Black smoke from exhaust

[mforos]

Hello there,

Every time I go for a drive, I need to wash the rear of my white 3.2 Carrera as it has black soot all over it.

Although spirited driving makes it worse, cruising or a short trip means the rear engine lid, rear quarter panels and rear bumpers are dirty. It appears to run well otherwise.

With my limited knowledge, I'm assuming the car is running rich as the soot is not oily, the car does not use any oil but has poor fuel consumption.

Again, with my limited knowledge, I have looked at the air flow meter and tested its resistance per the Bentley manual.
As the flap (door) opens, it starts at about 600 ohm, rises to about 1,200 ohm and as I continue opening the flap will then drop back to about 900 ohm. Is this correct?

Am I on the right path here or is it something else i should be looking at?

Thanks for your help!!!

Michael

[twistoffat]

Sounds like fuel. Blue smoke would suggest oil and possibly worn valve guides

Have you done anything to the Car lately? It could be an O2 sensor or Plugs. The O2 sensor when tested should run at approx .08 Volts.
If its broken the mix will run rich as the voltage output drops

[Jaskas]

Too much oil in the engine? Have you tested the oil level while engine is running on idle, on flat surface and warm.

[Jack Olsen]

Stuck injector/s? How's the mileage?

[E Sully]

Does your car have an O2 sensor? Have you checked your cylinder head temperature sensor?
You can check your AFM by using a 9V battery following this link.
Air Flow Meter (AFM) - from "The 944 Motronic DME" by FR Wilk

[Techne]

hmmm. My white 3.2 does the same thing. 13MPG and a sooty rear end.

[mforos]

Hi all - thanks to all those who have replied, I greatly appreciate your time.

The following are replies/answers to your much appreciated suggestions.

E Sully - the car does not have an oxygen sensor as is an early Australian (ROW) delivered vehicle, I have however checked the cylinder head sensor and appears to be ok. I tested the AFM following the steps in the Bentley manual which suggests it be done without any voltage going through it? Reading the link you sent me makes far more sense how I should test it so I will try again with voltage running through it.

Jaskas - Oil level is at correct level (half way between the marks) which I check regularly but have never needed (yet) to top up so does not burn much oil.

Jack Olsen - Mileage is a poor 25-30 L/100 Km (8-9 mpg) so a stuck injector is a possibility - any advise what to do?

Thanks again everyone, would love to hear more suggestions!

[mforos]

Hi all - thanks to all those who have replied, I greatly appreciate your time.

The following are replies/answers to your much appreciated suggestions.

E Sully - the car does not have an oxygen sensor as is an early Australian (ROW) delivered vehicle, I have however checked the cylinder head sensor and appears to be ok. I tested the AFM following the steps in the Bentley manual which suggests it be done without any voltage going through it? Reading the link you sent me makes far more sense how I should test it so I will try again with voltage running through it.

Jaskas - Oil level is at correct level (half way between the marks) which I check regularly but have never needed (yet) to top up so does not burn much oil.

Jack Olsen - Mileage is a poor 25-30 L/100 Km (8-9 mpg) so a stuck injector is a possibility - any advise what to do?

Thanks again everyone, would love to hear more suggestions!

[E Sully]

Check the spark plugs. If they differ then you can isolate the problem cylinders. If all are the same, then it is the motronics. So much excess fuel can contaminate lubrication system.

[E Sully]

Specs for CHT. Other options are to check Altitude Correction Switch, or speed sensor.

[mforos]

Thanks for the info Ed.

I have crudely tested the CHT sensor by unplugging it while the car was running. It really didn't like it when I unplugged it so I assumed all was ok. However, it is the older single pin connector so will upgrade to the newer type as a matter of course as it might be giving false readings at different temperature ranges.

I definitely will change oil as a safety precaution. Although it looks clean and in good condition, better safe than sorry.

Injectors are a possibility, I will check one by one as well as test fuel pressure and re-test my AFM with voltage running through it this time!!