W202 C36 running rich

[Johnsnz]

Hi All,

A W202 C36 question.

The car is a 95 4 speed and is not ASR equipped it also does not have a cat these we’re not a tequirebt in this market in 95 so it’s never had one.

I changed the plugs today and all 6 were sooty indicative of running rich.

This ties in with the fact the car when idling smells rich if you know what I mean.

It’s not throwing any error codes nor CEL on the dash.

The idle is good and I gave both the throttle body and MAF a clean. This hasn’t resolved the ‘rich’ smell with the car idling.

My question is where to next?? O2 sensor??? New MAF intake air temp sensor??

Thanks in advance…

John S

 

[Jobsworth]

Can you read the live data on the coolant temperature sensor?

 

[Johnsnz]

Can you read the live data on the coolant temperature sensor?

Nah I only have a 16pin obd so need the conversion cable for the Merc round ons connector…

 

[Jobsworth]

You can check the resistance at various temperatures if you search out the data and have an ohm meter. Worth checking. An out of range reading can be seen as plausible by the ecu, -21 degC for example is normal in Alaska and will result in a rich mixture. If the sensor is stuck at a cold reading it’ll remain rich all the time. Negative temperature coefficient sensor means as temperature rises, resistance falls. An open circuit will be seen as extremely cold. Just a bit of background