View Full Version : MAF Sensor Reading
05-15-2008, 08:20 PM
I asked this in the fuel pressure thread, but since it is a totally different topic I thought I would start a new one.
I think my MAF might be going. About how many lbs/min of air should it be reading at idle. My laptop is reading around .22lbs/min. That seems low to me, especially since I took the resonators out.
Has anyone ever looked at their MAF reading at idle? Any idea what it should be?
05-16-2008, 05:15 AM
Air flow is controlled by the throttle plate, which is closed at idle. The intake has very little effect at idle.
05-16-2008, 07:59 AM
Yes but the computer is still reading and utilizing the MAF sensor at idle. If the MAF is sending the wrong signal (telling the computer there is more or less air coming in then there actually is) it will cause problems. That's why I'm asking if anyone has ever hooked their car up to a scanner and actually read how much air is being sucked in at idle according to their MAF. I think mine is reading less air is coming in than actually is, which is causing the car to add less fuel than is required - which is causing the O2 sensor to read lean - which is causing the Computer to correct the condition by adding more fuel - which is causing my fuel trim to state that way more fuel is being used than should be with that amount of air it is reading coming in (just like a vacuum leak).
I know everyone understands this, but I just want to make sure people understand what I'm asking
05-16-2008, 08:21 AM
You are datalogging. What does your tune have your idle sat at? At 1000 RPM's idle my engine pulls .3-.5 lb air/min.
05-16-2008, 10:00 AM
I don't remember exactly, but it was around 750-800 RPM. Like I said it was reading between .19 and .24 lbs/min.
The car isn't running lean enough to trigger a CEL but it's getting there. My long term fuel trim is +18% and my short term fuel trim averaged around +1% (obviously fluctuating for the catalytic converter)
I unhooked the MAF and drove around a little bit. The ltft stayed around +18% (I guess it doesn't change if it determines a sensor is not working), but the stft dropped to -22%. So overall it went from running very lean to a little rich.
Yeah I know I'm going a little nuts over this, but I don't want to spend $150 on a new MAF unless I know it really is on its way out.
05-16-2008, 11:36 AM
why spend 150 bucks on one, you could get a used one for like 20 bucks from a salvage yard. You'd likely have a long enough warranty to make sure it's functioning (even so, how many could you buy from the junk yard before you hit 150 ).
05-16-2008, 11:53 AM
Have you tried cleaning it?
05-16-2008, 12:18 PM
also i have a spare maf itting in my closet that worked great last i checked.
05-16-2008, 12:54 PM
Yeah, I tried cleaning it with MAF spray. Helped a little, but not enough. Unfortunately, where I live now in VA there doesn't seem to be any junkyards within 30 miles :(. Used to be a dozen within 10 minutes of me in NY.
How old's the MAF you've got in your closet? You sure it's good?
05-16-2008, 01:09 PM
yep positive it's good what year is ur car? also if ur idle is 700-800 and ur at .22
and his idle was at 1000-1100 .3-.5 urs sounds about right.
05-16-2008, 03:02 PM
1999 - it's the 6 wire, not the 4 wire
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