How to test MAF to see if it's working?

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pumpiniron
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How to test MAF to see if it's working?

Postby pumpiniron » Sat May 05, 2007 8:00 pm

I think my SR20DET has a bad MAF but before I go out and buy a new one I was wondering if anyone knows how to test a MAF to see if it's bad? I have a multimeter so perhaps someone knows the voltage I should be checking the MAF for or something? A step by step walkthrough would be awesome since I've never done this before (but yes I have used a multimeter before many times!).

Also does any other MAF cross refference with the SR20DET MAF?


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Steve Lloyd
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Re: How to test MAF to see if it's working? (pumpiniron)

Postby Steve Lloyd » Sun May 06, 2007 4:14 am

what is your car doing to lead you to believe your MAF is bad?? First thing i would do as far as testing goes is make sure you have continuity between MAF and ECU. This will rule out the wiring for you.

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S13FASTBACKSR
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Re: How to test MAF to see if it's working? (Steve Lloyd)

Postby S13FASTBACKSR » Sun May 06, 2007 6:20 am

MAF voltage should be 12v on the power wire (black and white wire) and 5v on the signal wire (white wire) the all black wire is the ground. Another way to test the MAF to see if its bad is to check for codes on the ecu..if you get a code 12 then your MAF is indeed bad

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Re: How to test MAF to see if it's working? (Steve Lloyd)

Postby pumpiniron » Sun May 06, 2007 8:26 am

Steve Lloyd wrote:what is your car doing to lead you to believe your MAF is bad?? First thing i would do as far as testing goes is make sure you have continuity between MAF and ECU. This will rule out the wiring for you.
Well... When you start the car up it idles incredibly rough at about 2k rpms and then after idling extremely rough for about 15 seconds it drops down to 1k rpms, idles rough still and sputters until it dies. You can smell a TON of unburnt fuel coming out the exhaust (I mean a ton!). The weird thing is if you try to give it some gas by pressing on the throttle it won't give it any gas at all at first but after holding your foot on the pedal for about 30 seconds it will jump up to about 5k rpms but it sounds like it's missing or sputting even at 5k rpms!

Any ideas about what that might be?

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adrianfromthecastle
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Re: How to test MAF to see if it's working? (pumpiniron)

Postby adrianfromthecastle » Sun May 06, 2007 8:36 am

what I did to check my mafs is to unplug it while is was idling like sh*t.

When I unplugged my mafs while it was idling @ 400-500 rpm, it corrected itself and started idling at 700-800 like its supposed to. I plugged it back in, then it started idling like sh*t again...

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S13FASTBACKSR
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Re: How to test MAF to see if it's working? (adrians_s13)

Postby S13FASTBACKSR » Sun May 06, 2007 9:07 am

your running extremely too rich then...heres what you should do first..check the voltages first and let us know what they come out at..even if they come out at what i said they should be go on to the next test..unplug your maf see if it revs any better and see if it will rev past 2500rpm (because unplugged it shouldnt) then clean the maf with a can of electronic spray cleaner. Spray the thermosister inside of the maf but dont touch it..if this is dirty this will cause your MAF to not function properly..now if you engine does not run properly after that then turn the key on and notice on the back of the ecu there will be a l.e.d. that will be on..now start the engine and let me know if the l.e.d. stays on or goes off

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Re: How to test MAF to see if it's working? (S13FASTBACKSR)

Postby pumpiniron » Sun May 06, 2007 9:48 am

Oh here is what I can tell you so far... Unplugged the MAF while running and the car doesn't run any different at all with the MAF unplugged, it still runs the EXACT same with the MAF unplugged it just wont rev past 2500rpm. Anyhow I got out the multimeter and measured the current on the TPS and I found this... The TPS has 5v even while the car is just idling at 900rpm. I then proceeded to unplug the TPS and surely enough the car runs the EXACT same without the TPS plugged in.

I'll go check the light on the ECU now and let you know what I find!

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S13FASTBACKSR
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Re: How to test MAF to see if it's working? (pumpiniron)

Postby S13FASTBACKSR » Sun May 06, 2007 10:01 am

hmmm tps is definately off..should only be 5v at w.o.t....acutually should only be 4.5v at w.o.t. adjust your tps to .45v to .55v at idle and let us know how the car runs then

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Re: How to test MAF to see if it's working? (S13FASTBACKSR)

Postby pumpiniron » Sun May 06, 2007 10:17 am

S13FASTBACKSR wrote:hmmm tps is definately off..should only be 5v at w.o.t....acutually should only be 4.5v at w.o.t. adjust your tps to .45v to .55v at idle and let us know how the car runs then
How do I adjust the TPS to that? I mean I know and can reposition it a little but what does that have to do with changing the voltage?

If I remember right I think I can use a TPS sensor off of a Sentra SE-R correct?

