sr20det hard to start when cold

[STEVES14]

setup
95 240sx with sr20det swap
GT30R, JWT ECU 3 bar program 740cc nismo injectors, Z32 mafs, intercooler, exhuast clutch, and so on
(no cams, stock)

Parts replaced before i start asking for help
CAS, coolant temp sensor, ingnitior, coil packs, O2 sensor, PCV valve, spark plugs, recheck grounds, to the coil packs and ecu grounds
oooooh.... and ecu code 21


ok heres the problem, it's been heappeing the last 2 months for some reason when the car is cold its a bitch to start i have to keep it at WOT for like 5 sec just for to catch alittle and then i feather the gas stumbles a bit for like .5 sec and idles like a champion at 1500-1700 rpm warms up a bit and drops down to 900rpm and holds strong the car drives fine all the power is there, so after i drive the car for a bit park it for like 2 hours go back to it it fires right up like it was a new car strange but after i drive the car again and park it over night it starts all over again

so to sum it up
when the motor is cold hard to start
when the motor is warm or hot FIRES right up with no issue
no matter what temp it's outside 30F or 100F if the motor is cold it's a bitch
to start

please help

[STEVES14]

never mind figured it out it was the start signal for the ecu pinout 34 it's suppoesed to get 12 volts when you put the key in start mode so the computer knows it's being started

[SoguRacing]

good job!!!!

[Yellow4g63]

Originally Posted by STEVES14

never mind figured it out it was the start signal for the ecu pinout 34 it's suppoesed to get 12 volts when you put the key in start mode so the computer knows it's being started

Too bad I saw this late I was just going to tell you that too.

[Sideways_blksr20]

And how do u fix this?im having the same problem

[Yellow4g63]

Here is what I found when I did my RB swap into my S13 (RIP). There is a wire thats suppose to go to ecu for the cold start signal. I'm sure it's the same on the SR20 too. Without the cold start signal the takes a little longer to turn over vs just turning right over right away.

[Sideways_blksr20]

how do I find this wire

[Sideways_blksr20]

anyone it only gives me a hard time when it's cold

[Yellow4g63]

S13 or S14?

[Sideways_blksr20]

S13 with s14 black top

[Yellow4g63]

I remember the cold start wire been in the dash plug for the S13's. It's been so long I think it was a 4 wire plug? it has the tach signal in it too.

[Sideways_blksr20]

so it goes from tach to ecu

[Yellow4g63]

more like the dash plug to the ecu. SR20DET Swap Engine Harness Wiring Diagram Guide SR SR20 it's that 1st plug it says to cut the orange wire is the one that needs the voltage going to it so the ecu knows the car is trying to start. But since u have a S14 harness in your car I'm not 100% sure which wire your going to use. The KA dash plug will still be the same orange wire tho.

[Sideways_blksr20]

thanks bro

[s14zouki]

my sr is doing the same thing, and always has. it doesnt matter if it's cold out. just like steve said though. i have an s14 with a s13 sr...can anyone help?

[ZooMxxl]

3 years of dealing with the rough cold start and going through a couple batteries (les schwab warranty), my car finally starts up on the first go like it should. so glad i found this.

[Sideways_blksr20]

Originally Posted by Yellow4g63

more like the dash plug to the ecu. SR20DET Swap Engine Harness Wiring Diagram Guide SR SR20 it's that 1st plug it says to cut the orange wire is the one that needs the voltage going to it so the ecu knows the car is trying to start. But since u have a S14 harness in your car I'm not 100% sure which wire your going to use. The KA dash plug will still be the same orange wire tho.

its an s13 so what do i need to do to fix this?

[Sideways_blksr20]

so what i understood its that i need to find this oraange wire from the tach and then rewire it to a 12v?

[Sideways_blksr20]

???????????????

[Alpha Residence]

Originally Posted by Sideways_blksr20

so what i understood its that i need to find this oraange wire from the tach and then rewire it to a 12v?

From the tach? No it comes out of the main harness from the ECU



that white plug has a orange wire thats the "ignition start" wire. Directly above the stock ECU location there is a dash plug. That wire needs to be ran up and spliced into the orange wire up on the dash side. If you're still doing your swap, cut that white plug off of your KA harness then match up all the colors and just plug that harness in.

[Sideways_blksr20]

the car its already running i bought it with the swap
so what i need to do its look for the orange wire from my ecu ,after i find this wire on the ecu i have to cut it and run it to the one from the dash side rigth?

[Sideways_blksr20]

????????????????????????????????

[Alpha Residence]

Originally Posted by Sideways_blksr20

the car its already running i bought it with the swap
so what i need to do its look for the orange wire from my ecu ,after i find this wire on the ecu i have to cut it and run it to the one from the dash side rigth?

yup, that about does it

[speedy13]

hey guys! I just joined in since I have the exact same cold start problem. I have tested everything possible, but no luck. But this thread sounds sensible. ok, I have an sr20de, p10 primera. it started having the same problem mentioned at the very top straight after I had my starter motor rebuilt. it starts up perfect when the engine is warm/hot. But needs throttle to start when cold.
H E L P!

[Sideways_blksr20]

car its at the paint shop ill try to do the wire thing and i let u know

[speedy13]

Thanks bro! I just couldnt follow up as to what is to be done with that start signal wire.
That pinout 34 seems to be color purple in my sr20de.

[GSXRJJordan]

Originally Posted by speedy13

Thanks bro! I just couldnt follow up as to what is to be done with that start signal wire.
That pinout 34 seems to be color purple in my sr20de.

More likely that the pinout is different - look for a orange wire with a silver stripe that goes to the dash plug, like in the pic.

But since the SR20DE came in USDM cars, why not just check the FSM for a ignition start wire?

[obsolete]

does battery have anything to do with this?

[speedy13]

The battery is new. I replaced Fuel filter, distributor, fuel pressure, coil, fuel rail, MAF, Ignition Barrel, & spark plugs.

[tacoboy]

I'm having the exact same issue as the OP. However, all of the wiring is legit and the orange wire is getting 12.5 volts when starting. Any other ideas? Could it be coolant temp sensor? Only happens when cold, the throttle needs to be cracked a bit, and I get a bit of black smoke (unburnt fuel).

Cheers!