gti running rough when cold

[Bone.]

when i first start my car it's runs like a bag of poo normally on 3 cylinders and is a nightmare till it warms up after that it's fine any ideas?

[Mirage-]

Missing/knackered thermostat causing cold water to be constantly pumped around the entire coolant system until warm? Only saying this because I know that my thermostat is non-existant and I have the same problem although on a warm day it's fine from start.

Gonna be giving her a service at the end of this month so will do the thermostat on it's own and let you know the results before I do the air/oil/fuel filters and oil change if you haven't sorted it before then.

Ian

[Mirage-]

actually thinking about it you say it only runs on 3 cylinders until warm? assuming that you've checked the obvious spark plug + leads for arcing etc. when was the last oil change? My dad said something about dirty oil causing the hydraulic lifters to stick until the oil is up to temp and free flowing properly.

Ian

[tobz.]

Have you got a k-jetronic injection system???
If so it could be the warm-up regulator, this acts like a kind of choke enrichening the mixture during the warm-up period by lowering the fuel pressure. If this is sh@gged the car will usually run rough, be gutless and have real trouble idling until fully warm. Once warm the regulator has no affect on the injection system and the car will run as normal. It might be a pain to get started aswell and you have to keep it on the starter until the revs kind of "wind-up"

If you have a digifant injection system ignore evrything I just said 

[Bone.]

where abouts is it.....is it the warm up valve?

[tobz.]

Yeah it could be refererred to as the warmup valve, it's located on the right-hand end of the block below the distributor. It has a couple of fuel lines going to it and an electrical connector, testing it is difficult though as it requires you to put a pressure gauge in one of the fuel lines, best left to somebody with the proper kit. A replacement warm-up regulator would set you back about £85 last time I checked.

Still assuming you have a k-jetronic though???

[Bone.]

yes it's def a k-jetronic...