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S13FASTBACKSR
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Re: How to test MAF to see if it's working? (pumpiniron)

Postby S13FASTBACKSR » Sun May 06, 2007 10:21 am

by repositioning it that changes the voltage..if you take the tps off and look at the lever on the back you will notice its spring loaded..you dont even have to take it off to see that..you can just push the lever up and down..it works in motion with the TB flap. When the that flap opens there is more air going in to the engine so the voltage goes up to allow more fuel into the engine. you running so rich and smelling so much unburnt fuel most likely because the TPS voltage is reading above what it ever should read..half a volt higer than w.o.t. so your pretty much getting max amount of fuel at idle..loosen the 2 screws and turn the tps down iirc..maybe up..you can figure that part out..and let us know what happens when you get it to .45-.55 volts at idle..also did you check your ecu?

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Re: How to test MAF to see if it's working? (S13FASTBACKSR)

Postby pumpiniron » Sun May 06, 2007 10:36 am

Ok I tried that with the TPS but the voltage never changes. It remains at 5v the entire time no matter which way I turn it.

I'm assuming to see this LED I will have to take out the ECU or something because I can't see it where it's sitting right now...

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S13FASTBACKSR
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Re: How to test MAF to see if it's working? (pumpiniron)

Postby S13FASTBACKSR » Sun May 06, 2007 10:49 am

first of all if your tps voltage doesnt change especially if you dramatically change its position then its bad..a 1995 ka24de sensor will do the trick. but when you go to the autoparts store bring your current tps and try to purchase one with a picture in their computer next to its description and very carefully observe the lever..when i replaced my tps i thought i had gotten the right one but the lever was at a different angle..secondly to see the ecu's l.e.d. you must obviously remove the kick panel and then any bolts that may be holding the ecu to the inside of the car..then let it hang and turn it around and you should be able to see it

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Re: How to test MAF to see if it's working? (S13FASTBACKSR)

Postby pumpiniron » Sun May 06, 2007 1:55 pm

Ok so what you're saying is that not just any 95 KA24DE TPS sensor will work?

Does the one from the Sentra SE-R work because it sure looks like it would?

Also one last thing. With the ECU light is it supposed to go off after the car starts and if it doesn't go off what does that mean?

From the looks of things it seems like my TPS is bad. The voltage remains the same no matter how far open or closed the TPS goes and all that unburnt fuel coming out the exhaust would make sense if it is indeed the TPS. God I fear how much a new TPS sensor will cost...

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Re: How to test MAF to see if it's working? (pumpiniron)

Postby pumpiniron » Sun May 06, 2007 1:55 pm

Oh one more thing... Does the 95 KA24DE TPS plug right up or does it require cutting and splicing to a new connector?

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Postby SpeedRacer1 » Sun May 06, 2007 2:00 pm

If you have a 1991-1996 S13 SR20DET you want the TPS from a Sentra SER/NX2000.Part number 22620-53J01.

The connector needed to go into the TPS is a 3 wire connector. If you do not have it you will need to find one and splice the subharness coming off your engine harness into the pigtail off the TPS.

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Re: How to test MAF to see if it's working? (pumpiniron)

Postby S13FASTBACKSR » Sun May 06, 2007 2:00 pm

not just 95 but any s14 ka and dont fear the price its not more than 100 bucks and its worth it to get your engine running correctly...I cant say for sure about the se-r tps..did you search and read that? I cant remember exactly what tps i went with for all i know i may have heard the same thing and went with it but like i said i cant be to sure..i dont know if i went with the s14 ka or not lol my memory is not too good but im pretty sure i didnt have to solder any wires it was just plug and play

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Re: (SpeedRacer1)

Postby pumpiniron » Sun May 06, 2007 2:01 pm

You the man! Thanks for the info. The sentra SE-R one looks exactly like what I need judging from the pics! The connector on it looks like it should plug right in as well because the plug on the engine harness for the TPS has 3 wires so I'm assuming that means the harness is meant for a manual transmission car?

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Re: How to test MAF to see if it's working? (S13FASTBACKSR)

Postby SpeedRacer1 » Sun May 06, 2007 2:06 pm

S13FASTBACKSR wrote:not just 95 but any s14 ka and dont fear the price its not more than 100 bucks and its worth it to get your engine running correctly...I cant say for sure about the se-r tps..did you search and read that? I cant remember exactly what tps i went with for all i know i may have heard the same thing and went with it but like i said i cant be to sure..i dont know if i went with the s14 ka or not lol my memory is not too good but im pretty sure i didnt have to solder any wires it was just plug and play
No, I looked it up in the Japanese Nissan Parts Dept program, then crossreferenced the part with the US Nissan Parts Dept program. Should be about $89 new so I would try to get one at a junkyard.

The connector to the TPS should be brown.

