MAF sensor extension goes horribly wrong

[Nismo180]

Okay, I had just got my SR20 going. Everything was working fine but the motor refused to rev higher than about 2.5k at part throttle and 3k underboost. So I investigated the MAF extension. It turns out my buddy who extended it for me doesn't know much about wiring and it was shorting out in there somewhere. When I pulled off all the tape, there were exposed wires at every connection. I'm like CRAP! and went and turned off the key and then took of the negative battery cable. Yeah, too late. Getting no power to the line you tap your S-AFC into pin 36 I believe. I check all my fuses and the 25a brown one in the main box labeled FL 25A ENG CONT. Was blown, put in a new one and nothing changed. When I turn the key to on, EVERYTHING works except for my S-AFC, and my fuel pump doesn't click on. I can't find any other fuses in the car that don't work except for one under the dash labeled ST. Signal. But, I don't think that is anything important.

The engine will turn over, all the accesories work, but I can't hear the fuel pump when I click it to on and it's a Walboro so I'm fairly certain it isnt' clicking on because I could hear it big time before.

I haven't checked any of the relays yet... How do I do that, and any other ideas besides that?

[projectRDM]

Why did he extend the wires in the first place? The SR harness comes with enough lead unless you moved it down in the fender well.

Pull and test the relay plugs for power/signal (download the FSM) and then double check all the fuses again. If the signal is dead then you've blown a trace in the ECU.

[Nismo180]

Ummm... there was no way that harness was going to make it all the way over to the MAF. Anyway, went and jacked some new EGI and EGI pump relays from my buddies old shell. When I plugged them in the ECU willl now turn on, and the car will run, but it'll idle high for a while, then drop down and try to idle at like 500rpm(might be my timing) But, the big problem I think is still in the relays. The EGI pump relay only has power going to it when the key is clicked on. I pulled off the relay and tested the leads. The EGI one, is power on all the time, key on or off. Is that normal?

[mrmephistopheles]

FYI, when extending MAF wires (on any car): Solder and shrink-tube, and wrap connection with electrical tape. Butt-splicing doesn't cut the mustard.

[Nismo180]

FYI, when extending MAF wires (on any car): Solder and shrink-tube, and wrap connection with electrical tape. Butt-splicing doesn't cut the mustard.


Yeah, duh seems that was explained in the first two sentences of the post. EVERY other wiring mod in all of the re-wiring was done with solder and shrink tubing. Now then, let's act like good little moderators and not bother posting unless it contributes.

I believe I've got a bit of a lead, I took the test light to my buddies Silvia and some of the hot leads were not the same so I'll be checking that out tomorrow. Until then, anyone know any other reason the ECU would remain on even when the ignition is off? Of, FYI there was a red light on inside the ECU, that I don't recall being visible when it was running right.

[projectRDM]

Ummm... there was no way that harness was going to make it all the way over to the MAF.

In five SR installs I've never extended a single wire on the harness. Everything will reach all day if you skin it back far enough.

Verify the relay schematics in the FSM to ensure you're seeing everything you should.

[Nismo180]

In five SR installs I've never extended a single wire on the harness. Everything will reach all day if you skin it back far enough.

Verify the relay schematics in the FSM to ensure you're seeing everything you should.

I've been looking at it and the relays I see the power going through are labeled stuff I haven't seen under the hood. schematic says ECCS, I have no idea where that is.

[sdtouge]

another thing to note, some sensors on the harness use shielded wire, the knock sensor, and the mafs use it, all it is is a normal wire, then it sorta has another wire around it, to "shield" it from picking up other signals. it is usualyl grey and can be found alot in your old ka harness.

try to use that if you need to rewire or extend anything that uses that in the first place.

[Nismo180]

another thing to note, some sensors on the harness use shielded wire, the knock sensor, and the mafs use it, all it is is a normal wire, then it sorta has another wire around it, to "shield" it from picking up other signals. it is usualyl grey and can be found alot in your old ka harness.

try to use that if you need to rewire or extend anything that uses that in the first place.


I used video shilded wiring for it so, yeah same difference.

[mrmephistopheles]

Now then, let's act like good little moderators and not bother posting unless it contributes.


Nice attitude. Note to you: my post, being informational, is contributing.
Also, FYI:
Okay, I had just got my SR20 going. Everything was working fine but the motor refused to rev higher than about 2.5k at part throttle and 3k underboost.
I see nothing relating to; 1. MAFS, 2. Soldering, 3. Shrink tubing.
Those are the first two sentences of your post in which you claim it was explained.
Final note: Get your fucking facts straight, brush that fucking chip off your shoulder and build a bridge to get over the fact that I'm just trying to help. If you WANT me to be an asshole to you, it's no problem, just keep it up with the attitude. I'm not in this game to be an asshole, I'm in it because I like 240sx's and I like helping others.
Now then, if you'd like me to be a nice guy, just be nice to me. I can take constructive criticism and freely admit my mistakes.

-Kevin

[nismo2491]

dude, you've been in the 240sx scene for like 5 minutes. wtf is with being all mr big and bad getting smart with people who obviously know more than you because their sr swaps all worked right.

and btw I've been here since 2001 so don't try to play the game that I'm new too.

[the head]

test your MAF signal voltage as said above if you get nothing you toasted your ecu

seriously I think this is the dumbest SR install mistake I have ever heard of on this board