MAF sensor "bubbling"? Volvo 850 1995

classical · Post by **classical** » 17 Dec 2025, 08:09

Is that kind of "bubbling" on MAF normal? See the picture. Can that be a reason for the car running rich? Oh, and, by the way, these bad MAF signal numbers can tell that the MAF harness or the wire is bad, am I right? Terminal 4: 0,08 V; terminal 3: 0,02 V; terminal 2: 1,43 ohm; terminal 1: 0 ohm (the values are taken from the harness when the locker of the harness is upward on the harness, and as the power is on). What else can be the cause of these numbers? I appreciate answers.

Post by **scot850** » 17 Dec 2025, 08:32

How long have you owned the car? It is possible someone has used something unsuitable for cleaning the MAF at some point in it's life which has reacted with a coating on the surface or the material it is made from.

The 3 main reasons for running rich for me are:

1) MAF failing
2) Dirty throttle body
3) O2 sensors failing

There are other causes like air/vacuum leaks but those are more likely to cause lean running.

What is the condition of the spark plugs/wires/distributor cap/rotor? With those, brand can be important.

Neil.

classical · Post by **classical** » 17 Dec 2025, 09:54

Thank you for the answers! I have owned it about three years. I guess it is possible that some unfit chemical has been used in MAF's cleaning, but I cannot know for sure. About a year ago I changed the O2 sensor, and as I recall it, after that the running rich started. I just ordered a new sensor which, at least, is the right one for Jetronic. So it will be interesting to see what happens when I replace the O2 sensor.

I checked vacuum leaks with the old break cleaner test, and did not find any. I cleaned the throttle plate about 1 1/2 years ago but have not cleaned the throttle body extensively. I should. Thank you for the idea. I changed the spark plugs about a year ago, and since the car has been running rich, they have gotten dirty quite fast; and I cleaned them once. I should check them again, and I have been planning to check the ignition side – the distributor, the ignition coil, etc.

I was mainly wondering that "bubbling" MAF and the harness' bad signals – could they also cause running rich. And should I change the harness and the wire, if I can find a replacement – but it would be a big task I guess. Would it be, by the way? At least the MAF does something, because when the car was idling and when I pulled the MAF plug off, the engine stalled.