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Re: How to test MAF to see if it's working? (SpeedRacer1)

Postby S13FASTBACKSR » Sun May 06, 2007 2:07 pm

i was wondering how you found this part number..also speed racer why does it say ka in the sr parts list? I guess because it works but needs soldering

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Re: How to test MAF to see if it's working? (SpeedRacer1)

Postby pumpiniron » Sun May 06, 2007 2:09 pm

Good luck on finding a SE-R at any junkyard around here... Seriously. I looked at my local auto parts stores and they range from $75 - $120 depending on if you want OEM or not. Looks like I'm just going to have to bite the bullet and get a new one. I'll let you guys know how it turns out.

Oh by the way no one ever answered the question I had about the ECU light. Is it supposed to go on or stay off or what? What does the light even mean?

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Postby SpeedRacer1 » Sun May 06, 2007 2:10 pm

Because I didnt make that part of the list. Chances are it will work fine and give the right voltage, but its not the exact replacement.

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Re: How to test MAF to see if it's working? (S13FASTBACKSR)

Postby pumpiniron » Sun May 06, 2007 2:10 pm

S13FASTBACKSR wrote:i was wondering how you found this part number..also speed racer why does it say ka in the sr parts list? I guess because it works but needs soldering
Exactly. It works but it needs soldering. I've found a lot of parts in the parts list work but require small modifications. I've taken a look at numerous pictures of the SE-R TPS sensor and it looks like it will fit perfect with no mods at all. Even the plug on it is identical to the one coming off my engine harness!

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Re: How to test MAF to see if it's working? (pumpiniron)

Postby S13FASTBACKSR » Sun May 06, 2007 2:22 pm

ya bro just bite the bullet it will definately be worth it..think of it like this..75 dollars or 300..75 aint that bad at all..more serious stuff good happen so it being just the tps is kinda lucky..by the way about the ecu..when the key is in the on position the light is supposed to stay constantly lit up..when the engine is started that light should go off and if it doesnt go off then your ecu is bad..thats why i wanted you to do that because it wouldve told us if the ecu is bad or not

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Postby SpeedRacer1 » Sun May 06, 2007 2:24 pm

For a used TPS call up Feltons in WA and see if they have and/or will ship one to you. http://www.feltonautoparts.com/

The light on the ECU stays on all the time. When you turn the screw counterclockwise the ECU goes into diagnostic mode and blinks. The number of long and short blinks represent the codes being thrown. Generally a healty Nissan ECU should throw a code 55, 5 long blinks followed by 5 short blinks.

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Re: (SpeedRacer1)

Postby S13FASTBACKSR » Sun May 06, 2007 2:27 pm

hmmm dont want to arouse an argument but I read back when i was having engine problems that if your ecu's l.e.d. stays on while the engine is running then the ecu is bad..its like the ecu's code..instead of a flashing sequence it will just stay on..so i went out and did this test and sure enough it stayed on so i ordered another ecu and that ecu's l.e.d. went off and the engine ran great

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Postby SpeedRacer1 » Sun May 06, 2007 2:39 pm

I just went to double check, with the engine off, key on ignition the light stays off in regular mode, in diagnostic it flashes codes. You can start the engine in either regular or diagnostic and it will run fine in either mode but the light turns off completely.

Whenever I have seen ECU's go bad, they will flash the code for the circuit that fried.

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Re: (SpeedRacer1)

Postby S13FASTBACKSR » Sun May 06, 2007 2:43 pm

all i can say is IDK..thats wierd though because I speak from what I've experienced and so do you

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Re: (S13FASTBACKSR)

Postby pumpiniron » Sun May 06, 2007 4:18 pm

Ok so I checked out the light on the ECU and when you turn the car on it goes off. I also tried turning it to diagnostic mode and even with the TPS sensor unplugged it doesn't blink or anything like that at all?

Also something else I noticed is that several wires to my ECU have been cut and don't seem to have a corresponding wire that they go to. Namely an orange/black wire, green/black wire, blue wire, and a few others. I checked the ECU pinout diagram and one of them is the EGR solenoid valve control wire, the other is an ambient air temp sensor, and the other one is a TX data (signal to Nissan Consult hand terminal) wire, and the other seems to be a Chk start wire or something... Not sure if any of these are even needed but I wonder why they were cut none the less. Also the little white plug coming off the ECU harness for the diagnostic tool has several cut wires as well. Is any of this normal?

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Postby SpeedRacer1 » Mon May 07, 2007 2:59 pm

The extra wires are normal on every swap. One is AC, which if you decide to use AC you will eventually need to patch that circuit.

The Nissan consult wires (TX,RX,CHK) are only needed if you want to try to hook up the consult port. And the rest are pretty much useless.

The light only flashes with the engine off and key in on position, if its not flashing during that you may have an ECU issue too.

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Re: (SpeedRacer1)

Postby pumpiniron » Mon May 07, 2007 3:53 pm

So if the ECU is health and it's not throwing any codes then how many times is it supposed to Flash?


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