1. Home
  2. Automotive Technologies
  3. Data on normal readings from sensors?

Data on normal readings from sensors?

Hi All,

I'm working on a pesky little problem on my 2000 Chevy Astro/4.3L AWD minivan. The thing keeps lighting the MIL with a code of P0101 - something about the MAF sensor readings being out of spec.

I connect my OBD-II monitor to the car and I can see the MAF go from .7 lbs/min to about 5.x lbs.minute as I accellerate, so I know that the sensor is doing something.

My question is about where to find some typical readings information. I.e.: what *should* the airflow be under normal acceleration, at idle, etc.

Thanks!

Reply to
TomO
Loading thread data ...

You can download a volumetric efficiency calculator here;

formatting link
Should calculate grams per second based on RPM, temperature, engine size, air density (baro) etc. I'd plug in 85% for the (your) engines VE

Reply to
aarcuda69062

Thanks.

If I'm using this tool correctly, I see that in order to reach near 100% Volumetric Efficiency, I would need to see about 12.5 lbs/minute at 2200 RPM and a reading of 10.7 would yield me pretty darned close to 85% VE.

So it sounds like I have an airflow problem to troubleshoot, or perhaps a vacuum leak beyond the MAF sensor or something along those lines.

Reply to
TomO

Well, I did find a vacuum leak. It was a broken plastic line that feeds the dashboard air controls. Got that patched up, but the readings from the MAF sensor did not change significantly. I'll have to dig deeper I suppose.

Reply to
TomO

You're not going to reach 100% volumetric efficiency with that engine. The idea is to plug in a known reasonable volumetric efficiency and then fill in the other variables to see if your air mass measurements agree with what they calculate out to be.

An engine of XXX cubic inches will flow XX grams of air per second (or lbs. per hour) at XXXX RPM at XX.X barometer.

Could be a measurement problem (faulty sensor), could be the engine isn't breathing as well as it should be (coked valves, valve timing problem, restricted exhaust, restricted intake).

The engine is an air pump, the mass air flow sensor give a way to measure the air being pumped thru the engine. Either the sensor is wrong, the engine can't pump its volume or the problem lies elsewhere.

Reply to
aarcuda69062

That's true...I've seen crimped tailpipes cause MAF codes before...go back to basics, blow the dust off the vacuum guage and see what kind of vacuum level you are pulling...

Reply to
jeffcoslacker

Yeah, I was just working theoretical numbers to see if I was doing the calculation correct.

I found a broken vacuum line, but repairing it did not help the readings from the sensor. It did get my dashboard air ducts working again though.

I'll just keep on checking stuff until I come to the true source of the problem.

Thanks!

Reply to
TomO

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.