Random misfire / rough running

[antgel]

Hi all,

My 8v recently started to develop an intermittent problem with what feels like a misfire.  It doesn't seem to matter whether it's cold or hot, I started it last night and it was kangarooing really violently, then today it was as good as gold when I drove it into the garage.  When it has done this, I could swear there has been a smell of fuel, which made me think no spark on one or more cylinders.  Power is well down when it's like this.  Cap, rotor, plugs and leads are all pretty new.

Originally when it started happening, I would pull over and lift the bonnet to see if I could see anything wrong, but it all looked fine.  One time, I thought pushing the ignition lead plugs more tightly onto the dizzy in case there was a loose connection made a difference, but now I think that was a red herring, as it hasn't worked since.
Other times, it has corrected itself - one time it was kangarooing so badly it was frightening, then I could swear the vibration shaked something back into place, as it started to run fine with no assistance.

I'm going to check the hall sensor and other ignition components with a multimeter, and have a look inside the cap, but what really worries me is the intermittent nature of the fault.  I would have thought if a component fails then it doesn't get better, but who knows.  I wouldn't be surprised if some of the wiring was baked after 133000 miles - e.g. the coolant level sensor wiring is faulty - I know this as I've changed the sensor and the light's still on.

I know I've been a bit vague but if anyone has any (informed) ideas I'd like to hear them.

Antony

[Mew]

With the hall sensor, although it may work when you stick a multimeter on it, it was the connection that was dodgy in my case. So don't rule it out if it seems to check out ok!

If it's definitely not the leads/plugs/cap etc then it may be the coil?

[antgel]

With the hall sensor, although it may work when you stick a multimeter on it, it was the connection that was dodgy in my case. So don't rule it out if it seems to check out ok!

If it's definitely not the leads/plugs/cap etc then it may be the coil?

Thanks for replying, what took you so long?

As I already said, I wouldn't be surprised if it is the wiring, but I hope not.  Indeed, I will be checking the coil as part of my multimeter "fun".  Intermittent faults are easily the worst, grr.

[Mew]

I suppose another thing could be your plugs, even if they have been replaced

Has the car been set up properly? timing/co reading etc like this (if it's a digifant):

http://www.golfgtiforum.co.uk/index.php?topic=33253.0

If it isn't running properly then the plugs could of had it, and it may also explain the petrol smell.

[antgel]

Hmm, a quick look shows the red lead on the dizzy multiplug was frayed.  A quick tug, and it snapped.  I'm going to crimp it before I do anything else - it's got to be suspect number one at this point.  Certainly, the car doesn't start with it disconnected.

It's quick to do, which is a nice bonus.

[antgel]

No luck.  Checked the switch unit and it failed the 2V for a couple of seconds test in Haynes (step 7 I think).  Checked the coil - primary windings only 0.1ohm.  Next step - new coil...