plugs are an 80K change on these so unlikely they've been done. I would say that should be first port of call, checking for oil or water in the plug wells, and any signs of obvious degradation of the coil packs.

[feeutfo]

... might be tempted to do the lot and be done with it then?

Coil PAC needs to come out to see the above mentioned rust/oil or whatever in the plug wells.

On the other hand it may just be a loose plug. They are known to come loose.

If it was mine though, I'd change the plugs and see what issues are discovered in the plug wells while doing the job. But appreciate that may not suit your good self.


End of the day, there's no chriystal ball for knowing the fault until the coil PAC comes out.

[Lazydocker]

It is of an age , although mileage is very low, that CP start to fail As I have already suggested to both yourself and Toby

As I understand it, the miss fire is very slight and only apparent on LPG, so it's likely to be HT related (I know Toby swapped the LPG injectors over to check it wasn't a faulty injector) and I would suggest, like Kevin, that the plugs will never have been changed

I think I would probably change the plugs and see what happens, although I don't have to take labour costs into consideration. The CP has to be removed to change the plugs so there would be no additional labour charge to change it at the same time, just the cost of the CP. Make sure it's either Genuine or good quality Bosch only though... Don't be tempted by an eBay cheapie

One thing you could easily check, even with very limited mechanical skills, is check the foam under the scuttle for moisture. If it's sopping wet then it's a good pointer that the CP may be fried

[JamesV6CDX]

It's probably due a good routine breather clean, too

[feeutfo]

Cp ain't cheap from a dealer. Even in tc.

Eg all parts direct supplied a genuine Bosch for £71 iirc. So it's worth looking around and haggling with local factors... If you need one.

[D]

Thanks chaps. Vx coil pack is £86 on TC, not bad at all.

What about the HT leads? Do they tend to perish at this sort of age? I have heard they are quite expensive?

[RobG]

No leads with a coilpack

[feeutfo]

+vat?

http://www.omegaowners.com/forum/index.php?topic=90670.0

[D]

No leads with a coilpack

Shows you what I do and dont know!

Maybe I should just stick to what I am good at!