How to: MAF Sensor Test Procedure

[drakesis]

I finally fixed my problem a few weeks ago.... I got rid of the damn truck, lol.

 

[rocco123]

Is this specific to 2nd gen explorers or can I expect the same wiring on my 3rd gen?

 

[2000StreetRod]

2nd gen

It was written for the 2nd generation SOHC V6. I don't have any knowledge on the 3rd generation MAF sensor.

 

[dect]

help needed testing MAF

Sorry for this question but i don't understand how to make contact with voltmeter leads with de MAF connected , how can i do that?

 

[Kanu]

I dont have a voltmeter, but i disconnected my MAf sensor and gave it a little throttle and it still feels like it is misfiring. I changed the spark plugs on the driver side on block a week ago and cylinder 1 was burnt up but the following two cylinders, the plugs were clean.....................should i continue to change all the spark plugs...............?
Im thinking of getting a new MAF sensor anyways just because I dont know when was the last time they replaced the one im using now.

 

[Kanu]

Oh i forgot once i changed the plugs on the driver side the problem cleared up for hours but then came back even worse once i started it back up the next day.................

 

[2000StreetRod]

Voltmeter vs MAF sensor

I dont have a voltmeter, but i disconnected my MAf sensor and gave it a little throttle and it still feels like it is misfiring. I changed the spark plugs on the driver side on block a week ago and cylinder 1 was burnt up but the following two cylinders, the plugs were clean.....................should i continue to change all the spark plugs...............?
Im thinking of getting a new MAF sensor anyways just because I dont know when was the last time they replaced the one im using now.

You can buy a voltmeter from Harbor Freight Tools for about $3. You can clean the MAF sensor with MAF sensor cleaner for a few dollars. I would do both before buying a new MAF sensor for $100.

Misfire is usually due to faulty ignition, faulty fuel injection or low compression in that order.

 

[DoraDaExplora]

GOt The Lean Bank Blues... Not to mention the Timing chain Rattle.... 99 SOHC... Thank you Street Rod... Its people like you that make this place Rock... Still dont have a clue what im doing... ( cant even build a lego ship with instructions) lol.. But you set me in the right direction.. I was gonna just start with changing my manifold gaskets... ( I didnt know what a torx bit was until i took off the dust cover ) I think I will start with cleaning the MAF and go from there.. I FINALY found my PCV Valve... Nice place back there.... No chance Im getting in there to do it.... CHild Labour anyone?? ANyway thank you for your information and Links.. STREETROD = KING OF THE HILL. Daniel from Down Under.... PS: Im gonna buy another SOHC pull it apart and put it back together, just going on this forums links... Who needs lego anyway!!!

 

[georgeaugust]

what happen if it way over like 2,000 rpm is reading 2.0

 

[2000StreetRod]

reading 2.0 volts

what happen if it way over like 2,000 rpm is reading 2.0

In the first post it shows that 3,500 rpm should read 1.9 volts and 4,000 rpm should read 2.1 volts. So 2.0 volts would be about 3750 rpm which is way over 2,000 rpm.

 

[georgeaugust]

2.0

reading at 2,000 rpm at 2.0 v would that make it bog down i took the test while i was driving

 

[2000StreetRod]

more under load

reading at 2,000 rpm at 2.0 v would that make it bog down i took the test while i was driving

The air flow while driving will be considerably greater than when the transmission is in Park or Neutral. As the air flow increases the MAF sensor voltage increases. I don't have any voltages except for Park but 2.0 v at 2,000 rpm in drive may be normal.

How many miles since the fuel filter has been replaced? Have you measured the fuel pressure?

 

[georgeaugust]

The air flow while driving will be considerably greater than when the transmission is in Park or Neutral. As the air flow increases the MAF sensor voltage increases. I don't have any voltages except for Park but 2.0 v at 2,000 rpm in drive may be normal.

How many miles since the fuel filter has been replaced? Have you measured the fuel pressure?

fuel filter,fuel pump, fuel line ,fuel, reg, , plugs, plugs wire, ignition module they all be replaced , i cut the cat off , two different engine doing the same thing , i put the petal to the floor and no power , i'm getting code 111,172

 

[ark]

Background

A nonfunctional mass air flow (MAF) sensor can significantly degrade engine performance. The PCM utilizes the MAF sensor output voltage to determine engine load which is used to adjust the air/fuel ratio during acceleration. The typical engine performance symptoms caused by a dirty or defective MAF sensor are lack of power and hesitation during acceleration. The MAF sensor element wires become dirty with age and become contaminated from excessively oiled air filters. Cleaning the element with MAF sensor cleaner should be performed frequently and often will cure MAF related engine performance issues.

