Does anyone know where I can find a table of values for the MAF sensor in my 4.3L 2004 Blazer?

I read my grams/sec values with a scantool and the results at different rpms are: 5.7 @ 620rpm , 7.75 @ 1000rpm , 11.4 @ 1500rpm , 15.2 @ 2000rpm


I swapped MAF sensors with a friend and the values are a little different as follows: 5.5 @ 620rpm , 7.12 @ 1000rpm , 10.4 @ 1500rpm , 13.75 @ 2000rpm

Although there isn't a lot of difference between the 2 MAF's, is it enough to make a difference in the fuel economy? Or will the O2 sensors just adjust the fuel trim and leave the economy the same?

Thanks for any thoughts on this.

 

Were the mafs cleaned before testing them?

 

You will not find a table that shows MAF readings vs RPM simply because there are too many things that influence the readings. If you were to take readings during two or more seemingly identical runs with the same MAF, the readings would be different.

Also, each MAF sensor can read a bit differently depending on its cleanliness, etc.

The end result is that all of the sensors on the motor combine to give the PCM the data it needs to determine proper spark timing and injector flow rate.

 

Both were cleaned before testing. The test was done with the car at the curb and within 10 minutes of each other so the air temp was the same for both.

I assume that the O2 sensors will trim the fuel in the end and adjust for any differences.

One other difference I did notice during the test was that, with the borrowed MAF, the short term fuel trims went from slightly negative to slightly positive (avg approx. -2.5 to +1.5).

 

Exactly! What Swartlkk said.

If all sensors had to be precise, they would cost a lot more to make. The PCM uses the narrowband O2 sensors to modify the sensor/fuel/performance maps over time.
Otherwise, probably the most precise sensors in the engine are the temp sensors and MAP. This is why you dont see much difference in performance until the MAF sensor gets pretty dirty.

If you look at how they work, any crud on them changes output readings a fair amount.

 

No load MAF readings are pretty much meaningless by themselves. Colder air will show as more air when running over a hot wire MAF sensor. Running at idle with minimal air flow against the front of the truck will likely result in the 2nd run having a higher IAT reading which could explain the lower MAF readings. Worse if you have a typical "cold" air intake without a proper heat shield.