VR6 misfiring problem - all cylinders firing, but down on power

[Reverend Frog 10]

Searched the forum to no real avail!

 

My VR6 has started running badly as of yesterday:

 

• Down on power
  
• slightly lumpy idle, like you can feel the car sort of jump slightly every couple of seconds.
  
• lumpy sound and ragged response when throttle floored, not smooth
  

 

Today I checked all the cylinders by pulling the HT leads off one by one. That makes the idle even worse for each, but this suggests that the issue is not as simple as a total misfire on one cylinder.

 

Another issue that I've noticed in recent times is oil smoke from the exhaust, suggesting valve stem seals are going. Is it likely that some of the spark plugs are getting oily and this is what's causing the issue?

 

To further complicate things, since this problem reared its head yesterday the oil burning seems to have stopped!

 

Only other thought is the coil pack - hopefully not though.

 

I know I could just go and check the spark plugs but haven't got much of an opportunity to work on the car, and it needs serviced anyway.

 

cheers

[robrado974 1]

So the car is still lumpy after the leads have been refitted and tight ? . To check the coil pack , start the car in the dark . If you see a firework display from the pack this will explain the lumpy running .

[Reverend Frog 10]

Cheers for the advice.

 

Started it in the dark there, didn't see any pyrotechnics from the coil pack. I suspect oily spark plugs.

[easypops 8]

Try spraying the coil with a mist of water while it's running

[Reverend Frog 10]

Try spraying the coil with a mist of water while it's running

 

And if we get fireworks, that means the coil pack is goosed? and that's my problem?

[easypops 8]

Yes, happened to me, only found it bad in the rain.......went through a big puddle and the car started running terrible, popped the bonnet and the coil pack was doing the blue spark dance :)

[Stonejag 10]

It does sound like the coilpack. VR6s are wasted-spark so there are three coils in the pack which have two outputs each. When one output goes bad it'll start occasionally missing on one cylinder, but then when the whole coil drops out it'll run like a dog (a geriatric dog, with three legs, crawling uphill through treacle) and be undriveably slow. Don't leave it that late or you'll be going home on a flatbed.

 

The cause is that the plastic housing tends to crack which allows water to seep into the gaps and short the spark to the engine block instead of passing it up the HT lead. It is possible to seal up any visible cracks with epoxy (Araldite will do the trick) but they inevitably fail again - just another bit of poor design. That said they are still available from decent parts outlets - GSF do two types priced around £60ish or £90ish which are pretty much identical. I have a couple of spares if you want a cheap one to try out.

 

Stone

[Reverend Frog 10]

It does sound like the coilpack. VR6s are wasted-spark so there are three coils in the pack which have two outputs each. When one output goes bad it'll start occasionally missing on one cylinder, but then when the whole coil drops out it'll run like a dog (a geriatric dog, with three legs, crawling uphill through treacle) and be undriveably slow. Don't leave it that late or you'll be going home on a flatbed.

 

The cause is that the plastic housing tends to crack which allows water to seep into the gaps and short the spark to the engine block instead of passing it up the HT lead. It is possible to seal up any visible cracks with epoxy (Araldite will do the trick) but they inevitably fail again - just another bit of poor design. That said they are still available from decent parts outlets - GSF do two types priced around £60ish or £90ish which are pretty much identical. I have a couple of spares if you want a cheap one to try out.

 

Stone

 

Ha, thanks for that very eloquent explanation!

 

Car is going in for a service next Wednesday...how much would you be asking for one of your coil packs?

[swiftkid 1]

Obviously check the above but definitely worth taking out spark plugs, checking them and cleaning them up if necessary. Have you unplugged MAF when warm? If the engine note changes and splutters you can tick that off the list as thats working.

[Reverend Frog 10]

Obviously check the above but definitely worth taking out spark plugs, checking them and cleaning them up if necessary. Have you unplugged MAF when warm? If the engine note changes and splutters you can tick that off the list as thats working.

 

It's just got a new MAF so that shouldn't be the issue. I will check all of the above. I still suspect the spark plugs though too...no idea when they were last changed

[Jim 2]

VW Spares (http://www.vwspares.co.uk) list a coil pack at £166.20 :)

[Stonejag 10]

Ha, thanks for that very eloquent explanation!

 

Car is going in for a service next Wednesday...how much would you be asking for one of your coil packs?

£20 posted should do it, let me have your address by PM and we can sort the money out afterwards :)

[Reverend Frog 10]

On a drive this morning the car suddenly started running properly again. Does this make the problem seem any clearer? I guess it rules out the spark plugs being filthy as it's obviously an electrical problem and not something physical like that. Could still be coil pack, but I also suspect the ISV, which has never worked properly (and I have cleaned it within the last six months)

 

Damned complicated cars! Was so much more straightforward with my old carb'd Scirocco

[easypops 8]

Check all your leads are seated in the plugs correctly

[Stonejag 10]

Did you lube the ISV after cleaning it? Common mistake is to just blast it through with carb cleaner, which removes the oil and makes them stick. Try some WD40.

 

Stone