16V ABF Cold idle problem

[technics100]

Hi Folks,

I'm new to Mk3 ownership and picked myself up a 1995 16V Gti a couple of weeks back (135k on it), all was going well until yesterday, I started the car and it wouldn't idle properly.  The revs were hunting and it was going from 600-1500rpm and nearly stalling.  Once warm it was fine.  It did the same thing this morning, after driving 10 miles to work the car is idling spot on around 800

I had a poke about last night, cleaned the TB looked for broken pipes etc, the ISV is buzzing with ignition so it should be working.  while hunting around the net the other thing I thought was the temp sender (one with white plug part number 026 906 161) does that sound like the next logical step?  The car is going really well, revving clean etc.  Also no errors under engine module when checked with one of those wee handheld scanners.  The morning temperature has dropped off the last two mornings, it was 8c today, so don't know whether this has caused the cold start / idle problem

[tweed]

Sounds like your on the right step mate!

Most the time it is that part

[technics100]

Changed the sensor last night and it's still doing it, although not as bad.. would it take any time for the engine / ecu to adjust the fuelling etc?  seems to be hunting at higher revs although still dropping to 600rpm the odd time.. once again fine when warmed up..

Anything else to check?

[vii-cks]

Coolant temperature sensor on my Golf once was an issue, especially with cold starts.

Is that fairly new? That all ruled out?

[technics100]

Yes, changed it last night.. the wee one with the white top and two pins

[tweed]

Coolant temperature sensor on my Golf once was an issue, especially with cold starts.

Is that fairly new? That all ruled out?

Yes replace this with a good quality part and not a cheap copy, as the cheap ones last a month

[Screech16v]

Could be an air leak on the intake manifold and as its warms up the leak seals as it expands a bit.
When cold/hunting try spraying brake cleaner at all the intake joints,revs should change if you hit a leak.

[tshirt2k]

Change all vacuum lines to 3mm id silicone.

[technics100]

Cheers guys, I was away on holiday so haven't really driven it much. How much 3mm hose would I need to do all vac lines?

[tshirt2k]

3m