Low Power

[Mark B]

Guys, last ditch effort question... I have a 2005 Jetta Mk4 BEW engine, only 236,000 miles relatively new Garrett VN17 turbo, new Pierberg tandem pump. All vacuum lines are good. Symptom is low power, light black smoke when getting on it, i.e. low boost.

I do have a coolant sensor fault code - question is: has anyone seen where the old black coolant sensor failure caused a low boost symptom? The reason I ask is the original coolant temp sensor has been blamed for many "weird" performance concerns.
Thanks

 

[Nero Morg]

If the coolant temp sensor is faulting out, fuel trim is adjusted to either run rich or lean, depending on what the ecm is seeing for coolant temp. Could be failed reading -100f. They're cheap enough, change it out.