running rich?

1995 VOLVO 940
120,000 MILES
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M_BUTLER7
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Got a volvo 940 2.3 turbo that's overfuelling, checked the idle control valve and egr valve which seems to have done absolutely anything. Taking a real gamble at the mass air flow meter but still don't no anyone with any knowledge about this query would be very helpful
Sep 22, 2011 at 10:18 AM
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SQM
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Hello,

An engine can run rich due to an issue with the mass airflow sensor (MAF).
Overtime the MAF will get dirty with particles sticking to it and that can impact the air fuel ratio.
You can service the MAF by cleaning it out.

Here are couple of helpful articles:

https://www.2carpros.com/articles/how-a-mass-air-flow-sensor-works-maf
https://www.2carpros.com/articles/mass-air-flow-service

It will also be a good idea to clean out the throttle body as well.
Keep in mind that faulty oxygen sensors can also make the engine run rich.

https://www.2carpros.com/articles/how-an-oxygen-sensor-works
https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor

It can also trigger the check engine light. Is your check engine light illuminated?

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

I have attached diagram for your reference.

Please let me know of any questions.
Thank you.
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Sep 8, 2021 at 9:31 AM