MAF Voltage Question
06-15-2006 | 02:49 PM
#16
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From: Green Bay Wisconsin
Originally Posted by Randy Page
Tim,
Wouldn't an air leak downstream from the MAF REDUCE the amount of air flowing past the MAF (since the engine is getting some air from a source that is not flowing past the MAF)? If so, I would think that would LOWER the expected voltage coming from the MAF since less air is flowing past it than the engine is actually using. If I understand the operation of the MAF correctly, the more air flow there is, the higher the voltage output should be.
Randy
Wouldn't an air leak downstream from the MAF REDUCE the amount of air flowing past the MAF (since the engine is getting some air from a source that is not flowing past the MAF)? If so, I would think that would LOWER the expected voltage coming from the MAF since less air is flowing past it than the engine is actually using. If I understand the operation of the MAF correctly, the more air flow there is, the higher the voltage output should be.
Randy
I no longer think this is the case. 2.2 volts engine off is too high. 3.8 volts engine at idle is WAY too high (could have the same result with an air leak).
Two bad MAF's in a row is not likely, but possible.
06-15-2006 | 02:54 PM
#17
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From: Mosier, Oregon
The car with the high MAF voltage is supercharged? I missed that. Then it possibly has larger injectors too and other changes to the fuel system?
Originally Posted by Tim Murphy
With the SC connected there is a positive pressure so an air leak down stream of the MAF would give a false higher signal.
I no longer think this is the case. 2.2 volts engine off is too high. 3.8 volts engine at idle is WAY too high (could have the same result with an air leak).
Two bad MAF's in a row is not likely, but possible.
I no longer think this is the case. 2.2 volts engine off is too high. 3.8 volts engine at idle is WAY too high (could have the same result with an air leak).
Two bad MAF's in a row is not likely, but possible.
06-15-2006 | 05:58 PM
#19
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From: Cambridge England
I think that at idle there is no boost with a c/f s/c ? Larger injectors won't affect air taken into the engine at idle, but I suppose the extra power required to drive the s/c might increase the idle volts slightly ?
But not as high as Randy reports...
I hope that isn't one of my rebuilt MAFs Randy ?
But not as high as Randy reports...
I hope that isn't one of my rebuilt MAFs Randy ?
06-15-2006 | 06:20 PM
#20
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From: Bird lover in Sharpsburg
Originally Posted by the flyin' scotsman
Can you swap your MAF with one off of a good running car? One way or another this would fianlise the MAF question.
We have run tests on MAF meters and sensors that tested good here in our shop and put in known good units and fixed the problems.
I wish i had one for a 928 for you to try out.
06-15-2006 | 10:15 PM
#22
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From: Cary, NC
Tim,
Thanks so much for your help. I would not have gotten this far with the diagnosis without your personal assistance over the past few days. I will update everyone with the results of the test with your MAF. Hopefully there is some BBBWWWAAAAAAAA!!!! in my near future!
Randy
Thanks so much for your help. I would not have gotten this far with the diagnosis without your personal assistance over the past few days. I will update everyone with the results of the test with your MAF. Hopefully there is some BBBWWWAAAAAAAA!!!! in my near future!
Randy
06-16-2006 | 01:18 AM
#23
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From: Stockton, CA
Randy
It does seem like a bad/weird MAF....sounds like you will have this fixed soon!!
BTW your wheels look GREAT.....19" carrera classics????? Do you have anymore pics? Also what sizes-offests-tires are you running and do they rub?
It does seem like a bad/weird MAF....sounds like you will have this fixed soon!!
BTW your wheels look GREAT.....19" carrera classics????? Do you have anymore pics? Also what sizes-offests-tires are you running and do they rub?
06-16-2006 | 05:30 PM
#24
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From: Green Bay Wisconsin
I just talked to Randy and he received the MAF I sent.
So far all he has done was plug in the wire connector and turn on the ignition.
Was 2.2 volts with key on and engine off. Now.............. 1.75 volts under the same condition which is within spec.
He is installing new plugs, new o2 sensor, and the used MAF this afternoon and will let us know for sure if that was it.
So far all he has done was plug in the wire connector and turn on the ignition.
Was 2.2 volts with key on and engine off. Now.............. 1.75 volts under the same condition which is within spec.
He is installing new plugs, new o2 sensor, and the used MAF this afternoon and will let us know for sure if that was it.
06-16-2006 | 06:06 PM
#25
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From: Cambridge, Ontario, Canada
Originally Posted by Tim Murphy
I just talked to Randy and he received the MAF I sent.
So far all he has done was plug in the wire connector and turn on the ignition.
Was 2.2 volts with key on and engine off. Now.............. 1.75 volts under the same condition which is within spec.
He is installing new plugs, new o2 sensor, and the used MAF this afternoon and will let us know for sure if that was it.
So far all he has done was plug in the wire connector and turn on the ignition.
Was 2.2 volts with key on and engine off. Now.............. 1.75 volts under the same condition which is within spec.
He is installing new plugs, new o2 sensor, and the used MAF this afternoon and will let us know for sure if that was it.
06-18-2006 | 02:11 AM
#26
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From: Cary, NC
Well, it's confirmed. The MAF was the problem. I guess this just goes to show that you can never rule out a new part being bad out of the box. It just sucks that it took me so long to consider that a posibility. A special thanks to Tim Murphy for all his help!
06-19-2006 | 12:57 PM
#27
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From: Green Bay Wisconsin
Originally Posted by Randy Page
Well, it's confirmed. The MAF was the problem. I guess this just goes to show that you can never rule out a new part being bad out of the box. It just sucks that it took me so long to consider that a posibility. A special thanks to Tim Murphy for all his help!
I had fun working with you to get this resolved. It was kind of like the old days when we first started with the superchargers and talked on a daily base.
