8v that has decided to mis fire!

[gti69]

Hello,

I have an 8v GTi that has just started to mis fire, the car has had a new dizzy cap,  rotor arm and spark plugs within the last couple of months and has been faultless, until a couple of days ago

It has started to mis fire, but it only seems to do it when you just rest your foot on the fun pedal, when you press the pedal down a little further it seems to dissapear. I was thinking it might be the leads but with my limited knowledge i would appreciate a little help.

Thanks in advance

[gti69]

By the way it's a 1991 H reg! I forgot to mention this, not sure if it will help.

[Krankev]

i own a 89 8v gti which is also misfireing the only thing i have did was to try ?20 worth of shell optimax any help would be greatly apreciated.

[gti69]

Funnily enough, i have just recently used optimax and then the mis fire started. I had previously been using Super unleaded. I think i may try going back to that and see if it cures it.

Could it just be a coincidence?! Up until that point the car ran fine, i have heard nothing but good about Optimax though.

If anyone could shed some light on this it would be greatly appreciated.

Has anyone else had problems with using Optimax?

[midlander]

when i worked in a garage we fuond that cars which had just started using the then new unleaded fuels suffered a build up of silicon in the spark plugs (yellow staining appearing between metal and porcelin near the bottom) the plug would then fail...

again this was sometimes cured by heavy throttle or light throttle..

odd symptom but new plugs always cured it

[Thom89]

Plug leads + damp weather = your symptoms
Have a look under your bonnet in the dark, your looking for anything that may be sparking/arcing... leads, coil, dizzy etc only dont touch! they may bite! also re-check your new parts, if they're not OE, they may be crap!
Tom

[bomp]

Mine was firing on three pistons on Friday, and didn't start at all Saturday. (guess I flooded the carb)

So spent Sunday morning (20 Mins) finding the guilty plug. On closer inspection of the HT cap, there was a tiny part missing in the centre of the cap, it would probably be cylindrical in shape that fits over the thread of the spark plug.  Anyways, I wrapped silver paper over the thread of the plug and after a couple of go's of starting her up, she's as good as gold now.

What I can't understand for the life of me is, where the bloody hell did that tiny part go.

It's fine as a temp repair, at least I know what it is now.

[rubjonny]

Don't mess about, just buy a new set:
http://www.vwspares.co.uk/product_info.php?products_id=173

For £16+VAT it would be rude not to