Mysterious vanishing misfire

[Watty]

I've not used my C4 much lately (been driving a Freelander 2 for work) and gave it a short run last weekend for the first time in 3 weeks... Went through a lot of water and developed a really bad misfire on right hand cylinder bank (sounded like Del-Boys van!) Engine check light flashed and then went out when I backed off throttle. Left the car for about an hour and it worked fine (no misfire).

Then today, started fine, got about 5 miles then put foot down to overtake and back came my misfire and flashing check light. Light went out when I backed off... Tried again and same happened... Third time Engine check light stopped flashing, but stayed on. Switched off for 10 minutes and then restarted - no misfire, but light still on.

Tried accelerating, no problem - engine sounds great, got brave and went to the rev. limiter - still no misfire and been fine for about 30-40 miles since (but light still on)...

Booked into OPC on Tuesday, but if they are going to charge me hundreds just for clearing the fault memory I'll take it to an indie!

Any ideas?

Thanks in advance,

Watty

 

[Bull996]

I am guessing a coil pack. Covered under warranty or about £150 all in I think.I had exactly the same symptoms.

 

[Black80XSA]

Certainly sounds like a coil pack - they crack with age and the heat from the exhausts - damp/wet weather highlights their disintegration - eurocarparts sell them for about £40 each incl vat

 

[Watty]

Thanks guys,

Think I might try that myself (I think you may be right as I now remember having identical symptoms years ago on my Trooper - and fixing it myself) - trouble is I need it to misfire again so I can find out which one! OPC will charge me more than £40:00 before they've even opened the engine cover, and at that price it's not the end of the World if it doesn't cure it.

BMW (Brave Man without Warranty!) - a very long saga that I won't bore with here!

Excuse my ignorance here, but is the 3.4 engine twin spark? And, if so, I presume there is just one coil pack for the two plugs? I also suspect that the coil pack won't be quite as accessible as it was in my Trooper - where it was sitting up there on top of the engine for all to see (and spanners to reach without skinning knuckles!)

Just need to get someone to clear the fault memory after and get rid of my orange light!

 

[Richard_Hamilton]

There is one coil pack per cylinder. See this thread, which also has some instructions:

http://www.porscheclubgbforum.com/tm.asp?m=232376&mpage=1&key=coil%2Cpack&#232376

 

[JColbourne]

Ian,

My experience (see my topic Mis-fire Problem) is that the coil packs can exhibit varying levels of damage depending on their position on the engine. My advice would be to let an indie take a good look. You might find it's worth changing them all rather than doing one and finding another/more fail shortly afterwards, bearing in mind we're approaching winter. At least you'll have the confidence that they're all at a consistent state.

I'd be interested to see if your car is displaying the same problems as in my topic.

Good luck, hope the fix is a simple one.

Rgds


John

 

[Paul Fraser]

You might want to invest in a code reader. It helped me diagnose a coil pack problem and I subsequently replaced all of them. I've also used it two or three other times.
If you do it yourself, do the right hand side first and lie with your feet pointing towards the other side of the car -- I know this sounds daft but it took me ages to work out the best way to do it. You'll need offset spanners for the cover (offset? - ones that are sunken at one end) and a hex spanner for the coil packs. Ages to get off but quick to put the new ones in. £24.50 + VAT from ECP.
PS It might help you to mention where in the country you are: you may be beside someone with a code reader.

 

[Watty]

Thanks everyone,

Don't need to use the car at the moment, as I have a Land Rover from work for the next couple of weeks (and with Chrimbo coming up, might put it off until January when it will need a service and MOT anyway).

Will let you know what the outcome is when I get around to sorting it...