MAF Sensor test - really true?

birgerfromvictoria · Post by **birgerfromvictoria** » 12 Sep 2011, 20:38

Hello everybody,

For a while, I'm trying to figure out if my 1998 V70 T5M (143tkm) has a bad MAF sensor. I'm not really a car person and VERY far away from being a "real" mechanic but I'm also cheap and try to see if I can figure out a problem before going to a shop or dealership.
I got infrequent DTC P0103 and suspect a faulty MAF sensor. Yesterday, I read on the almighty interweb (think i've got to give James May the credit for this joke

that a faulty MAF sensor reveals itself by letting the engine die when unplugged with running engine and then pluggd back in. Sounds too easy for me - does anybody know?

Thanks everybody!

Post by **mvsuzr** » 12 Sep 2011, 20:59

This is a quick way to check it, if your car is running bad all the time. When you unplug the MAF the computer sees the failure and goes to a "backup plan" that smooths out the rough running (if the sensor was causing it). When you plug it back in the engine will get rough again.
If the engine runs rough with the sensor plugged or unplugged, it's probably not the MAF.
If your car runs good but you get an occasional code, this type of test probably won't help.

SimLyons · Post by **SimLyons** » 12 Sep 2011, 21:20

Then again.....While working on my 97 850R I forgot the plug the MAF back in. It would start and idle fine, but as soon as I put it in any gear it would die immediately. It would not run under any condition other than Park or Neutral. My MAF was good as long as it is plugged in (duhh).

Post by **jimmy57** » 12 Sep 2011, 21:22

Way back when the 98's were new there was a campaign, a lengthy one with 7-9 things to check and correct. One of the things was to spray a cleaner on the MAF connector and then plug/unplug a few times and then cable tie the wiring harness to MAF to the MAF body. The harness being loose was cautious erratic signal or no signal at times. It's worth a try since it is easy and cheap. You can use WD-40 or other penetrating spray as the cleaner.

birgerfromvictoria · Post by **birgerfromvictoria** » 12 Sep 2011, 21:29

Thanks for the posts. I cleaned the MAF with MAF cleaner from Canadian Tire after I got the p0103 for the first time approx two weeks ago. I'll try the "tie down" tomorrow.

birgerfromvictoria · Post by **birgerfromvictoria** » 12 Sep 2011, 23:18

Mmmh, if this is the quick way to test the MAF - what would be the correct way?

Post by **jimmy57** » 12 Sep 2011, 23:29

The cleaning i was talking is the connector, not the element in the airstream. The correct way is to monitor the MAF signal with a scan tool and also to view the signal on an oscilloscope.

birgerfromvictoria · Post by **birgerfromvictoria** » 13 Sep 2011, 00:07

Oh, I see. I don't have this kind of equipment. I'll clean and tie the connector tomorrow and see if the etc comes back. Thanks for the help so far.

birgerfromvictoria · Post by **birgerfromvictoria** » 13 Sep 2011, 23:38

Cleaned and zap strapped down. No cel so far - let's see how it goes. Thanks everyone.

Fosgate · Post by **Fosgate** » 14 Sep 2011, 00:34

Please keep us updated as I'm having the same problem as you ....
I do have an oscilloscope handy but my car does this intermittently so I cannot drive around with an oscilloscope and hope it will start playing up for me to check