Mr. 9Frank

A while back, soon after cleaning my engine bay (pressure washer ) my Porsche 951 will no longer allow correlation with my LR Quad-M MAF. Having the MAF plugged up will not allow the engine to idle or rev at all. The engine will crank and fire like normal but will not hold an idle at all. Without the sensor plugged in, the engine will crank and start, and after a few attempts will hold an acceptable idle. Once warm, the engine idles fine and allows revving up to about 3K rpm, understandable since the DME has no idea the intake quantity to match adequate fuel.

Ive installed an OE J-boot and AFM with the same result.

The MAF harness has been stripped back and looks clean all the way back to the firewall. The voltage is the correct 12V at the plug.

Ive troubleshooted this issue for some time and need further guidance. Thanks all.

Mr. 9Frank

any ideas...

Rogue_Ant

Is the MAF outputting a voltage to the DME?

Mr. 9Frank

Should the output have a constant voltage that I can check without the engine running?

Rogue_Ant

It will be a varying DC voltage representative of airflow... At idle, I would expect ~0.5volts to ~1.0 volts. With throttle, the voltage should go up.

Additionally, have you tried to communicate with the MAF via laptop? The circuit could have got wet and died...

Mr. 9Frank

My car came with the LR Quad-M and I have been unsuccessful with matching the color coordination with the connection. Blue is power I do know, but there is Green/Red, Yellow/Red, and Green. Of those, which is ground, output, and air temp?

Mr. 9Frank

Yes, I was unsuccessful with linking the device to the software after many attempts. Even having my wife completely delete previous downloaded files and trying for herself. The computer itself will recognized the device has been plugged in, but the Abaco software will not recognize the MAF.

Rogue_Ant

This is the airflow -> voltage output wire:

Mr. 9Frank

Im getting a constant -.2V from the voltage output wire with the key in the on position. Still getting the correct 12V at the red power input wire. Regardless of the air pressure I can blow through the MAF, the output voltage does not change. Is this expected without the engine actually running or is the voltage output totally out of spec?

Rogue_Ant

Sounds like the MAF is dead, or at least not working. I suggest contacting LR, and see if they can help.

Mr. 9Frank

As for my original AFM's similar results when installed, I believe rooted from me not switching the power source back to the correct 5V. I was using the 12V source that was supplied to the MAF. Would using an original AFM cause damage to anything as the DME currently runs a Europroducts 2732A chip set.

Rogue_Ant

Most chips are meant for the original AFM. That said, I have no idea about your Europroducts chip, and what it was intended to use...
The "2732A" is only the EPROM series (what physical chip it is), and does not help identify what is programmed on the chip.

Mr. 9Frank

Thank you, Ive gotten exactly what I need to diagnose further.

Mr. 9Frank

My output voltage is not up to spec. With the AFM wiper arm closed, my output voltage is 0.09v with a consistent increase in voltage up to a maximum of 1.55v with the wiper completely open. My input voltage sits around 4.4v and the ground is good.
In a case like this would you call the AFM bad and look for another or is this an issue which can be addressed.

V2Rocket

Have you tried bending the arm onto a slightly different "track"?