Yet another Vr6 Missfire. UPDATE: missing on 1 and 6

[was8v 0]

Apologies for the short sentances but I'm at my wit's end with this.

 

My VR is not firing on cylinder 1 - this only seems to happen when warmed up.

 

Removed plugs, the plug from cylinder 1 is the only one wet with petrol.

 

Swapped whole HT lead (new leads 4 months ago) with another and still plug 1 is wet.

 

swap plug with a new one, still wet and missing.

 

connect spare plug to lead on cylinder 1 and start car - runs the same (missing on cylinder 1 obviously) and plug connected to lead 1 is sparking away happily.

 

Hook up to VAG com, no fault codes.

 

Wait till dark and spray coilpack and lead with water and see no sign of arcing

 

 

 

 

any ideas what is wrong?!

 

 

 

 

 

I suspect coilpack - any other way of checking this apart from the water spray? Given that I get spark when the plug is out and there is no sign of arcing I dont really want to buy another (£125).

 

Any signs of a lack of compression on cylinder 1 to look for? Engine fouled up plug 1 over 3k miles on 10w40 oil, but still pulls like a train and ran great until this missfire.

 

If the O2 sensor was out, I'd expect too much or too little fuel across all 6? I hear I have more chance of winning the lottery than a Vr6 injector failing.

[dr_mat 0]

You can get spark testers in Halfrauds (or in a reputable car parts place). Just plug it on the top of the plug and then plug the lead into *it*. It'll flash each time you get spark.

This will confirm that the spark is arcing across the plug *when fitted*. (Don't forget the current has to earth to the cylinder head and back to the battery.)

 

You could also have a dodgy injector if it's flooding the cylinder. I've heard of one or two others, but you're right it's rare.

[Supercharged 2]

I don't think those spark testers work with VW's as they need plugs with the clips screwed on the top and the leads to match - the VR maybe different with it's smaller plugs tho??

[was8v 0]

will do, have been advised to swapo leads on the coil pack to see if it changes anything:

 

he coil packs on vr6 engines have got three coils. What happens is that each plug fires twice each cycle. Once on exhaust and once when it fires. Its called a redundant spark or something. So if it was the coil pack it would most likely miss on two cylinders not just the one. What you could try doing is swapping the lead on the coil pack with its twin. when looking at the coil pack you should see they are connected in three pairs. just swap top and bottom over.

[was8v 0]

What you could try doing is swapping the lead on the coil pack with its twin. when looking at the coil pack you should see they are connected in three pairs

 

done this, same result, miss on one, however.....

 

So if it was the coil pack it would most likely miss on two cylinders not just the one.

 

UPDATE: Out of curiosity when you said this I pulled no.6 plug (no.1's twin) and this was covered in petrol too, so must be missing on that cylinder too.

 

Does this point to the coilpack then?

 

Anything else I can try?

[dr_mat 0]

Not really. As stated, coil pack does two cylinders at a turn, so if the CP is gone, you tend to lose two cylinders.

1 and 6 don't share the same coil in the CP though, so don't think this can be the CP.

How much oil does the car use?

[double-6s 0]

Feked no.1 bore?? :(

[was8v 0]

Not really. As stated, coil pack does two cylinders at a turn, so if the CP is gone, you tend to lose two cylinders.

1 and 6 don't share the same coil in the CP though, so don't think this can be the CP.

How much oil does the car use?

 

500ml over 2k miles ish? (there is no blue smoke, except a slight puff on overrun)

 

 

 

Which cylinders share the same coils in a coilpack then?

[dr_mat 0]

Not really. As stated, coil pack does two cylinders at a turn, so if the CP is gone, you tend to lose two cylinders.

1 and 6 don't share the same coil in the CP though, so don't think this can be the CP.

How much oil does the car use?

 

500ml over 2k miles ish? (there is no blue smoke, except a slight puff on overrun)

 

 

 

Which cylinders share the same coils in a coilpack then?

 

Can't remember. Look at the coil pack - note that the HT leads that are stacked vertically come from the same coil (there's three, obviously).

 

500ml oil over 2k miles is not a problem at all. Sounds more likely you've got spark or fuelling issues based on that.

[was8v 0]

Got another coilpack and it's running fine, thanks to all for the help.

 

Was no evidence whatsover of damage or leakage from the coilpack, looked fine from the outside.

 

Cylinders 1 and 6 definatly share a coil in the pack, 3 and 4, 5 and 2.

 

:)