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

NYSpeed Automotive
1

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 quickly 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!

2

it’s because that swap is cursed, spoken from experience.

i would try garlacks (sp) junkyard in niagara falls if you need the pigtails for the maf… they had all sorts of random parts i needed for that swap initially. could be the maf, that DOHC maf was suspect from the start to even be used if it is the same one.

also i thought the ecu used for that was NOT an s13 ecu, but fuck if I could remember I bought about 5 ecu’s for that shit over time. what is the code on it?

edit: also, dunno if ryan did the wiring or if he had someone else do it… always a possibility you have a bad connection somewhere ?

3

i’m still thinking MAF… i know you have the correction in the AFC to run the DOHC maf, but it couldn’t hurt to throw a SOHC maf in there without the afc just as a test to see if it runs correctly or not that way.

4

ya, that and they are easy to find, either that or just borrow one from somebody on here… there are plenty of s13’s laying around

5

is the plug the same?

also, my maf wire is NOT shielded… should i rewire that bitch?

6

newman why do you think its NOT the maf? that’s the first thing i thought of

7

i’m not sure. I just have a feeling it’s not. It’s simple to try, though… hoping jay has one.

8

Depends what the wire goes near. Shielding couldn’t hurt but without seeing where it runs it’s hard to say if it would help.

In my mind when you say the wiring is so so, I’d be testing all the wiring first, espcially the ones the previous owner added related to the s-afc.

9

The only thing that makes me think it’s not wiring is that it’s not something that happens randomly. I did notice that the tach wire was ripped out of the ecu, so i reconnected it and it made NO difference… weird…

The maf wire is within 4 inches of the rear coilpack. The ignitor is RIGHT next to the ECU… i wonder if that’s a problem.

10

<- Has that MAFS. Let me know when you want it :tup:

11

I thought the car was fine and now it barely runs. If the MAF is shorted or the MAF wiring pulled out of a shoddy connection will have the same result. I’d just check the wiring before replacing parts.

12

yeah. i need to dig up the pinout for the ECU…

but swapping a maf takes like 30 seconds.

13

im gonna go with a ground issue here…

14

fuel filter?

15

pressure after the filter is good.

16

newman…

i may be wrong here… but a DOHC mafs is not used on an SR… the SOHC mafs is.

take your SAFC off the car and switch to an SOHC mafs. the voltage is different.

i just called Chris and confirmed that DOHC doesnt work… you may be compensating with the SAFC, but rip both out,. go with SOHC mafs… if it works then put the SAFC back on.

17

^^ word, i think that it was used in desperation, should be going with a sohc, or a z32 maf, or can go bigger and use a q45 i think

18

im on the maf bandwagon, now when you say 3 seconds it dies, is that after the car was driven a bit and warm? or the car has been sitting for a day+ and it still only takes 3seconds?

a hot start and a cold start yeild different amounts of time in closed loop as i am sure you know.

19

the car is not driveable. unless you think i can take it for a cruise around the block in 3 seconds.

20

throttle position sensor?