Unstable idle when cold - camshaft sensor?

Olerype

Member
TDI75 AMF about 110kmiles

When cold, the engine has a unstable idle hunting between about 800 to 1200rpm. After 1-2 minutes the idle stables just fine. If the engine is hot, no issue with idle.

Sometimes engine needs some extra cranking to fire up. This happens only when cold.

No fault codes.

Is this poor camshaft sensor? (tried to search forum as I guess this is a typical fault, but did not find any threads that matched)
 

a2adam

New Member
Coolant sensor if faulty tends to give it the shakes .

Sent from my Pixel 4 using Tapatalk
 

Olerype

Member
Got me thinking; is it possible to see what the coolant and camshaft sensor reads by using VCDS?

The cluster show correct temp. but the coolant sensor is a dual type, one for ECU and one for cluster?
 

Robin_Cox

Member
With an ODB reader (and VCDS obviously) you can poll both feeds from the coolant temperature sensor ; engine side is in the engine ECU measurement blocks ; dashboard needle side is in the dashboard measurement blocks. These are separate readings but should be identical. Useful to diagnose whether one of the feeds is malfunctioning.

Don't know about camshaft sensor.
 

dieselfan

Member
The cluster show correct temp. but the coolant sensor is a dual type, one for ECU and one for cluster?
Yes, so a good reading of the cluster is no proof of that the ECU get correct numbers

I have two AMFs on stands so tell me if you need parts to test with, I can bring them to Arendal.
 

Olerype

Member
Thanks for generous offer!!

I will need to check VCDS later as I have little time for the moment. The car drives just fine, just strange idle for 1 minutes in very cold mornings.
 
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