Jump to content


Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse
 

Photo
- - - - -

Mass air flow sensor help needed


  • Please log in to reply
7 replies to this topic

#1 LisaG

LisaG

    New User

  • Members
  • Pip
  • 4 posts
  • Columbus

Posted 10 July 2004 - 01:09 PM

Hi,

I have a '97 Subaru Legacy Outback. Mid-May during a very rainy weekend it began to sputter while driving on the freeway (felt like I had taken my foot off of the accelerator suddenly and then abruptly put it back on) and the check engine light came on. Pulled over and it stalled, managed to get it the rest of the way home. We took it to the mechanics and they said the computer was showing a problem with the mass air flow sensor, would cost around $700 to replace it, but they couldn't be positive that was exactly what was causing the problem. We decided to put off repair and see if the problem persisted. Ran fine during dry sunny weather and would act up again when it began to rain.

Hubby decided to go ahead and replace it himself so we ordered it from AutoZone. For a couple of days it seemed like all was well, no sputtering, stalling, and no hesitation with acceleration. Then it started up again - not as bad at first, and now we couldn't blame it on rainy weather. It was dry and sunny.

Took it to the mechanics again and this is the information that came up "codes that came up were P0102, PO103, PO301, PO302, PO303 and PO404, first 2 codes for air flow signal, signal too high and too low, other codes are misfire codes on all 4 cylinders, mass air flow reads too high at idle 5.1 grams/second, should not exceed 4.8, data showed while cruising that mass air flow will stick at 199.1 grams/second and should be 2.6-16.5 grams/second, circuit from PCM and from MAS to PCM checked good, all data shows mass air flow sensor is fault".

We thought perhaps we had a bad MAS, so we took it back to AutoZone since it was still under warranty. New one was received and installed. Interesting to note - this time with installation the check engine light went out. Went to drive it the next day, check engine light stayed on when I started it and before I could pull it out of the garage it stalled. Needless to say, hubby and I are both at the end of our ropes.

We are wondering if there's some other part that's bad that's causing the MAS to go bad? We're also wondering is there something that needs to be reset or callibrated when a new MAS sensor is installed? We're about ready to take it to the Subaru dealer for repair - but I'll be really upset if they say it's the MAS after we've replaced it twice! :banghead:

Any help and suggestions would be GREATLY appreciated. The car's nearly paid off and I'd love to enjoy a few months without a car payment :banana:

Thank you!

Lisa

#2 The Dude

The Dude

    Certified Subaru Nut

  • Members
  • 798 posts
  • South Carolina

Posted 10 July 2004 - 01:32 PM

Hi Lisa,

I drive a 99 Forester, the MAF sensor died in my car and was replaced for free under a recall. The only symptom I experienced was the "check engine" light came on, and the error codes indicated an improper gas/air mixture. Could you have an actual physical obstruction or leak in the housing leading to the MAF? Perhaps the wiring or the connector to the MAF is failing intermittently. People have killed their MAF sensors by over oiling their after market cloth air filters.
The Haynes Legacy service manual is very helpful. I believe it gives actual "values" for checking the MAF. I would suggest buying a copy. It will save your "hubby" a great deal of time and aggrevation.

#3 mattocs

mattocs

    Subaru Legacy Lover

  • Members
  • 1,312 posts
  • Pittsburgh

Posted 10 July 2004 - 03:03 PM

My MAF sensor went when I was messing with an open air intake. I bought one on eBay for $10 and one at a junkyard for $75.

After you install the MAF sensor, unhook the negitive battery cable for 30 min, then hook it back up. Let the car idle for 5 min.

#4 jcniest5

jcniest5

    Eat, Live, Breath Subaru

  • Members
  • 343 posts
  • The Twin Cities

Posted 10 July 2004 - 05:04 PM

Not sure if this relates to your problem, but (at least my car) if I disconnect the connector to the Mass Air Sensor, my car dies immediately. So, my guess is if it is a problem with your MAS, your car wouldn't even go for a second, it just dies immediately. Not sure if mine is normal or if MAS should be that way or not.

#5 Cougar

Cougar

    Elite Master of the Subaru

  • Members
  • 6,322 posts
  • Anchorage

Posted 11 July 2004 - 12:04 AM

Since you stated this problem first acted up while it was raining I suspect that there is a problem with a wiring connection, possibly at the sensor itself. You have clearly eliminated the sensor as being the problem by replacing it.

Another possibilty is the problem is in the ECU circuit for the sensor. I usually don't look for a problem with these units since they are pretty reliable but in this case it may be the faultly component. Your statement about the problem being sensitive to damp air really leads me to think the problem is somewhere outside the cab of the car.

