Really odd MAF readings...
05-04-2005, 09:01 PM
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Really odd MAF readings... Hi, I just bought a 98 T/A and was scanning it with a Snap-On MODIS scanner. The light was on for an air pump code, but that is an unrelated problem. Anyway I was looking at the engine data and noticed my MAF reading was way off. The Hz was at about 20,000 and the g/sec was 1.3. I know running at idle they should be about 2,000 Hz and 3 or 4 g/sec. Also when I revved up the engine the readings did not change. I unplugged the MAF and the engine ran a little different, but still the readings did not change. The odd thing is that unplugging it set a 'MAF Signal Low' code. How can it set that code when the reading never changed? Just for kicks I swapped out sensors with a LT1 MAF I had laying around, but that didn't change anything. The car runs great, and the STFT and LTFT are never higher than 3 or 4. I am just wondering if it is a problem with the PCM communicating the data with the scanner or if I have the wrong MAF. I have checked the wiring to the sensor and that all was ok. Is there a big difference between LT1 and LS1 MAFs? Maybe someone swapped them out before I bought it? If so how come the car still runs so good? Any advice would be great.
05-04-2005, 09:13 PM
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Do you have an oil performance air filter? If so you may have a bit of oil mudding the maf sensor. Clean it with 'QD electric' see if this helps.
05-04-2005, 09:28 PM
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I do have a K+N filter, and I will try cleaning the sensor like you suggested. Wouldn't the different MAF I swapped out read ok until it got coated with oil?
05-05-2005, 06:16 AM
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The car is stock except for the K+N and a Flowmaster. I will try cleaning the MAF and will take some pictures today. It looks like everything is hooked up right, I have seen quite a few of these cars and nothing looks out of the ordinary. It seems to me like it is working just fine, but maybe there is a problem sending the data to the scanner. If the PCM was actually getting these wierd readings you would think that it would make the motor run funny. Also the PCM knows when it has been disconnected and sets a code for it, even though it won't show a difference in readings.
05-05-2005, 06:11 PM
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I cleaned the MAF today and it really didn't change a whole lot. After cleaning it read 15,000 Hz and 1.2 g/sec. It still doesn't read different when I rev up the engine or when I disconnect the sensor. Here are a couple pics of it: http://photobucket.com/albums/v622/poolshark021/
I plan on getting HP Tuners in the future, but I don't have the money now. I suppose I can wait and fix it then, but I am just wondering if something is set up wrong or if there is a simple fix.
I plan on getting HP Tuners in the future, but I don't have the money now. I suppose I can wait and fix it then, but I am just wondering if something is set up wrong or if there is a simple fix.
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05-05-2005, 06:40 PM
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I have tried 2 different Snap-On scanners and get the same reading. The scanners work just fine on other cars too. Maybe a problem with my PCM?
05-05-2005, 07:06 PM
#10
Originally Posted by poolshark021
I have tried 2 different Snap-On scanners and get the same reading. The scanners work just fine on other cars too. Maybe a problem with my PCM?
Also were both Snap-On Scanners using the same version of software and/or were they both Modis?
05-05-2005, 07:57 PM
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The scanners were two different models running two different software versions. One was a modis with the newest software and the other was a 2500 that hasn't been updated since 2001. Also whats the chances of two different MAFs doing the same thing? Is there a difference between LT1 and LS1 MAFs? I will check the reading right at the MAF but can anyone tell me what I am looking for - how do you measure HZ with a multimeter? Any idea what the voltage should be for 3-4 g/sec?
05-05-2005, 08:10 PM
#12
Originally Posted by poolshark021
The scanners were two different models running two different software versions. One was a modis with the newest software and the other was a 2500 that hasn't been updated since 2001. Also whats the chances of two different MAFs doing the same thing? Is there a difference between LT1 and LS1 MAFs? I will check the reading right at the MAF but can anyone tell me what I am looking for - how do you measure HZ with a multimeter? Any idea what the voltage should be for 3-4 g/sec?
05-10-2005, 03:51 AM
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<-------- stumped....
the best i can give ya is one or 2 guesses...
1. you have a lt1 maf like you wondered....
2. the wire in the wireing harness that brings that info to you has something wronge with it..., get a friend with an ls1 to trade you maf's long enough to rule out #1...
the best i can give ya is one or 2 guesses...
1. you have a lt1 maf like you wondered....
2. the wire in the wireing harness that brings that info to you has something wronge with it..., get a friend with an ls1 to trade you maf's long enough to rule out #1...
05-10-2005, 05:55 AM
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Yea I got a buddy coming over this weekend with an ls1. He has Auto Tap too so maybe his sensor will read different or maybe his scanner will work better. I have checked continuity of the signal wire from the maf to the pcm and the wire is ok. The pcm dispays all the other data just fine on the scanner. I'm leaning towards a problem sending the data to the scanner. The motor runs so good I'm pretty sure the pcm is getting a good reading from the sensor. We'll see this weekend. Thanks again.
05-14-2005, 11:09 PM
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Well I put the Auto Tap on it today and the MAF was reading just fine. It must be a problem sending data to the Snap-On scanners. Thanks to everyone that tried to help.
