Poor running MK1 Golf GTi Cabrio

[m1ck66]

Hi, I have a Mk1 Golf GTi Cabrio. It has a Digifant 8v GTi engine in it. It is experiencing running problems. It has been off the road since last summer due to new bushes etc and I only use it for summer. I was getting it ready for the MOT when it started to fail to start. I changed the fuel pump relay as this was not getting power. The problem remained. I can start it up ok and it runs and revs freely until it gets warm. Then it will not rev past idle speed at all and occasionally makes a loud clunking sound. If I turn it off and leave it for 10 mins it starts ok again and then developes the same problem when warm. Is there something simple I am missing or is there some obvious order for process of eliminationto locate the problem? I am leaning more towards an electrical problem now.

Cheers, M1ck66

[rubjonny]

I'd start with the ecu temp sensor, its located in the flange on the front of the head.  it will either be a push fit blue sensor or a screw fit white sensor.  Also check out the digifant tuning guide in the MK2 maintenance + info section

Also check the filler neck for rust, if there is any replace it asap, but it sounds like the damage has already been done!
take out the rear seat and you'll see a round metal disk, under this you'll find the lift pump/fuel level sender, pull this out and check for rust and debris in the filter.  if there is any, get yourself a magnet on a piece of string and swish it around the hole, shake the car as much as possible and pull the magnet out.  Clean any rust off it and repeat till it comes out clean.  Chuck the magnet back in and refit the pump, brim the tank and drive it for a week, recheck the magnet.  Keep at it till no more rust comes out!

[m1ck66]

Cheers.

Fuel filler neck already replaced, will now check the filters in and outside the tank.
I already fitted a new inline filter before the fuel rail a few weeks ago and it ran fine then.
The trouble started when i wasn't getting power to the fuel pump outside of the tank.
I will post if i get any joy.

[rubjonny]

did you check the plug for voltage or was the pump just not running? rust inhalation could have damaged it 

[m1ck66]

Checked filter and pump in tank, cleaned and seem ok, stripped accumulater off and cleaned and still no joy. Any ideas where to try next?

[rubjonny]

is the pump still giving you power issues?