Testing

With the MAF sensor electrical connector connected backprobe the sensor signal (light blue/red wire) and the sensor return (tan/light blue wire) at the connector.

Connect the positive lead of a voltmeter to the sensor signal and the negative lead to the return.

With the parking brake set and the gear selector in Park start the engine.

Monitor the MAF sensor output voltage while increasing engine speed. The voltage should increase smoothly with no dropouts as the engine speed increases. Listed below are representative values.

RPM Voltage
550 0.8
1000 1.0
1500 1.25
2000 1.4
2500 1.55
3000 1.65
3500 1.9
4000 2.1

I know this is an old thread but I'm running into the same problems. Are the rpm/voltage figures that 2000StreetRod posted (above) absolute values? I'm getting conflicting info from another source. According to the other source the actual numbers don't matter as long as the voltage rises and falls smoothly with the rpms. I'm not quite buying into that theory. The readings I get on my MAF are consistently 0.2 to 0.3 volts off from the readings from 2000StreetRod's chart. (94 Ranger, 4.0 / M5OD, as stock as it can be at 235000 miles). Does this mean a bad MAF? My engine is running slightly rough, not bad but not perfectly smooth either. My mpg's are down from 20-21 to 17 and there's a constant rich smell when running. I've already replaced the O2's (yes they tested bad) and tested out the other sensors. I hate to drop $75+ for a MAF without being certain.

 

[2000StreetRod]

No, the numbers are not absolute. Mass airflow varies according to air temperature, atmospheric pressure, relative humidity and engine characteristics. Your 94 Ranger probably has the OHV V6 and my engine has the SOHC V6 so the airflow vs rpm will be different between the two engines. My MAF sensor is integrated with the inlet air temperature sensor which I think started in 2000. Your MAF sensor part number is different than mine and may have different characteristics. Your PCM would be programmed for your MAF sensor characteristics. Also, are you measuring the voltage relative to chassis ground or the sensor return wire? As I recall there's about 0.1 or 0.2 volts difference between the two reference measurements. Have you tried cleaning the MAF sensor element with MAF sensor aerosol cleaner?

 

[ark]

On the sensor ground. Yep, I've cleaned it before and just lately. Thanks for the info though.

 

[ark]

Umm, I boo-booed. I meant on the sensor ground. Sorry 'bout that. I haven't gone from sensor return to chassis (battery) ground. I'll try that as well. Thanks for the tip.
But, I'm still no closer to being fixed than before. Does anyone have any other ideas? I put about 400 miles a week on her, up and down the N Alabama mountains so that 3-4 mpg makes a difference. It hasn't logged any more flash codes since the O2 sensors. I wish OBD1 was a little more helpful. At least then I could put it on a scanner and get a better idea about what's going on in there.

 

[Kevinh71047]

Maf engine. Running
Red 14.30
Black 14.00
Tan yellow between 4.0 and 5.60
Red blue 2.60 and 4.10

Engine off
RED 14.0
BLACK 1.3
TAN YELLOW 14.40
RED BLUE 12.50

 

[2000StreetRod]

Light Blue/Red stripe wire should be the MAF sensor signal
Tan/Light Blue stripe wire should be the MAF sensor return
Measure the voltage between the above two wires while the MAF sensor is connected and the engine is running at idle speed. Then increase the engine speed and see how the voltage changes. The OHV V6 MAF sensor is not the same as my SOHC V6 MAF sensor so the values will be different.

 

[Kevinh71047]

Light Blue/Red stripe wire should be the MAF sensor signal
Tan/Light Blue stripe wire should be the MAF sensor return
Measure the voltage between the above two wires while the MAF sensor is connected and the engine is running at idle speed. Then increase the engine speed and see how the voltage changes. The OHV V6 MAF sensor is not the same as my SOHC V6 MAF sensor so the values will be different.

Ok thanks will take a look and see I'll be glad when this is fixed