MAF 1128/1130

[Baconaire]

I thought I'd share my experience since I got a lot of helpful guidance here...

I got my 98 Box in Feb, in April I got a check engine light. Bought a OBDII sensor from Digimoto which connects to a laptop. (Less than $100, I highly recommend). I had 2 codes-1128 and 1130. This indicates a lean condition on both sides of the engine, coming from the O2 sensors. At the suggestion of others here, I cleaned the MAF senor, reset the CEL and did not see the CEL for another 3 months.

In June the CEL came back with the same codes. Again I cleaned the MAF, this time the CEL came back. Check the air intake,filter, cleaned the throttle body, and checked the oil filler. No problems. So I finally broke down and bought the $300 sensor. A very easy installation. Accessing the engine is harder than replacing the sensor. Don't be afraid to do it yourself.

With the old sensor I noted using the ODB sensor that MAF was returning a value of 4 at idle (I forget the units but its like cubib feet per minute or second or some other volume of air per time). Reset the computer. Note that when you reset the CEL, the car will idle rough as it looks for a comfortable idle. Don't be alarmed. I just let it idle and within a minute or 2 its running fine.

Well, now it is running wonderfully. Since I was new to the car, I did not realize that eventhough I may not have had a CEL, the car never ran as well as it could, until I replace the MAF. It is like a new car, the improvement is remarkable. I note that at idle with the new MAF idles at 6.

The moral-just becuase you eliminate the CEL by cleaning the sensor, you may still suffer a performance hit. The MAF may not fail outright, it may read low. So the car beleives the MAF is working, it is getting more air than it is aware of, and responds accordingly, by running lean. P1128-P1130. Look closely at the MAF. Invest in the OBDII scanner if you can, and you will know for sure.

[PTEC]

This is definately the most common cause of CEL's in the 986/996. I get a kick when people try and diagnosis these CEL problems over the internet and people go crazy with ideas of what is causing the faults when 90 percent of the time the MAF is reading high. The fuel system practically never has problems (unless you're taking about the level sender). The MAF hardly ever fails outright. 9 out of 10 times when the car is taking away fuel and setting oxygen sensing faults, your MAF is on the way out and reading high.

Great post.

Edited August 21, 2005 by PTEC

[kdanh]

Baconaire,

I checked the Digimoto website and Porsche is not their make support list. Were you aware of this? They have a new version released v3.7.

[ar38070]

So I am troubleshooting the same problem. Once the car is warmed up the MAF is reading 4.6 g/s (which I assume is grams/sec). My impression from the above post is that this is too low. Does anyone know for sure what the correct reading is supposed to be and under what conditions is the reading supposed to be measured?

[Loren]

So I am troubleshooting the same problem.  Once the car is warmed up the MAF is reading 4.6 g/s (which I assume is grams/sec).  My impression from the above post is that this is too low.  Does anyone know for sure what the correct reading is supposed to be and under what conditions is the reading supposed to be measured?

15 kg/h + or - 1.25 nominal

[Baconaire]

Baconaire,

I checked the Digimoto website and Porsche is not their make support list.  Were you aware of this?  They have a new version released v3.7.

<{POST_SNAPBACK}>

I did not know that. But it works fine. You just have to lookup the translation of the codes. Which is something I would do anyways to double check. Just be sure to get the ISO protocol.