mass air flow

[Lifted92]

does anyone know how to test one or know the ohm resistance of a mass air flow for a 92 explorer. thank you.

 

[Roadrunner777]

This is the best site I know of for MAF issues:

http://easyautodiagnostics.com/ford_maf/maf_sensor_ford_1.php

 

[Lifted92]

Thanks Roadrunner that web site helped a lot. I was trying to look for volts and ohms to test it like an IAC Valve but its a little different. now I'm off to do some MAF testing and hopefully this is my problem because if not I'm stumped. Thanks again Roadrunner you've helped me out a number of times on here in the past couple weeks.

 

[Roadrunner777]

Right... the MAF is what you might call a semi-intelligent sensor. There are electronics and signal conditioning built into it.

Anyway, glad to help. I'm just another person trying to get their Explorer to run as well as it can, I'm just a few months ahead of you in the process.

Good Luck!

 

[Lifted92]

i just finished following the test procedure for the mass air flow and everything was in line. i had 12 plus volts for power and my 2 grounds and the signal wire went from 1 volt and increased smoothly up with the increase in throttle. my question to the test though is how does it test the sensor. when i read how to do the test i said great that's what i need. while doing the test its testing voltage to the sensor and not actually testing the sensor itself.

 

[Lifted92]

My question is what would cause high idle in park, normal idle in drive but when you touch the throttle it falls on its face and stalls out. after it stalls its very hard to start. I have replaced the TPS about 1 month ago and the IAC valve 1 week ago.

 

[Roadrunner777]

i just finished following the test procedure for the mass air flow and everything was in line. i had 12 plus volts for power and my 2 grounds and the signal wire went from 1 volt and increased smoothly up with the increase in throttle. my question to the test though is how does it test the sensor. when i read how to do the test i said great that's what i need. while doing the test its testing voltage to the sensor and not actually testing the sensor itself.

The signal wire is reporting the amount of air flowing through the sensor, so for it to go up with throttle is perfectly normal and a good test result. That wire ends up feeding the engine computer as an input to calculate the fuel injection pulse.

 

[Roadrunner777]

My question is what would cause high idle in park, normal idle in drive but when you touch the throttle it falls on its face and stalls out. after it stalls its very hard to start. I have replaced the TPS about 1 month ago and the IAC valve 1 week ago.

When it stalls and is hard to start, you can do your best troubleshooting. This is kind of standard no-start troubleshooting. Pull a plug wire and crank it. Spark?

Pull an easy spark plug and see if it is wet with gas.

Oh, you know what does this sometimes. There is a vacuum line that goes to the fuel pressure regulator. It is used to compensate fuel pressure for manifold vacuum, so the injectors get a good pattern.

Sometimes, the fuel pressure regulator leaks internally, and raw fuel gets sucked down the vacuum line. That dumps raw gas into the intake manifold, which would result in high idle, low vacuum, and flooded cylinders, causing hard starting. Ok, here's the drill. Get it running, then shut it down normally. Go to the vacuum tree on the intake manifold and pull/plug every port and line. If one of the lines has gas in it, you can stop there, that's diagnostic for a failed fuel pressure regulator. Anyway, pull and plug everything and see if it starts up and runs well.

If so, start hooking the lines back up until it goes south on you again. Follow that line. If it goes around the back and then forward towards the alternator, that's the one going to the fuel pressure regulator.

 

[Lifted92]

Ok makes sense about the test. I kind of figured I was over looking it. So its not the mass air flow sensor. Its not the fuel pressure regulator I just replaced that 15 minutes ago. I am out of ideas now what it could be.

 

[Roadrunner777]

Test for spark, see if a plug is wet. I'm just trying to go towards fuel or ignition, at this point.

 

[Lifted92]

If the mass air flow passes with proper voltage could it dirty and cause these problems. When I read through the test procedure it did not say anything about what the signal voltage should be at or around. Mine at idle was at 1 volt and increase to 1.62 at half throttle and when I let go of the throttle from half throttle to idle it dropped to .92 volts. The truck started to idle high while I had it running so I checked the signal then as well and it was reading 1.16 volts like the throttle was being opened. Would that be a bad throttle position sensor.

 

[Roadrunner777]

TPS is an easy test:

http://www.explorerforum.com/forums/showthread.php?p=2349296

 

[Lifted92]

i just tested the tps and at normal idle its .92 volts and at wot is 4.62 volts so its not the tps.

 

[Lifted92]

im just lost now. the tps is good the maf is good fpr is new and good, all new vacuum lines. i have no idea what would cause the high idle in park and normal idle in drive. or cause it to fall on its face and stall when trying to accelerate. i also thought it could be the vacuum modulator at the trans i changed that. iac valve is good i tested the ohms on it and its new also. i checked for codes and and came up with a few. 2 where coolant temp sensors codes, 2 where mass air flow codes but i think those came on when i had the truck running with it unplugged, and 1 was for the tps but i think that's and old code from the old tps before being replaced

 

[Roadrunner777]

Can you disconnect the battery for 5 minutes, then rerun the codes? Probably would be good to get a fresh list.

 

[Lifted92]

well i figured it out! bad mass air flow sensor. with me changing everything including the coolant temp sensor iac tps vacuum mod and vacuum lines that was the only thing old haha. i said i have to try it and sure enough as soon as i started it after changing it and instantly the idle was much lower still a couple hundred high like 850 900 over the preferred 700. thanks roadrunner for all the ideas and help and the links for testing everything its very much appreciated.

 

[Roadrunner777]

Glad it worked out. You should disconnect and reconnect the battery, which will cause the computer to relearn idle. You should be good to go.

 

[Lifted92]

Ok I'll do that after dinner haha. Again thanks for all the help.