pcmhacking.net

Hi immortality, the MAF sensor that is on the car is a genuine AC Delco that has been cleaned and checked for proper flow.

"Injectronics can test, repair and remanufacture many brands of Air Flow Meter (AFM) and Air Mass Meters (AMM), including Bosch, Delco, Delphi, Hitachi, Kefico, Lucas, Mitsubishi, Nippon Denso, Siemens and VDO.
Injectronics tests and calibrates all air meters using an air flow analyser test bench, which flows air through the meter and precisely checks the output of AMM's and AFM's compared to learnt OEM specifications."

I didn't buy one of the EBAY ones but a genuine Delco MAF that was refurbished. All together including this one, I have had 4 MAF sensors on the car, the original one with the screen missing out of it and the wires bent, one from a wreakers that I cleaned with electrical contact cleaner, the one from my VS SS and this one. They behave the same way showing approximately the same frequency, milligrams per second, milligrams per second per cyl. I checked the voltage and the earth to the MAF using the VS manual. Here it gets interesting because the manual says there should be 10 volts to the MAF and mine has 12+, the earth is correct, and the signal voltage with the sensor disconnected and the car not running is showing between 4 and 5 volts like the manual says. One thing that might help is if someone can tell me what their car MAF freq. is at idle and say 2000 to 2500 for me to compare it to.

at 2000rpm it should be approx 3893Hz on a VS V6

idle is at 2440Hz

Thank you Gareth. Mine are higher than that. I'm at work now and can't look at any of the logs, but I think mine is near 3000 at idle. The other measure according to the VS manual was approx. 4 to 9 g/sec at idle and mine is showing less than 1 g/sec. I will look over some of the logs I have when I get home from work today.

Then the next thing would be to swap out the PCM and test.

Good evening gentlemen. I have uploaded a pic of tunerpro screen from weekend log

Looks like I need to resize my photos

On that log when I made it to 2000 rpm my frequency was 5400 and my MAF G/S was only 5.1. After reading Gareths post earlier today I called the place that reconditioned the MAF sensor and asked what they think the idle frequency should be and the said 2470, so basiclly the same as what Gareth said. I spoke to a commodore enthusiast that works there and he too uses tunerpro and recommends it. We covered all the changes I have made to the car and he thought that should have fixed the problem with the over fueling. He too suggested swapping the PCM over to the other one I have.

So when I got home today I swapped PCM's pulled the spark plugs and cleaned them, reinstalled them and started the car. I walked around to the back of the car and it was still pig rich. I went back gave the car a quick rev and shut it off and pulled a plug, almost completely black with carbon. The car couldn't have ran more then 15 seconds. So my plan is to call the place that I got the MAF from and see if I can set up a time that I will be able to take my car there and tunerpro so they can see the MAF readings and hopefully pull it of the car and see how it runs on there test bench. I have left the "new" PCM in the car and will log it on my way to work tomorrow. I am not hopeful that things will be better.

So after finding out what the MAF frequency should be at idle and 2000 rpm, and mine being quite abit higher than that I was thinking of what to do next. I wanted a way to change the frequency for testing purposes with hacking things up. My thought was to shrink the I.D. of the Maf there by allowing less air in. So I turned a piece of acetal to fit inside of the MAF cut it in half and trim the ends to make a tight fit and decrease the diameter by 8mm. Installed them on the back side of the MAF and started the engine. Instead of the frequency dropping lower, it raised up to 3300 at idle. Then it dawned on me what I actually did was raise the air speed, effectively raising the frequency. Drats!

So that led to the next conclusion, if choking the air increases the air speed thru the MAF than increasing the air volume should slow it down. I think I mentioned earlier that the car was duel fuel when I got it and the gas wasn't working. To get the roadworthy the mechanic told me to pull it all out, so that's what I did. So I thought if I reinstall it I can do what ever I need to so I can add an adjustable vacuum leak. The rubber elbow leading into the TB was about 6mm thick so I drilled a hole in it and installed a petcock. Now I can adjust the vacuum leak to get the frequency down to where it needs to be. At idle I have it at approx. 2450 so we'll see how it runs tomorrow on the way to work. This is only a temporary set up to see if I lower the frequency will the over fuelling problem subside. All of this has made wonder if the car would have been retuned when the gas was installed. Also I noticed in tunerpro there were tables mentioning the MAF frequency, so is fuelling adjustable to the MAF frequency?