Arosa TDi revs high on cold start

[bluearosatdi]

Hi folks. Any clues to a mystery fault please. Arosa TDi AMF engine 86k miles. On start up if engine cranked & fired, revs seem to bounce at about 2000 rpm for 3 or 4 seconds before settling down to idle (almost sounds like engine is hitting an imaginary rev limiter at 2000 rpm). Over last few days with weather colder, revs will stay artificially high at about 1200 rpm for 5 mins and then gradually come down to idle (as if a petrol engine choke was being pushed in ). Car goes well and fuel consumption seems normal. Fault memory shows a coolant temp sender fault. This part has been renewed but the fault does not clear from the ecu. Used to be able to get around this fault by allowing glow plugs to heat for a few seconds longer than usual, but now fault occuring all the time hot or cold. Any ideas please ? Thank you

 

[neil72]

Did you sort this problem ? Daughters car has developed very similar symptoms today ,after start up sounds like its bouncing then idles at 1200rpm for a couple of minutes then its fine ,car drives fine .
Had quick look tonight ,started it 5 times with same results ,did a OBD scan ,came up 17664 ?,cleared code then it started fine ,no symptoms at all .Any ideas ?

 

[Dox1966]

My Golf with a 4 cyl version of the PD engine did this, the code stored was for a coolant temp sensor, changed the sensor and its not done it since

 

[neil72]

Thanks for the info .Did you use a genuine VW part ,as there are some cheap ones on ebay .

 

[Dox1966]

Thanks for the info .Did you use a genuine VW part ,as there are some cheap ones on ebay .

Genuine, buy cheap, buy twice.