Hello!

in the search of what is wrong...

the current coolant sensor has a resistance of 1708ohms while the old one from my old non black smooking engine is1833.

my mechanic insist that the black smoke is a faulty coolant sensor.

 

And also, what is the sensor in the air filter box for?

That sensor has no continuity, means it is broken, no electricity or signal can cross, isnt supposed to have some resistance?  (that one has LOT of time in that state)

 

and also

what is this vent or duct for? (it is sealed to avoid dirty air to enter) where is it to be supposed to be connected to?

 

 

 

Looks like air temperature sensor in the airbox and the blocked connection is probably for a breather pipe.

 

The coolant sensors never give the same reading because the tolerance is +/- 10% if you're lucky, it isn't critical and both seem to be working ok.

 

Check the cam and fuel pump timing Kharl, the mechanic is an idiot.

I can't find it just now, but there's a graph somewhere of expected resistances of the coolant temperature sensor, and it has quite broad ranges at each temperature.  I suspect yours are reading within that range, at whatever temperature you checked them.  

Lower resistance means warmer temperature reading, so the one at 1708 will be telling the engine management that the engineis slightly warmer than the other one, therefore unlikely to result in overfuelling.

 

The device in the airbox might be either an incoming air temperature sensor*, or a thermoswitch, which would change between open and closed circuit at whatever threshold temperature it has.  Take it out and examine for a part number.

 

*item 15 here, apparently: intake connection; air filter with connecting par... - Fabia(FAB) [EUROPA 2001 year] (7zap.com)

 

 

Edited 18 August, 20214 yr by Wino

55 minutes ago, sepulchrave said:

Looks like air temperature sensor in the airbox and the blocked connection is probably for a breather pipe.

 

The coolant sensors never give the same reading because the tolerance is +/- 10% if you're lucky, it isn't critical and both seem to be working ok.

 

Check the cam and fuel pump timing Kharl, the mechanic is an idiot.

Alright.

 

You have no idea what i am dealing with these mechanics

44 minutes ago, Wino said:

I can't find it just now, but there's a graph somewhere of expected resistances of the coolant temperature sensor, and it has quite broad ranges at each temperature.  I suspect yours are reading within that range, at whatever temperature you checked them.  

Lower resistance means warmer temperature reading, so the one at 1708 will be telling the engine management that the engineis slightly warmer than the other one, therefore unlikely to result in overfuelling.

 

The device in the airbox might be either an incoming air temperature sensor*, or a thermoswitch, which would change between open and closed circuit at whatever threshold temperature it has.  Take it out and examine for a part number.

 

*item 15 here, apparently: intake connection; air filter with connecting par... - Fabia(FAB) [EUROPA 2001 year] (7zap.com)

 

 

The mechanic, which  "has experience dealing with diesels german cars" says that sensor is a  MAF. And i say  o,that is for gasoline cars.

 

And for  being a MAF it  must have been installed where the air cross it directly tru it

It is not a MAF, but many diesels do have one fitted.

He doesn't sound very good.

Today morning heading t the mechanic i toke a highway and there is no black smoke.

I just replace the coolant sensor yesterday.

Maybe the other coolant sensor was reading incorrectly when warmer/hot.

Test it in some near-boiling water,  carefully,  if you are curious.

It will take a little while for the temperature to affect the NTC thermistor within, so be patient.

1 hour ago, Kharl said:

"has experience dealing with diesels german cars" says that sensor is a  MAF. And i say  o,that is for gasoline cars.

He's maybe right; at least some VAG diesels do have a MAF. I don't know about the SDi though.

7 minutes ago, Wino said:

Maybe the other coolant sensor was reading incorrectly when warmer/hot.

Test it in some near-boiling water,  carefully,  if you are curious.

It will take a little while for the temperature to affect the NTC thermistor within, so be patient.

Uhm.. alright

And what consequences has to run the car without the air intake temperature sensor?

34 minutes ago, KenONeill said:

I don't know about the SDi though

No such device evident on the wiring diagram.  They'd always be more than 2 pin though, I think; and as the OP says, mounted in flowing air.