VR6 random misfire

[Jim Bowen 1]

sometimes, very occasionally i get a misfire usually under load and i seem to notice it most after i've dropped speed and go to pull away/build up speed again.

 

feels like its not running on all cylinders for a breif moment, have to kinda dip clutch and give it some revs

 

is this likely to be coilpack, not sure when HT leads were last done either

[was8v 0]

3 things cause a missfire:

 

1) no spark

2) no fuel

3) no compression

 

Easiest to check is 1) so check your leads and coilpack. Unfortunatley these are difficult to check as issues may only occur under load (as you are experiencing). Try the obvious like spray a mist of water over the ht leads and coilpack in the dark and look for sparks. Look for any cracks in the coilpack (although I had one on my 1st VR6 that broke down internally giving the same symptoms as you).

 

Try and borrow a known good coilpack and ht leads or just buy new if they are original. I bought GSF leads (big mistake, buy some OEM from vagparts.com) and a used known good coilpack.

 

Pull your plugs and check for fouling that would kill a spark. My 1st VR6 would foul the plug on no6 with oil deposits as it was worn, and I had to change the plus every couple of 1000 miles - it still ran perfect the rest fo the time and made good power.

 

2) My 2nd VR6 was missfiring due a dodgy injector squirting too much fuel and dousing the spark - to check for this remove the upper inlet manifold and pull the injector rail - you can test by lining up 6 jars over the injectors. be careful not to get fuel everywhere! check the flow pattern if one is weird than likely to be the problem. Also check for fuel leaks along the length of the lines.

 

3) A compression test will reveal problems here.

[Jim Bowen 1]

i;m a bit late in getting back to this thread, but been looking around for misfire and found this, i must of forgotten i made it :cuckoo:

 

i have noticed sparks that come from the top of the coilpack where the lead joining it and the sparks jump to the metal thing sticking out of head above it.

 

not sure if its leads or coilpack, i might change both, no doubt these things cost over £100 each :sad: