MK5 Golf GTI

All Things Mk5 => How to Guides / Troubleshooting => Topic started by: jimmy-s3 on April 17, 2011, 10:37:04 am

Title: Cold start switch/sensor
Post by: jimmy-s3 on April 17, 2011, 10:37:04 am

Still having problems with my car from cold start up.......

Does anyone know which sensor/switch controls the cold start valve?? I want do disconnect it and see if my car drives any better from cold without the cold start not operating...

Title: Re: Cold start switch/sensor
Post by: jimmy-s3 on April 18, 2011, 07:01:19 pm

Does this mean no one on this forum knows??

Title: Re: Cold start switch/sensor
Post by: ub7rm on April 18, 2011, 07:55:15 pm

I thought it just went off the coolant temp sender / lambda temp and the fuelling was adjusted until the cat was up to temp.  Could easily be wrong though  :rolleye:

Title: Re: Cold start switch/sensor
Post by: Richn83 on April 19, 2011, 09:07:34 am

I think its a relay someone posted up something about blower relay when joesgti was having cold start issues on his R32 could be worth a search for that thread as a starting point.

Title: Re: Cold start switch/sensor
Post by: ub7rm on April 19, 2011, 11:09:48 am

The 1.8T had a secondary air injection system which involved pumping lots of air through the cat when it was cold - the R32 of a similar vintage (non FSI) might have the same thing but I think the FSI system did away with having to have this type of secondary air injection system in place ... again I stand ready to be corrected.

Title: Re: Cold start switch/sensor
Post by: jimmy-s3 on April 19, 2011, 07:52:52 pm

Ive been told its probs the thermostat temp sender unit or the fan temp switch.
Has anyone changed theirs?

Title: Re: Cold start switch/sensor
Post by: ub7rm on April 19, 2011, 10:00:32 pm

Quote from: jimmy-s3 on April 19, 2011, 07:52:52 pm

Ive been told its probs the thermostat temp sender unit or the fan temp switch.
Has anyone changed theirs?

I changed the engine temp sender in the winter as I felt the car was taking far too long to warm up and thought it might just be a dodgy sensor.  Intermittently it would be more difficult to start in the cold and when it was like this the revs would drop straight down to the 'normal' reading rather than sit high for 30 seconds or so then drop down to normal.  The temp sender didn't sort any of this and I've just accepted that its 'normal' as the car drives fine and cold starts seem to be a little bit of an issue for FSI engines.  Quite straightforward and relatively cheap to do though ...

AFAIK the fan temp switch doesn't make the ecu do anything other than switch the rad fans on or off.  The engine temp sender affects the fuelling etc.

Title: Re: Cold start switch/sensor
Post by: jimmy-s3 on April 21, 2011, 05:36:59 pm

Im not sure what to do then?
Is it the tumble flap valves that control the air to get the car up to temp??

Title: Re: Cold start switch/sensor
Post by: jimmy-s3 on April 21, 2011, 09:44:57 pm

My car seems to have similar symptons to the one in the link below..
I have not checked the control arm yet but im sure the last time i looked,it was still connected. I suspect the flapper motor is stuck or sticking on mine!??
I had a code reader on my car yesterday and no fault codes were brought up.

http://myfastgti.com/volkswagen/threads/9250-more-intake-manifold-runner-control-flap