pp000830

My 1996 check engine light lit up. The Durametric software told me: - Mass air flow sensor not working. I called the local Bosch dealer and found out the part costs over $300. This led me to go through the exercise of cleaning the sensor even though at 80K+ miles I was suspect that cleaning the sensor would solve the problem.
I purchased CRC brand spray Mass Air Flow Sensor Cleaner, remove the sensor from the car and hosed off the sensor with it. Upon closer inspection I noticed the actual sensor element located in the slot of the sensor’s stalk had a gray flat finish on both sides. I sprayed some of the CRC cleaner on some swabs and rubbed the element on both sides until the grey finish rubbed off to reveal that the sensor is white in color and looks like a circuit board with flat components printed on it.
I also sprayed and swab cleaned another smaller pass-through on the stalk near where it mounts to its intake pipe.
I put the sensor back on my car and the light was out! I ran the codes and no sensor code was listed.
The key to success seemed to be using swabs to clean the sensor, as the debris coating on the sensor will not simply wash off from spraying. The hardest part is reinstalling the sensor and air filter housings. The key to this is the sequence of events:
--First put a 7mm socket with flex joint and long extension together. Tape over the tool’s parts so they do not pull apart easily and the flex joint wants to stay strait.
--Slip the assembled tool in next to the idle regulator pipe on the top of the manifold and engage the engine side sensor housing intake clamp ring’s tightening nut.
--Then place the sensor in its approximate position, not attached on its ends or wire. Put the air filter housing in approximate place. Then in place bayonet the sensor housing to the air filter housing.
--Attach the wires to the sensor and the temperature sensor on the air filter housing.
--Next work the air sensor and filter housing as a unit into the intake connection pipe and tighten the 7mm socket you per-positioned above. During this process also orient the vent hose at the bottom front of the filter housing and position the clamp ring on this hose for later tightening.
! If the 7mm socket has fallen off the clamp ring you will need to go back and reposition it.
--Then align the air filter housing on its rubber mounting stalks located under the housing and tighten the clam on the vent hose to the housing.
--I used a very small amount of wax like petroleum lubricant on the hoses, pipes and housings so things would slip together easily. I used the absolute minimum of this to avoid contamination of the Sensor element. I did not use rubber, plastic or silicone lubricant as the effect of these on the sensor is unknown to me.
Andy

Aldestein993

Andy, thanks for the post. Very good info.

BesideTheBox

Andy,

As I have a mass air sensor on order, this is a timely post. Thank you.

Prior to the CEL, how was your engine running? And, did you notice any improvement after cleaning the MAF?

I would think that the air sensor would tell the DME that less air is flowing as the sensor gets dirty. That's an assumption that could be wrong. However, if so, then the DME would adjust fuel delivery downward to compensate, possibly causing the engine to run lean.

Did you disconnect the battery so that the DME would relearn its idle, etc? This was recommended to me to be done if I install a new MAF, wondering if it should also be done if it is cleaned.

pp000830

Car ran fine, had some other codes related to mixture and misfire. They all cleared when I put the MAF Sensor back in. The job can be made easier if it is done at the same time as taking out the idle valve (located top center of the engine) for cleaning. With the idle valve removed the clamp that holds the MAF sensor to the intake is much easier to see and gain access to.
I did not disconnect the battery. I used the OBDC reader software to clear the fault codes.

Andy

bjornebo

I did my annual ISV cleaning this morning and, based on Andy's recommendation, cleaned the MAF Sensor while I was at it (it was last cleaned 20K ago by PO so was due for a cleaning). After a bad experience with a spark plug change a couple of years ago I am a bit gun shy about doing work beyond oil changes and other minor stuff, especially where space is limited and it must be done by feel. However, with Andy's guidance and pictures provided by others e.g., as part of the fuel filter writeup on pcarworkshop http://www.pcarworkshop.com/index.php/993_-_Fuel_Filter
this turned out to be pretty simple. Cleaning both the ISV and MAF sensor took a little less than 2 hours.

nine9six

From what I've heard, the MAF rarely goes bad, and that a good cleaning as Andy describes, will usually remedy any CEL issues.

cdan

[QUOTE=bjornebo;12332113]I did my annual ISV cleaning this morning and, based on Andy's recommendation, cleaned the MAF Sensor while I was at it (it was last cleaned 20K ago by PO so was due for a cleaning). After a bad experience with a spark plug change a couple of years ago I am a bit gun shy about doing work beyond oil changes and other minor stuff, especially where space is limited and it must be done by feel. However, with Andy's guidance and pictures provided by others e.g., as part of the fuel filter writeup on pcarworkshop http://www.pcarworkshop.com/index.php/993_-_Fuel_Filter
this turned out to be pretty simple. Cleaning both the ISV and MAF sensor took a little less than 2 hours.[/QUOTE

cdan

is there a relay between the ecu and the mafs?
cdan