Bad idle and maf issues...ideas anyone? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Domadred · 03-28-2005, 08:39 PM

Background: s13 blacktop in a 91 240sx. Freshly installed, never driven. Apexi AFC, rb25 maf

Two problems.
Without the maf: The engine tries to start, drops to 200 rpm, and then catchs when I press the gas. It will idle at 850 for about a minute, and then dies unless I keep my foot on the gas. What could be causing this?

-I have taken the intake manifold off and am looking at the aav. How
can you check if it is ok?

With the maf: Car will not idle. I know this is a maf problem. I have searched and havent found any specifc info on afc settings, besides that the rb25 maf is similar to the z32 maf. I have 3 volts coming in to the maf.

-What is the rb25 maf resistance supposed to be?
-Apexi AFC settings for the rb25 maf would be super.

Domadred · 03-30-2005, 12:29 AM

http://www.240sxforums.com/forums/sh...ad.php?t=52992

Does anyone else have suggestions?

drift freaq · 03-30-2005, 01:37 AM

do you have a air filter on that MAF? Believe it or not if you do not it will affect the way maf meters the air and your engine will not idle. If you do not have an air filter on it try putting one on.

Domadred · 04-01-2005, 02:24 AM

Driftfreaq; would the lack of an air filter affect the reading on an afc, before the car was even turned on?

Just tonight, I went back over my wiring...I removed one wire at a time and tested the maf to see if the reading changed. No change. I know I have correct voltages, but are they on the right pins...?

drift freaq · 04-01-2005, 10:13 AM

Quote:

Originally Posted by Domadred

Driftfreaq; would the lack of an air filter affect the reading on an afc, before the car was even turned on?

Just tonight, I went back over my wiring...I removed one wire at a time and tested the maf to see if the reading changed. No change. I know I have correct voltages, but are they on the right pins...?

it should not because the sensor only picks up the air that is passing by it. If the engine is not running their would be no air passing by the sensor. If you have the base voltage readings that the sensor is supposed to have on paper and you tested it and they are the same your back to what I said earlier if you have not installed a air filter. Yes it could be that simple.

SequenceGarage · 04-01-2005, 05:59 PM

I'm assuming you don't have a plug for the mafs.. So you need to figure out what the pinout is supposed to be.

First of all, from the ECU: Black/White = power Black = ground white = signal.

You should be getting 5v in, is your battery really low? Charge your battery man.

S-AFC II Settings should be Hotwire sensor type obviously, with 4in and 6out.

The best way to figure out the pinout for the mafs is to check resistance. There was a post on this on FA about how the guy did it I can't remember exactly what he did but basically he took an S13 mafs and tested the resistance between 2 terminals (A+B, A+C, B+C) The resistances were something like:

5 ohm
10 ohm
30 ohm

for example. Your RB mafs should be somewhat close (low, medium and high resistance basically) Once you know that you can use logic to figure out which wire is which.

lets assume AB = 5 AC = 10 BC = 30

And you Know (From KA mafs of which you have plug) that A = power B = ground C = signal

well then you know AB is power and ground, so the lowest resistance you find on the RB mafs MUST be power and ground, mark each A and B as "Power OR Ground"

now you know AC is power and signal, so mark A and C as "Power OR Signal"

OH SHIT! Now you KNOW A has to be Power, therefore B HAS to be Ground, leaving C as signal.

Bam.

Domadred · 04-07-2005, 01:55 AM

Quote:

Originally Posted by SequenceGarage

I'm assuming you don't have a plug for the mafs.. So you need to figure out what the pinout is supposed to be.

First of all, from the ECU: Black/White = power Black = ground white = signal.

I do have the plug for the rb maf. The wires coming out of the harness are not whiteblack, black, and white. That is part of the problem!

I have a large black wire, and in a seperately sheathed wire, I have: green, black, red and white. Green and black were 3 volts, red and white were 12 volts.

Quote:

Originally Posted by SequenceGarage

You should be getting 5v in, is your battery really low? Charge your battery man.

S-AFC II Settings should be Hotwire sensor type obviously, with 4in and 6out.

My battery may be running low, but not THAT low... Shouldnt the AFC settings be flipped? 6in and 4out. Thereby reducing the voltage the ECU receives?

Correct me if I am wrong, but with A-B reading 5, B-C reading 2, and A-C reading 10.

As you look into the plug, the correct wires would be:
ground on the right most maf pin
power on the middle maf pin
signal on the left most maf pin

Mine was wired as:
power on the right most maf pin
signal on the middle maf pin
ground on the left most pin

the head · 04-07-2005, 08:57 AM

the 4 and 6 are not voltages they are internal settings that tell the SAFC what MAF is on the car and what MAF the ECU needs to be fed then translates the two

drew935 · 04-21-2005, 02:11 PM

I have a stock DE with an HKS filter on it. This has happened to me several times but now I want to fix the problem and not just bandage it. I'll be driving and all of a sudden power dies. No check engine light right now. But I did check the codes and the maf came up. So far I have sprayed carb cleaner to get it to run again and then wait a couple of minutes and it's back to normal...

Is my filter the cause of this happening.>?

