Reason for MAF signal not to work?

[BlackMagic]

I sold my GN to my dad, and we are trying to troubleshoot a problem.

The car will start and idle fine, and drive down the street fine. When you mash the gas much at all, the car has hardly no power. Looking at DirectScan I immediately thought I knew what the problem was...a bad MAF. The grams/sec reading only moves between about 5-11 grams/sec no matter how hard the throttle is pushed. We swapped in another MAF, same deal, and then took a known good MAF and had the same issue. We then tried all of those MAFs in another car and they worked fine.

The car has a Translator + and Extender Extreme chip. We sent the T+ back to Mike Licht and it checked out OK. With the key is in the ON position, car not started, one pin on the MAF has battery voltage, the other is seeing 5V. When the car is running, the one side remains battery voltage where the other goes to about 2.55 volts or so. We verified that same voltage is on pin B6? of the ECM while the car is running. Supposedly that reading should be 2.55 or so when the key is on and go to 2.48? or so when the car is running, but it doesn't, it remains at the higher voltage on both the ECM pin and right at the MAF. We have double checked the grounds on the back of the pass head, and even swapped in another ECM to try and isolate the problem.

Any other ideas would be greatly appreciated. TIA!

 

[TurboJim]

A weak fuel pump will do exactly as you described. Once you get to the mid 20's in fyek oressure it will fall on its face off idle, but idle OK, albeit most likely a but rough/rolling,

As for the MAF, once term is 12v, one is ground and one is signal return (to the ecm) I dont know about voltage since its a PWM signal, but you should see a nice square wave, and the frequency should be nice and uniform, You can equate the "pulses" to pp counts which is a setting in the chip that equates the "pulses" to an airflow amount. You may want to verify them. And check your sensor ground, ith the key on at minimum...prefrebly with the engine running (circuit loaded) and make sure there is less than about 0.02v on the ground line.

 

[BlackMagic]

Thanks Jim. I do know the fuel pressure looks good (42psi line off).

I'll check the ground signal to make sure there's not a stray voltage there that might be corrupting the MAF signal.