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- Hummer H2 (https://www.hummerforums.com/forum/hummer-h2-8/)

- - Expected MAF readings (https://www.hummerforums.com/forum/hummer-h2-8/expected-maf-readings-40911/)

Expected MAF readings

Hello guys,

I've been trying for a while (and failing) to solve knocking issue on my '05 H2, My scanner keeps throwing knock sensor codes and no MAF codes.

I have decided to look again at the MAF sensor. I replaced it twice in the past and both times the lack of power and knock sensor codes were gone BUT came back after a few miles.
Something is telling me that the MAF or its connection are bad and that is the cause for the knocking.

My scan tool reads 0.01 lb/s at idle and increases to 0.2 lb/s at 5000 rpm (4.5 gps to 90 gps). I have not been able to find the expected readings but, for other 5L + vehicles, I see that it should go to 200 gps at WOT (twice as much as mine). Is this correct?

On the other hand, I tested with a voltmeter the MAF's output and it stays at 2V regardless of throttle position. That is not normal right?

Both grounds look pretty steady when checking for continuity.

Thanks in advance for any info you could share with me!

https://cimg5.ibsrv.net/gimg/www.hum...0a43d5bc8.jpeg

I just installed a Delphi MAF sensor from an Escalade and now at WOT it reads 0.5 (226 mps)

I guess that’s more like it, right?

Should I buy a new Delphi sensor or any advice on a different brand?

https://cimg4.ibsrv.net/gimg/www.hum...034c6ae211.jpg
Fitted a brand new Delphi MAF (AF10043) 19th Jan.

With the engine warm, the Tech2 shows 6.5 g/s (0.014lbs) at idle rising to around 40 g/s (0.088lbs) at 3500 RPM (see JPGs)

Thank you oceanbrave, I am taking now the truck for a day trip and see if the improvements lasts.

Also, in the next few days I should be receiving a pro scanner for some more accurate readings.

Thank you again for the info.

Have you replaced the knock sensors? It a relatively easy job. I'm no expert but I do not think a bad MAF is going to cause knock which will then reduce power. I replaced mine not long ago due to reduced power and it made a world of difference. If you replace the sensors, dont be cheap and also get a new harness.

Best of luck,,

Tim

On the knock sensors, also dont be cheap and get off brand ones.... Spend the extra and get AC Delco. While it is not a very hard job, you do not want to have to replace them again in a year only to find that the generic ones also start spinning when you try to remove them.... then you have to hammer a chisel into them to try and get them back out. I'd also recommend replacing the intake manifold gasket as well if you ever do replace the knock sensors. If its original it will be hardened and flattened with age and much more susceptible to leaking.

Yes, I have replaced the sensors twice... the first time with cheap Chinese ones and the second time with AC Delcos. Also changed the harness but did not change the gaskets.

I think I will try and replace them one last time with gaskets and everything. I have another thread open titled “knock sensors nightmare” 😞

I will keep you posted and thanks again!

you should be able to unplug the MAF and force the truck into Speed Density mode (open loop). The truck should run fine without the input of the 02 sensors and see if it will run without the current issues your seeing. This should indicate if your issues stem from the MAF or something else.

I did this with my sons truck when troubleshooting miss fire issues

Neal

Quote:

Originally Posted by legerwn (Post 358048)

Sounfs interesting! Excuse my ignorance but, how do you force it into “speed density mode”? Just by driving it above a certain rpm/speed?

unplug the MAF sensor,