Help me with my misfiring problem!

[seventhirteen]

I didnt know if to put this in Mk1 or mk2 because I have a mk1 shell with a 2L block and mk2 16v head but anyway I choose to put it here cause this seems to be the more active board.

So im having a misfiring problem which started about 3 weeks ago. Misfiring under heavy load only. At night I could see arching from the ignition leads to the inlet runners so automactically I assumed it was the leads. Got a set of new ones and a set of second hand, but pretty much new spark plugs and yeh, fixed it for about a week till the misfiring progressivly came back.

Gave the original owner a call and he said the car has a weak coil so I changed that with also a second hand coil. Didnt fix anything.

Decided to do abit of my own investigating and proceeded to a compression test but before I got there I saw the "newish" spark plugs had gone all black. So I thought it was a too rich a mixture problem. Turned down the mixture screw to lean out the mixture a bit and it worked for about 10 minutes till now the misfiring has pretty much gotten to its worst point.

So before I go any further into investigating this, I was wondering if anyone could give me any advice they can have or any suggestions. It would be greatly appreciated. Thank you.

[h100vw]

What kind of fuel injection and ignition system are you running?

Is the spark still breaking out of the leads? Could be the plugs are gapped too big causing the break down? What's the state of the cap and rotor?

Gavin

[mikinoz]

Is it on carbs or injection?

If injected it could be a Coolant Temperature Sensor sending too much fuel? The screw is an idle screw not a mixture screw.

Is this car known to the forum, let us know.

[seventhirteen]

Car runs k-jetronic. I turned the mixture screw. Dont know if anyone knows the car but its a green mk1 golf lowered on custom coilovers with mk1 cab rims. Its currently in hornsb, nsw.

And yes, from the new leads, arching is still going from the leads to the inlet runners. I even see arching from the coil lead to some random spot too. If I were to get new spark plugs could someone put me in the right direction to getting exactly the right ones?

[mikinoz]

Accept my apologies, as I was assuming electronic injection.

[Valver.]

The plugs will be black because you have a misfire, not necessarily because you have a mixture problem! When the fuel hits them and there is no combustion, they'll of course foul up whether or not the mixture is too rich, so don't go randomly playing with the mixture screw, otherwise you're likely to wind up with bigger problems

Have you got a good spark tester (i.e. not one with a light, but one that has an adjustable gap and has good visibility)? If so, see what the spark looks like and also run a compression test and then post results.

There are a bunch of common 16v misfire causes, but there's no point going through them without first checking the basics.