MAF Voltage output question - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Taz83 · 10-03-2015, 01:41 PM

Guys I've been searching for the last 2 days and I've had most of my questions answered but I still need a little more information.

I'm running an S13 KA-T hatch with an Enthalpy chip tune, walbro pump, and an N60 MAFS. My problem is a really rough idle and massive amounts of unburned fuel. If I unplug the MAFS, the idle stabilizes and runs smooth but obviously I'm in limp mode after that, no revving above 2500. The moment I plug the MAFS back in, right back to shitty idle and dumping fuel.

So far I've done the full tune up, got a new injector (went bad a few months ago), and today I got a reman MAFS that I got from CarQuest. Still the same problem.

I tested the wires from the MAFS harness to the ECU, they ohm out just fine, 0-0.1 ohms each wire. I have 12v to the power wire, but here's where I need a little clarification.

Please tell me if I'm doing this correctly, but in order to test the signal output from the MAFS, which is the white wire, I'm putting my red DVM lead on the white wire and the black lead to a body ground. Is this the proper way to test for signal output from the MAFS?

The only reason I'm asking is because when I test it this way, I'm getting a reading of 10 volts. My understanding is the signal output should be between 1-5 volts. What are the chances that this reman MAFS I got is defective?

Guys any help is appreciated, I have to leave soon for Florida from Chicago and I'll be driving down. I need to get the car running again. Prior to this, the car was running absolutely fine, albeit a little low on power and a light stumble here and there. This all just happened in the last 2 days. Otherwise I gave everything a check over just a couple months ago when I replaced the bad injector. Also good compression all the way across, mid 170s psi range with a 2-3 psi variance between all 4.

Thanks for any info you guys can help me with.

Croustibat · 10-03-2015, 02:28 PM

Usually MAFs output a 0-5V signal. If it outputs 10V, the ADC in your ECU will read its max expected value, 5V.

I think the problem is in your wiring, not your MAF. Are you sure it should be powered with a 12V signal ? Shouldn't the power come from the ECU ?

Taz83 · 10-03-2015, 02:36 PM

Well the power is coming from the ECU, but it's showing 12V. I've checked the wiring for the MAFS, I didn't see and shorts or opens, but I'll double check.

G-E@Z31P · 10-04-2015, 08:42 AM

The sensor gets 12vdc power, and resists it down to 0-5vdc based on hotwire temperature, which is directly related to airflow...

If you're getting 10, either the afm is borked, or you're wiring it up wrong.

Taz83 · 10-04-2015, 01:13 PM

I haven't changed any of the wiring, just done the normal short/open checks and it's getting the 12vdc power supply. So the way I described I'm checking the signal output voltage is correct then? Using a DVM to test between the white output wire and any ground. That results in a 10vdc reading.

10-03-2015, 01:41 PM	#1
Taz83 Join Date: Jan 2014 Location: Orlando, FL Posts: 4 Trader Rating: (0) Feedback Score: 0 reviews	MAF Voltage output question Guys I've been searching for the last 2 days and I've had most of my questions answered but I still need a little more information. I'm running an S13 KA-T hatch with an Enthalpy chip tune, walbro pump, and an N60 MAFS. My problem is a really rough idle and massive amounts of unburned fuel. If I unplug the MAFS, the idle stabilizes and runs smooth but obviously I'm in limp mode after that, no revving above 2500. The moment I plug the MAFS back in, right back to shitty idle and dumping fuel. So far I've done the full tune up, got a new injector (went bad a few months ago), and today I got a reman MAFS that I got from CarQuest. Still the same problem. I tested the wires from the MAFS harness to the ECU, they ohm out just fine, 0-0.1 ohms each wire. I have 12v to the power wire, but here's where I need a little clarification. Please tell me if I'm doing this correctly, but in order to test the signal output from the MAFS, which is the white wire, I'm putting my red DVM lead on the white wire and the black lead to a body ground. Is this the proper way to test for signal output from the MAFS? The only reason I'm asking is because when I test it this way, I'm getting a reading of 10 volts. My understanding is the signal output should be between 1-5 volts. What are the chances that this reman MAFS I got is defective? Guys any help is appreciated, I have to leave soon for Florida from Chicago and I'll be driving down. I need to get the car running again. Prior to this, the car was running absolutely fine, albeit a little low on power and a light stumble here and there. This all just happened in the last 2 days. Otherwise I gave everything a check over just a couple months ago when I replaced the bad injector. Also good compression all the way across, mid 170s psi range with a 2-3 psi variance between all 4. Thanks for any info you guys can help me with.

10-04-2015, 08:42 AM	#4
G-E@Z31P Leaky Injector Join Date: Sep 2012 Location: Toronto Posts: 126 Trader Rating: (0) Feedback Score: 0 reviews	The sensor gets 12vdc power, and resists it down to 0-5vdc based on hotwire temperature, which is directly related to airflow... If you're getting 10, either the afm is borked, or you're wiring it up wrong. __________________

10-03-2015, 02:28 PM	#2
Croustibat Nissanaholic! Join Date: Aug 2011 Location: France - Toulouse Age: 43 Posts: 1,851 Trader Rating: (0) Feedback Score: 0 reviews	Usually MAFs output a 0-5V signal. If it outputs 10V, the ADC in your ECU will read its max expected value, 5V. I think the problem is in your wiring, not your MAF. Are you sure it should be powered with a 12V signal ? Shouldn't the power come from the ECU ?

10-03-2015, 02:36 PM	#3
Taz83 Join Date: Jan 2014 Location: Orlando, FL Posts: 4 Trader Rating: (0) Feedback Score: 0 reviews	Well the power is coming from the ECU, but it's showing 12V. I've checked the wiring for the MAFS, I didn't see and shorts or opens, but I'll double check.

10-04-2015, 01:13 PM	#5
Taz83 Join Date: Jan 2014 Location: Orlando, FL Posts: 4 Trader Rating: (0) Feedback Score: 0 reviews	I haven't changed any of the wiring, just done the normal short/open checks and it's getting the 12vdc power supply. So the way I described I'm checking the signal output voltage is correct then? Using a DVM to test between the white output wire and any ground. That results in a 10vdc reading.