SR swap runs nicely for 3 seconds, then dies... violently.

[ctnewman]

I have an SR car that i did not swap. It used to run fairly well, then in about a 20 minute period it went from OK, to bad, to DEAD.

Specs:
s13 coupe
s13 redtop
s13 ECU
DOHC mafs
SAFC set to 05/06, no other changes
The wiring on the car is not the best.
The mafs wire is NOT shielded

Symptoms:
Car starts. Idles alright. Not awesome, but fairly smooth
If you stab the gas, it will rev for a little bit, then just die.
If you hold the throttle consistently at about 5% it will rev to about 2000-2500 sit there, perfectly smooth for 1... 2... 3... then just fall flat on it's face with NO change in input. It doesn't start to stumble, it just DIES. Like someone flipped a switch. Then the revs will obviously drop and then the motor shakes, shudders and stalls. This occurs with the mafs plugged in, or disconnected, but the engine sounds/feels different each time.

What it's not:
I tried a different ignitor chip, no help
I tried new spark plugs, no help


Some thoughts:
-I am trying to get my hands on another DOHC mafs. I don't think that's it, but it's worth a try. I also have a 300zx mafs, but do not have the pigtails for it.
-I'm wondering if the problem occurs when the computer switches to closed loop, though i don't know how quickley it would do that... Can i just unplug the O2 sensor to lock it in open loop?
-Shit ECU?



Can anyone else perhaps shed some light on this here? I have very little free time to fuck around with this car. Once i solve the problem, I am going to sell it.

Thanks!

[projekt_s13]

iirc sr's use the SOHC maf not the DOHC

[ctnewman]

iirc sr's use the SOHC maf not the DOHC

correct, hence the SAFC being used with the 05 -> 06 MAFS correction

[unicoladron]

1. the MAF signal wire is shielded for a reason. the maf signal is very sensitive and there is all types of wierd magnetic signals in the engine bay.
2. i had my o2 sensor unplugged for a while and it seemed to run just fine. check your o2 sensor wiring too, i experienced the same problem because my o2 sensor wiring was phucked.
3. there are tons of z32 MAF wiring guides out there.
4. disable your AFC for troubleshooting purposes to eliminate that.

you need to sheild your MAF wiring, nissan did this from the factory fora reason. when i rewired my harness, it seemed to be the same material as CAT5 network cable shielding. but i didn't use that, i used the shielding from the KA harness.

and yes, your car WILL run like shit if you don't sheild your MAF wire, i've seen it.

also i've seen that metal wrapping material inside of the maf sheilding cause a short; make sure there isn't a short.

[ctnewman]

1. the MAF signal wire is shielded for a reason. the maf signal is very sensitive and there is all types of wierd magnetic signals in the engine bay.
2. i had my o2 sensor unplugged for a while and it seemed to run just fine. check your o2 sensor wiring too, i experienced the same problem because my o2 sensor wiring was phucked.
3. there are tons of z32 MAF wiring guides out there.
4. disable your AFC for troubleshooting purposes to eliminate that.

you need to sheild your MAF wiring, nissan did this from the factory fora reason. when i rewired my harness, it seemed to be the same material as CAT5 network cable shielding. but i didn't use that, i used the shielding from the KA harness.

and yes, your car WILL run like shit if you don't sheild your MAF wire, i've seen it.

also i've seen that metal wrapping material inside of the maf sheilding cause a short; make sure there isn't a short.


Yeah, i was thinking about shielding it. Please know that I did NOT do the swap. I bought the car fairly cheap with the intention of flipping it, but then it shit on me. The wiring is all soldered, but not great. The ignitor is in the passenger compartment. WEIRD. I have ton of old engine harnesses, I was planning on liberating some shielded cable from there.

I also tried putting a fuel pressure gauge on it, to see if the pump was shitting on me, but it held pressure and didn't fall off.

[unicoladron]

also if the ignitor chip was moved in the cabin, check the quality of all of that wiring too. if this jagoff did his own soldering, perhaps there is a short somewhere else due to neglect to use proper heat sshrinking techniques, or ghetto style couplers, or even just electrical tape. which kind of explains that it ran ok for a while, but recently started shitting the bed.

[ctnewman]

Yeah... it just boggles ,e that it will run great for a few seconds, then just DIE. It's not like i'm driving it or wiggling wires.

[TUnity2]

check all your wiring. and also, i know it sounds crazy, but if the car was once auto check the relays, even the ones you think you dont use. my second sr swap wouldnt run until i installed the brown relay.

[steve shadows]

correct, hence the SAFC being used with the 05 -> 06 MAFS correction

uh...

its a sohc maf?

it needs to be 2 in 6 out for z maf


i believe the stock settings for sohc ka/stock sr maf are 6 in and 6 out

[ctnewman]

uh...

its a sohc maf?

it needs to be 2 in 6 out for z maf


i believe the stock settings for sohc ka/stock sr maf are 6 in and 6 out

it's a DOHC maf

[steve shadows]

it's a DOHC maf

why?

:duh:

use a sr/single cam maf make yoru life easier or just go z32

[ctnewman]

why?

:duh:

use a sr/single cam maf make yoru life easier or just go z32

it was on the car when i got it. trying to get a hold of a z32 mafs pigtail (i have the sensor) or a just a SOCH mafs

[ctnewman]

for those interested:

the maf in the car WAS a SOHC maf, but for some reason, the previous owner still had a maf correction factor on the car. This explains why it ran so damn rich all the time previously.

I replaced the SOHC with a new SOHC maf, zerod out the SAFC and viola, it works, better than it ever did!