I have only a Super Mega Flow filter, and z32 fuel filter for the mods that would affect this. I'll be checking the voltage on the maf soon. Should I cap off the egr and any other valves not needed to help remedy this? Or is there something else I should be looking at? I just had a smog last month and it came up super clean...

drew935 · 04-25-2005, 04:40 PM

bump...any help for me

03-28-2005, 08:39 PM	#1
Domadred Join Date: Mar 2005 Location: Las Vegas Posts: 5 Trader Rating: (0) Feedback Score: 0 reviews	Bad idle and maf issues...ideas anyone? Background: s13 blacktop in a 91 240sx. Freshly installed, never driven. Apexi AFC, rb25 maf Two problems. Without the maf: The engine tries to start, drops to 200 rpm, and then catchs when I press the gas. It will idle at 850 for about a minute, and then dies unless I keep my foot on the gas. What could be causing this? -I have taken the intake manifold off and am looking at the aav. How can you check if it is ok? With the maf: Car will not idle. I know this is a maf problem. I have searched and havent found any specifc info on afc settings, besides that the rb25 maf is similar to the z32 maf. I have 3 volts coming in to the maf. -What is the rb25 maf resistance supposed to be? -Apexi AFC settings for the rb25 maf would be super. Last edited by Domadred; 03-28-2005 at 09:24 PM..

03-30-2005, 01:37 AM	#3
drift freaq R.I.P. Aya, always love Join Date: Nov 2001 Location: Los Feliz/Hollywood Posts: 18,558 Trader Rating: (215) Rides Gallery: drift freaq Feedback Score: 215 reviews	do you have a air filter on that MAF? Believe it or not if you do not it will affect the way maf meters the air and your engine will not idle. If you do not have an air filter on it try putting one on. __________________ "Having a lot of tracks on a song is like putting stickers on a car to get more horsepower" New Video https://www.youtube.com/watch?v=uebV1OnbRsw Buy my mounts! http://zilvia.net/f/sale-items/51531...ns-mounts.html http://zilvia.net/f/tech-talk/317539...e-mouts-6.html

04-01-2005, 05:59 PM	#6
SequenceGarage Leaky Injector Join Date: Mar 2005 Location: Toronto, Ontario, Canada Age: 35 Posts: 82 Trader Rating: (0) Feedback Score: 0 reviews	I'm assuming you don't have a plug for the mafs.. So you need to figure out what the pinout is supposed to be. First of all, from the ECU: Black/White = power Black = ground white = signal. You should be getting 5v in, is your battery really low? Charge your battery man. S-AFC II Settings should be Hotwire sensor type obviously, with 4in and 6out. The best way to figure out the pinout for the mafs is to check resistance. There was a post on this on FA about how the guy did it I can't remember exactly what he did but basically he took an S13 mafs and tested the resistance between 2 terminals (A+B, A+C, B+C) The resistances were something like: 5 ohm 10 ohm 30 ohm for example. Your RB mafs should be somewhat close (low, medium and high resistance basically) Once you know that you can use logic to figure out which wire is which. lets assume AB = 5 AC = 10 BC = 30 And you Know (From KA mafs of which you have plug) that A = power B = ground C = signal well then you know AB is power and ground, so the lowest resistance you find on the RB mafs MUST be power and ground, mark each A and B as "Power OR Ground" now you know AC is power and signal, so mark A and C as "Power OR Signal" OH SHIT! Now you KNOW A has to be Power, therefore B HAS to be Ground, leaving C as signal. Bam. __________________ Sasha Anis Sequence-Garage

04-07-2005, 08:57 AM	#8
the head Nissanaholic! Join Date: Jul 2002 Location: in a dark room mastering the art of typing with one hand Posts: 2,164 Trader Rating: (3) Feedback Score: 3 reviews	the 4 and 6 are not voltages they are internal settings that tell the SAFC what MAF is on the car and what MAF the ECU needs to be fed then translates the two __________________ I never knew you could do that with an eggplant

04-21-2005, 02:11 PM	#9
drew935 Zilvia Addict Join Date: Nov 2003 Location: Silver Creek - San Jose Posts: 996 Trader Rating: (0) Feedback Score: 0 reviews	I have a stock DE with an HKS filter on it. This has happened to me several times but now I want to fix the problem and not just bandage it. I'll be driving and all of a sudden power dies. No check engine light right now. But I did check the codes and the maf came up. So far I have sprayed carb cleaner to get it to run again and then wait a couple of minutes and it's back to normal... Is my filter the cause of this happening.>? I have only a Super Mega Flow filter, and z32 fuel filter for the mods that would affect this. I'll be checking the voltage on the maf soon. Should I cap off the egr and any other valves not needed to help remedy this? Or is there something else I should be looking at? I just had a smog last month and it came up super clean... __________________ I'm driving fast -drew

03-30-2005, 12:29 AM	#2
Domadred Join Date: Mar 2005 Location: Las Vegas Posts: 5 Trader Rating: (0) Feedback Score: 0 reviews	http://www.240sxforums.com/forums/sh...ad.php?t=52992 Does anyone else have suggestions?

04-01-2005, 02:24 AM	#4
Domadred Join Date: Mar 2005 Location: Las Vegas Posts: 5 Trader Rating: (0) Feedback Score: 0 reviews	Driftfreaq; would the lack of an air filter affect the reading on an afc, before the car was even turned on? Just tonight, I went back over my wiring...I removed one wire at a time and tested the maf to see if the reading changed. No change. I know I have correct voltages, but are they on the right pins...?

04-25-2005, 04:40 PM	#10
drew935 Zilvia Addict Join Date: Nov 2003 Location: Silver Creek - San Jose Posts: 996 Trader Rating: (0) Feedback Score: 0 reviews	bump...any help for me __________________ I'm driving fast -drew

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