Hi guys. I just got home in my GF's 1972 1600 bug in quite distressing circumstances.
The engine has been a little off lately as it has been backfiring in (or should I say outside) one cylinder when under load such as going up hill.
I wasn't sure what the cause of this was and was going to get a service in a week in school holidays (yes I'm a teacher).

Tonight after the car had been sitting for two and a half hours we got in and after some difficulty started it. There were clear problems as we could hear that two cylinders were firing, but the other two weren't and the fuel was detonating late (backfiring). It's only a ten minute drive home and we didn't want to get the car towed without giving it a chance so we saw if we could get home. Basically the situation didn't improve but we did get home on just two cylinders and alot of farting.

There are a couple of possible causes that my dad and i came up with.
The fuel filter over the last 8 months or so has indicated that we've had some bad fuel go through as it's had to be changed (brown not black residue), but it seems like fuel is getting through so:
I'd noticed that the stock oil based air filter for the carbie seems to be leaking a bit and this has had me nervous. Oily residue has been leaking directly down onto the fuel lines and landing on the distributer. This may be corroding the fuel lines, but as I said fuel doesn't seem to be the problem. It may however be causing some carbon buildup in the distributer and shorting it?
The other possibility is just that one of the clips is not properly fixed to one or two of the spark plugs?

Has anyone heard of this before or anything similar?

backfiring or missing ??

sounds electrical, check your spark plugs,leads, coil condensor.

When was the motor last serviced, I mean tappets,timing,filters oil etc?

oil filter was a couple of months ago but not sure about the rest because it's not my car. It's been taken to the one guy on the coast for a while because of loyalty but we think we might have to start going somewhere more local. Volkspower is really close (burwood Vic) does anyone recommend them?

volkspower has been arounf for a LONG time, my father bought parts for his beetle from them when he was 18, so i would have to say that they are probably pretty good to have lasted so long with a decent reputation.

Volkspower are good, have been there a few times, I believe they are forum sponsors.

Currently use Volkscare in Bayswater, but this might be a bit far for you

I have been using them for about 7 years and have had what I would call good service and decent prices.

thanks for the feedback guys.
It's a bit weird though because I took the beetle for a tentative wander today and couldn't feel anything really wrong like last night.
We're going to give volkspower a go on this one and then we'll see from there on in.
Thanks again:thumb

it wont be a fuel problem. my money are on closed up points, a cracked dizzy cap, crap leads or a cracked rotor button. could also have been condensation in the dizzy cap.

remember: 9 out of 10 carby problems are NOT the carby.

I agree with Secoh

if it is intermittant it will almost certainly be points leads cap etc.
Some thing is breaking down and causing a missfire.

Certaily for the $25 - $150 do a basic tupe up (depends if you do it your self or pay some one)

But certainlt change cap rotor condenser points and set valves

Well we took a gamble on the weekend and it ended with the car on the side of the road. In the week following the first incedent the car ran fine during the day, if a little underpowered, but the problems came out at night. This led me to a somewhat uneducated conclusion that condensation may somehow be getting into the distributer when it was wet and cold at night and this was shorting the firing sequence a bit.

So with this theory under our belts on Sunday we decided to drive her down to visit my dad (who has a fair bit of vw experience) and if that failed we'd see our usual mechanic (volkspower were a bit steep for our meagre budget). We left late morning with the hope that it would be drier and less traffic. Anyway the trip was fine for about 1/2 an hour until we got to the Westgate and she started playing up (I had visions of going backwards down the bridge while people were swerving either way). She was then fine for most of the trip to Geelong, but every now and then she would miss a whole sequence (sorry I repeat I'm relatively uneducated) so for a split second there'd be no power and then it'd come back on, which created a bit of a lurch.

I was worried about damage this might have been causing, but my copilot (the owner) said she just wanted the car in Geelong so I had my orders.
Anyway we did get into Geelong and she seemed to be running ok until we went around a roundabout and about 20 meters later power went in an instant accompanied by a wierd light rattling sound. The car lost a valve into the piston chamber a couple of years ago so I'm pretty tense about wierd noises so i turned her off and pulled over.

So there she remains for now until I get her to the mechanic (tomorrow). I got my dad to come and have a look and a listen, eeeewwww it still makes me cringe to think of the sound, like a spray can but less regular. We checked over the obvious parts of the engine (leads, distributer etc.) but couldn't cancel them out because we didn't have mush in the way of tools, but there was nothing obvious.

So amateur diagnosis:
(mine): I think there could be a small foreign object in the piston chamber (but then again I'm paranoid).
(dad's): He thinks it may be pinging, which would follow on if the whole problem has been due to timing/firing/ignition.

The car will start and run kindo ok, but I don't want to chance something messing up the engine so we're going to get it towed (properly) to the mechanic.

Sorry for the long-winded update.

progress moved to thread titled "crisis point"