Miss firing!

I'm having problems with my MK1 GTi miss firing. It runs fine and then suddenly it starts miss firing to the point where it just cuts out. You can be cruising along happily at 70 mph then for not apparent reason it just starts miss firing. Sometimes it recovers and you carry on as normal or sometimes it  completely dies. Once stopped it always restarts again no problem. Any ideas or help appreciated!!

Thanks

Adrian

Does the fuel pump get any noiser when it starts to play up?
How old are ignition bits, spark plugs, HT lead, dissy cap, rotor arm?
fuel filler neck got any holes/rust?

Thanks for your reply. I'll start with the electrical bits. I got the car recently and before I had it it had been in a garage unused for about 8 years so things may have deteriorated.
 

Always worth giving the car a service to see if that solves the problem, if it's been stood in a garage when was the cam belt and tensioner last changed, the parts are cheap and it's straight forward to do if you are handy with car?
Don't forget to change the fuel filter, the one in the engine bay.

Plenty of places to get servicing bits, good place I use but they are delivery only
http://www.carparts4less.co.uk/
Or there sister company which is the same price as car parts 4 less when they have a sale on and you can order on the internet and pick it up in the store http://www.eurocarparts.com/

Also have a look at the fuel filler neck, shine a torch down the filler hose and look underneath.
 

Still no luck resolving this. I've changed the rotor arm, distributor cap, HT leads and plugs. No difference! I've got a fuel filter on order in case it's that. I know it's a basic question but can someone tell me where the fuel pump is located?
Thanks

I believe your car should have 2 fuel pumps, one inside the fuel tank which lifts the petrol out of the tank and one underneath the car, drivers side just in front of the rear beam. It's the one in the fuel tank that normally goes and to get to it remove the back seat base and you will see a round black cover screwed to the floor remove the cover and you will see 2 fuel lines and an electrical connection.
Remove electrical connection and if there is 3 wires going to it then you have a lift pump in the tank as early models did not have a lift pump, remove the 2 fuel lines but have a cloth handy as fuel will spill out of them. You then need to turn the whole thing anti clockwise about 45 degrees, it's like a bayonet connection, I use metal bar with a flat end and a hammer to losen it as it has ridges around the edge. Once lose you should be able to pull it out but it's a fiddle as the fuel pump and the gauge sender has to fit out he small hole so be careful not to break anything.

The pump and fuel gauge sender looks like this.
http://www.ebay.co.uk/itm/VW-mk1-golf-GTI-injection-fuel-pump-and-sender-/281451055002?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item4187ca479a

New lift pump.
http://www.ebay.co.uk/itm/VW-GOLF-MK1-CABRIOLET-MK2-GTI-8v-16v-FUEL-PUMP-LIFT-PUMP-IN-TANK-C246-/200691149226?pt=UK_CarsParts_Vehicles_CarParts_SM&fits=Model%3AGolf&hash=item2eba1fe9aa

Once it's out have a look at the little filter at the end of the pump for rust and bits of grit and shine a torch and check the condition of the inside of the fuel tank, if there is rusty bits in there you can get a magnet on a bit of string to fish out and rusty bits inside and once you get most of it out drop the magnet inside the tank away from where the fuel pump and gauge sender lives and that will collect any rust left.

You may need to fit a new bit of fuel hose from the fuel pump to the sender as they live in petrol disintegrate but make sure it's the same lengh as the old one or the pump will be to high or to low in the tank.

The one under the car is a right pain to replace as it's usually got rusty connections, bosch ones are £100 ish so might be worth to try the lift pump first?

I've been through 4 lift pumps and one main pump in the 200,000 miles and 20 years since we got the car so if the lift pump does not solve the problem it's most likely it will go at some point.

Is the fuel pump relay getting hot as it could also be an electrical problem?
 

Dear mark1gls,
Thanks very much for your detailed response. I'll have an investigate at the weekend.