Hi 89-300CE. Unfortunately, I can't do any testing myself. No tools; no garage.

This was the only test the mechanic did and he says the compression is 'excellent'!?

So, relaying what he told me, the car is running very rich. All the plugs are carbon fouled. The O2 sensor is showing an error.

He replaced the fuel regulator and says there is no point replacing the 02 sensor till he is sure it is not something else that is causing the car to run rich. He asked me to run a few more tanks through the car to clean it out. Fuel consumption is 4 km per litre so that won't take long!!

I am begining to think I should get a second opinion - and full compression test - from another garage.

How do you test for closed circuit mode?

Also, do you know what the factory compression spec and range is for the M104 - I guess yours is the M103. 190 seems high. I need to go buy a manual.

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My previous car was a Honda