S13 SR20DET starts but only idles with MAF off

[Super Ertoy]

My friend has an S13 redtop and everything is wired in correctly. checked FSM for multimeter readings and everything shows to be good but when starting it will not idle. Blubbers like a dying walrus for a couple of seconds. But when we unplug stock SR MAF it idles just fine! what can cause this problem?

we have tried swapping MAFs from known working SR but same results. could it possibly be an ECU problem? stock SR ECU btw.

Let me know if you have any ideas.

[cotbu]

Pull codes, check Inside the ecu for: 1. Daughter board.
2. Burnt traces, pins.
3. Smells.

Then do a continuity test on the wires for the mafs. There should be a solid tone, while fiddling with the wires.

Sent from my Highly Tuned Vibrant!!!

[Super Ertoy]

so we checked for codes and came out with 55 - no issues. stock SR ecu so no daughterboard or chips. nothing burnt nothing broken. we put the ECU in a working S13 SR20 and it ran like shit at first but after turning off the ignition and trying again it was fine.

wires on the maf are all good its all as should be according to FSM. cant figure it out.

[wangan_cruiser]

can you explain the meaning of "wires are good".

how did you test it?

[ged1221]

Check maf sensor!!!

[Johannes]

When the MAF is unplugged, the idle is fine, but of course, because of the MAF being unplugged, the RPM would get limited. However, when MAF is plugged back in, it hesitates to idle and most of the time it doesn't respond when throttle is opened.

Here's a couple things I've/We've done:

1. 04/16/2012 : I borrowed a friends SR MAF to see if my MAF was broken, it acted the same so I'm sure my MAF is working. I even tried mine in his SR, and it worked fine.
2. 04/16/2012 : I checked for continuity from the white wire on the MAF and pin #16 on the ECU (Mass Air Flow Sensor Signal Input) - continuity existed.
3. 04/16/2012 : I also check continuity from the black wire on the MAF and pin #17 on the ECU (Mass Air Flow Sensor Ground) - continuity existed.

Now, I thought my ECU was just f'ed up cause I got it from someone else, so I went to my friends with my ECU and plugged it in his SR.

Here's what happened; First start-up in his SR with my ECU in it acted the same as when I had it in my car. We decided to turn it off. The next start-up started normally, idled normally, and revv'ed up normally. Three or more re-starts later, it's still acting normal. Then I thought to myself, "Maybe the ECU got restarted from "my friends" motor?"

So I went home and tried my ECU again, and bahm, it's still the same!
I just re-checked the continuity and resistance again today between the ECU pins and the MAF plug and it came to 0.01 ohms for both white and black wires. I even checked for Black to chassis and it gave me continuity.

I also checked for any ECU codes today and I ended up with a 55 code with the MAF plugged. So what I did was ran the motor for a min or so with MAF UNPLUGGED and turned it off, and checked for codes again, and the MAF code came up, plugged the MAF pigtail back, started the car, checked the codes, and it showed a 55 code (which is normal / no problems)

Ohh I also checked for the B/W wire and I had battery (12v or so) voltage.

Here's a video I took from today;

SR20DET Weird MAF / Idle Problem - YouTube (http://youtu.be/WO1-1b2c_sE)

[Super Ertoy]

Johannes you noob. I posted this for you. This is your car. but you can take the thread from here

[wangan_cruiser]

did you try to check for continuity between black and white wire and see if continuity exist too? if continuity do exist when you do that then you simply have a short

[Johannes]

Yeah I just did.
I checked all three wires for continuity between them and continuity didn't exist in any wires. However, when I checked for low resistance, the B/W 12v with the B wire came up to have 0.00860 or so resistance. But when I checked for the same wires on the CAS harness, the resistance between the B/W wire and the ground wire on there had the same resistance as the one I checked for the MAF. Hmmmmm...

Could low octane and about 3 months old gas affect this much? But it still runs fine without MAF though.

[Johannes]

Anyone else have ideas? =\

[Davidmic747]

at least yours starts -_-

[fliprayzin240sx]

I vote the MAF wiring...double check it, might be grounding out to each other or cross something up. I'd peel that whole thing back and inspect it from tip to tip.

[Johannes]

Yeah I quadrupled check the wiring for the MAF. I even seperated it from the other wires. I have it all the way seperated til the ECU plug. I checked for shorts and didn't get any.

[Super Ertoy]

Close thread. I figured it out this afternoon. He had his MAF backwards. i.e. Filter was on inlet side of maf.