Touareg: 2008 V8
Join Date: Nov 2015
Location: Colorado, United States
Second Vehicle: Other
Thanked 136 Times in 132 Posts
Do you have VCDS? That will tell you what your temp sender is telling the ECM.
If the ECM is getting the wrong coolant temp, the fuel mixture could end up being wrong.
That also explains the idle speed error. If the ECM thinks the coolant is cold, it will enrich the fuel mixture AND bump up the idle speed to warm up the engine faster. Conversely, if it thinks it is already warmed up, the idle speed will be too low (for the actual temp) and the mixture will not be rich enough for decent idle when cold.
That is, IF the coolant temp sender really is bad.
No VCDS? Get it here:
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