VR6 Constant misfire - Ideas welcomed...:(

[clubsport78 0]

Hi All,

 

I have developed a rather pronounced and constant misfire on my VR6. Driving along on Sunday at a steady pace (30mph) and went to give it a bit more gas and hey presto, it had turned into a lawn mower! It is a constant misfire, as soon as you start it up it is there. It is driveable, but does not sound well. The car is a late '93 (L) with 127000 miles and I believe is on the original chains.

 

I am not too sure what it is... I have a receipt for all new plugs and leads from the previous owner 10000 miles (2years) ago so I am doubtful that they are going to be the issue (?). I am just waiting for my lead tool (big thanks to Zerocool :clap: ) to turn up so I can whip the plugs out and have a look to see what they look like.

 

I understand that the coilpack could be another culprit. It looks in good condition but have not tried spraying it with water yet to test for any arcing. When it is on and I have my head under the bonnet it sounds like there is a misfire on cylinder 5, but it is difficult to tell as it is also at the end close to the coil pack.

 

There is no real smoke that I can see and all the levels look OK. It has been smelling a bit if petrol under the bonnet though, although I had put that down to a jubilee clip on one of the two rubber feed pipes which I tightened up a couple of week ago after I noticed it was dripping slightly... It was also slightly lumpy on tickover for a while (the revs were not surging at all though).

 

In regards to diagnostics, I have the later "hex" (?) type connector by the gear stick and would like to get it on VAG-COM. I have downloaded a free VCDS (ver. 805) program from Rosstech to my laptop and was going to buy a lead off of e-bay. Is that all I need and will the Rosstech program work then or do I have to buy one of their expensive leads?

 

Could it be something more serious such as a bent or snapped valve or slipped belt ??! :censored:

 

As you can probably tell, I am not exactly mechanic of the year, but any advice would be appreciatted and also any advice on what checks to try and any order to do them in :D

 

Cheers.

[CorradoVR6-Turbo 0]

its more than likly the coilpack or leads to be fair,under load will show up weak ignition parts,can you get the missfire on at idle?

[clubsport78 0]

Yep it is misfiring at idle and under load. It is a fairly constant rhythm...

 

Thanks.

[CorradoVR6-Turbo 0]

Yep it is misfiring at idle and under load. It is a fairly constant rhythm...

 

Thanks.

 

 

when its missing and you have your head under the bonnet can you see/hear clicking/arcing?

[clubsport78 0]

There is like a double pop/click sound that seems to be coming from the right rear side of the engine. Can't see any actual arcing as such.

[CorradoVR6-Turbo 0]

There is like a double pop/click sound that seems to be coming from the right rear side of the engine. Can't see any actual arcing as such.

 

 

sound like coilpack,fire the car up and get the missfire to start...and while its nice and dark outside have another look....you should be able to see the arcing either around the coilpack or the leads..get a good look down the hole of the lead to the plug.

[clubsport78 0]

Cheers James, will try that tomorrow night. Hoping that is the issue as it is a fairly easy fix I suppose. That would make sense...New one from VW is £180 though so may have to take the Beru route!? Thanks.

[CorradoVR6-Turbo 0]

Cheers James, will try that tomorrow night. Hoping that is the issue as it is a fairly easy fix I suppose. That would make sense...New one from VW is £180 though so may have to take the Beru route!? Thanks.

 

Beru is VW own brand and i just bought one from Euro for 114.00 quid but make sure its not a lead first bud. :wink:

[clubsport78 0]

Yep will do! That would be an expensive mistake if it was just the lead/plug. Good to know the Beru unit should be OK as I had read a few people slating them? Thanks for the advice :salute:

[Neil VR6 0]

As you’re fairly local to me and hence JMR in Littlehampton West Sussex I suggest you get the car down there for a proper diagnosis. I had a similar problem with mine and ended up having the car off the road because I didn’t take it straight down there in the first place. Misfires can be tricky to diagnose and can often be attributed to a number of factors which compound one another.

 

My misfire/rough running was a combination of a fubar’d distributor, shoddy GSF leads, old plugs and a very tired MAF sensor.