It would be nice to be able to monitor the MAF signals while you are driving to see how things are. You didn't say how it was determined that the circuit to the MAF was checked out. I assume it was a simple ohmmeter check. If this is so, doing a voltage check or O-scope check to the various wires while things are running may show something up.

Keep us posted on your progress.

#6 sea#3

sea#3

    Subaru Fanatic!

  • Members
  • 354 posts
  • Vancouver Canada

Posted 11 July 2004 - 07:40 PM

LisaG
I would have your technician look at the coil first. It is quite common for the coil tower on your model to crack on the coil towers, people tend to lean on them when working on the engine. Check for corrosion at the coil tower and the high tension leads as well , You can do a quick check by spraying down the coil with a spray bottle and take a grounded wire and hook it around a screw driver . Now move the screw driver over the coil near the coil towers, if every thing is ok nothing should happen. If not it should cause a misfire
The other problem with the Air flow sensor may be related to the misfire,I would fix the missfire then see if the A/F sensor cones back
If the A/F sensor code does come back I would be looking at a wiring problem rather than a sensor problem . The odds that 2 sensor go in that short of time is very slim .
Are you using a stock air filter?

SEA#3

#7 Bill90Loyale

Bill90Loyale

    Subaru Fanatic!

  • Members
  • 423 posts

Posted 12 July 2004 - 02:49 PM

Could you have an actual physical obstruction or leak in the housing leading to the MAF?


Lisa-
Dude makes a good point here. On your upper air filter housing (the thing you lift up to put in a new air filter - and the thing that holds your MAF sensor), there is a black rubber hose that plugs into the engine side of the plastic housing. Make sure that hose is plugged all the way on to the housing. Sometimes it can be loosened or pulled off when the air filter is replaced.

#8 paulad

paulad

    New User

  • Members
  • Pip
  • 1 posts
  • New York City

Posted 18 September 2005 - 04:54 PM

Do you have an ODBII scanner in your tool box? I have one, there good for reading your own cars computer. You have to have faith in what your cars diagnostic is telling you. I am learning about these mas sensors and the motors operation. It took me a few looks at my car before i found a cracked hose on the motor.

The mas sensor is designed into many different manufacturers automobiles, so it would be good to keep in mind when buying any automobile.

My car is a KIA and is eight years old. when i had it serviced in the past it was returned to me with loose intake parts. I am also leary about bringing my car in for service to the dealer , paying high costs and getting my car back in such poor shape. Just keep looking for poor connections and broken or cracked rubber parts. usually finding the bad part or problem, requires taking things apart, digging and inspecting them. The Computer is connected to all the sensors looking for any problem,or change the sensor reports and and adjusting how the engine runs.


Hi,

I have a '97 Subaru Legacy Outback. Mid-May during a very rainy weekend it began to sputter while driving on the freeway (felt like I had taken my foot off of the accelerator suddenly and then abruptly put it back on) and the check engine light came on. Pulled over and it stalled, managed to get it the rest of the way home. We took it to the mechanics and they said the computer was showing a problem with the mass air flow sensor, would cost around $700 to replace it, but they couldn't be positive that was exactly what was causing the problem. We decided to put off repair and see if the problem persisted. Ran fine during dry sunny weather and would act up again when it began to rain.

Hubby decided to go ahead and replace it himself so we ordered it from AutoZone. For a couple of days it seemed like all was well, no sputtering, stalling, and no hesitation with acceleration. Then it started up again - not as bad at first, and now we couldn't blame it on rainy weather. It was dry and sunny.

Took it to the mechanics again and this is the information that came up "codes that came up were P0102, PO103, PO301, PO302, PO303 and PO404, first 2 codes for air flow signal, signal too high and too low, other codes are misfire codes on all 4 cylinders, mass air flow reads too high at idle 5.1 grams/second, should not exceed 4.8, data showed while cruising that mass air flow will stick at 199.1 grams/second and should be 2.6-16.5 grams/second, circuit from PCM and from MAS to PCM checked good, all data shows mass air flow sensor is fault".

We thought perhaps we had a bad MAS, so we took it back to AutoZone since it was still under warranty. New one was received and installed. Interesting to note - this time with installation the check engine light went out. Went to drive it the next day, check engine light stayed on when I started it and before I could pull it out of the garage it stalled. Needless to say, hubby and I are both at the end of our ropes.

We are wondering if there's some other part that's bad that's causing the MAS to go bad? We're also wondering is there something that needs to be reset or callibrated when a new MAS sensor is installed? We're about ready to take it to the Subaru dealer for repair - but I'll be really upset if they say it's the MAS after we've replaced it twice! :banghead:

Any help and suggestions would be GREATLY appreciated. The car's nearly paid off and I'd love to enjoy a few months without a car payment :banana:

Thank you!

Lisa






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users