VR6 Misfire when cold, now running on 5...

[sixpotter 0]

As above really, done a few searches but not too sure what it is.

 

Used to be somewhat lumpy from cold but was fine warm. Used to cut out randomly and always start up and run fine after.

Have slowly been replacing bits and have now changed:

 

Coilpack,

Plugs and oil,

Ignition switch

Cleaned immobiliser connections under dash and sprayed with wd40.

 

Just put up with it until this morning when I put my foot down and there was nothing, then power came back then it was running on 5 cylinders or less when I put it on the drive. Still runs just about and stinks of fuel.

 

Any ideas??

[Jon_vr6 1]

HT Leads what are they like?

[sixpotter 0]

They look OK but I they haven't been changed in my ownership (15,000 miles, 3 years) - Is it worth getting a set to try? If so is it genuine VW for these I think I've read somewhere are the best?

[sixpotter 0]

Found the OEM Beru ones for £68 delivered on VWspares... Should I give it a try or is there anything else to try thats free?

 

Luckily have my dads Transit to use while he's away but need to sort it before Weds and get it off his drive :(

[sixpotter 0]

Just ordered ecu and fuel pump relays (£45 for both) in for tomorrow, if not then its a set of leads. Fingers crossed. Already had a new fuel pump and filter.

[Kevin Bacon 5]

When did you last check the spark plugs?

[sixpotter 0]

When did you last check the spark plugs?

 

Replaced about 2-3 months 800 miles ago during its service..

[Kevin Bacon 5]

If none of them were oil fouled, then it's probably knackered HT leads as originally suggested, given that you've replaced the coilpack already.

[sixpotter 0]

They will be next on the list after the relays! Hoping it won''t come to that. Are the plugs easy to get to or is it engine covers off etc? I read about bore wear affecting a couple of cylinders which ones are these? I hope it isn't that or I'm doomed but should probably check. Car is on 119k.

[sixpotter 0]

Well, set of leads and two brand new relays later its still the same... Going to get a spare spark plug and make sure I haven't got a dud but they were only changed in July. If its not that then I'm breaking the bastard!

[sixpotter 0]

Pulled out the front left (from standing in front of the bonnet) spark plug and it was black with oil and broken down so swapped it for a new one and it runs again! What are my underlying issues with oiling plugs? Will the oiling break them down fast as they were only changed 2 months ago..

[fla 9]

Hmm oily plug is not good, but 1 and 6 usually foul up first. Means oil is getting past the piston...might be ok with a heavier grade of oil though.

[RW1 0]

Pulled out the front left (from standing in front of the bonnet) spark plug and it was black with oil and broken down so swapped it for a new one and it runs again! What are my underlying issues with oiling plugs? Will the oiling break them down fast as they were only changed 2 months ago..

Most likely cause is broken piston rings given the cylinder its from. Affects front left (No.6) and rear right (No.1) as fla says. Common problem with the VR6. Both cylinders go oval if the engine is allowed to run hotter.

 

A comparitive compression check across all six cylinders should confirm whether they have broken or not.

 

I keep the coolant mix at 40% additive/60% water and the engine oil temperature runs at 98'C knocking about upto 50mph and 104'C at 70mph for an outside air temp upto 21'C. The coolant temperatures are similar. Three open slat grille rather than two helps as does Slick 50. Run with 15w40 (Castrol Magnatec) oil and standard original NGK plugs.

 

.

[sixpotter 0]

Thanks for your advice chaps.

 

GSF gave me some Bosch super 4 thing (only bought one plug to test them) and the rest are Bosch supers with single tips which my local specialist put in during its service a couple of months back.

 

I remember my old mk2 8v needing some double tipped NGK's after reading up as when I put the specified ones in it drove like crap and they didn't match what the previous owner had put in.

 

So what are the 'magic' NGK's for a VR6 specified by VW/GSF or not? GSF said "you don't want them NGK's in a VW mate, they're only OK for little french cars"!!

 

Just wanted one that fitted on the day to text but now want the best considering the above symptoms.

 

Wheres the best place to order the oil and plugs too.

 

Much appreciated :-)

 

Getting the hump with the thing now, not sure I'll bother much more with this lump other than keeping some spare plugs and oil! If it dies I may consider binning the problematic oval bored 12v in favour of something more modern (and in keeping with the car of course) That is for another thread though..

[Kevin Bacon 5]

Start saving for a 24v mate, your 12v is on it's last legs I'm afraid :(

 

That said, a freshly built 12v feels and goes superb :D

[Critical_Mass 10]

That said, a freshly built 12v feels and goes superb :D

 

Oh yes!!! :D

 

Costs in the region of 2K for the rebuilt 12v engine plus what ever else you choose to do like new clutch and water pump or engine mounts, then there's labour to fit, unless of course you can do it yourself.

 

How much does the 24v engine cost Kev? is it a straight swap or do you have to change anything else to accomodate the engine?

[sixpotter 0]

Much as I love it and would love a rebuilt 12v I can't justify the cost, If I'm shelling out a bomb it almost has to go R32 for me.. Can probably get it all plumbed in myself with help and just get it set up by a pro.

[Timbo 0]

Fuel injectors?

[sixpotter 0]

Dead again! New plugs on order but the last one didn't last a week!

[sixpotter 0]

New set of NGK's later and its still at least a cylinder down.. pulling my hair out with it now! Think the only realistic thing is a complete transplant for a low mileage cheap vr be it 2.8 or 2.9 rather than pulling things apart.

[Critical_Mass 10]

New set of NGK's later and its still at least a cylinder down.. pulling my hair out with it now! Think the only realistic thing is a complete transplant for a low mileage cheap vr be it 2.8 or 2.9 rather than pulling things apart.

 

Seems a little extreme. Plus you could be swapping one set of problems for another. Is it always the same cylinder thats misfiring?

[RW1 0]

Have you done the compression test???

 

.

[sixpotter 0]

Compression test next weekend hopefully. Sounds like a 3cyl Daewoo Matiz! - Not sure which ones aren't firing if I'm honest though, how do I tell?

 

Have found a possible donor engine now but like you say that is extreme if its something minor.

[Critical_Mass 10]

Compression test next weekend hopefully. Sounds like a 3cyl Daewoo Matiz! - Not sure which ones aren't firing if I'm honest though, how do I tell?

 

Have found a possible donor engine now but like you say that is extreme if its something minor.

 

Have you got vagcom? where are you based mate?

[sixpotter 0]

I know someone with it who I can sort out a drink for for a reading but was under the impression not much shows up on it? I'm Based in Chelmsford, Essex.

On another note, all 6 plugs were a mess when I swapped them out today, not just 1 and 6.