cumberlandrx7

Ok let me begin by saying I tried for numerous hours to search for an answer before posting this thread but nothing has worked.

I recently swapped a JSpec T2 engine in and it came with a N3A7 ecu which was the wrong one but the engine started and idled just fine but couldn't rev and was giving strange errors so I bought a N374 ecu recently and I plugged that in but now the car wont start, it just cranks over and over and i want to prevent flooding but at this rate it will just flood. There is fuel to the engine, there is a spark from every coil, the spark plugs are 'fairly' new but i'm not sure if those could be it. One thing I do notice is the starter motor grinds sometimes when I turn the key off, is this the signs of a faulty starter motor? I was told the engine had great compression when I got it and I mean it started and idled perfectly before so the engine works but it's just having issues starting up. Any ideas???

RotaryRocket88

iTrader: (7)

Is this a stock N374 or a chipped version? In general, the N374 Jspec ECU and US-spec wiring do not mix well.

cumberlandrx7

It is the stock N374, and I posted a thread before asking which to buy the N374 or N370 and was told the N374.

RotaryRocket88

iTrader: (7)

This thread? https://www.rx7club.com/2nd-generation-specific-1986-1992-17/tii-ecu-problems-866512/

It looks like you were told wrong. The stock N374 has a habit of not firing the injectors properly when used in combination with US-spec wiring. This might lead to the condition you're experiencing. All of your wiring is US-spec, so the ECU should match (N370). The fact that the core and some sensors are Jspec doesn't matter.

89fc3sgtu

iTrader: (3)

i had the same problem the n374 wont fire the rear rotor injectors, i would suggest getting an n370 ecu, but if you want to get it stated on only the front rotor try pull starting, rotaries need alot of rpm to start

cumberlandrx7

Does anyone know why the N374 has a habit of not firing the rear injectors?? I dont see the wiring being so different that a car wont run with an ecu, there must be a way to fix that issue. Possibly trace down the grounds from the ecu to make sure it is grounding out the injectors properly??? I'm sure tons of people use the N374 ecu with the US spec harness but anyone know if anyone has posted on getting it working???? It's almost winter here and I really dont feel like waiting 3 weeks for another ecu to ship.

RotaryRocket88

iTrader: (7)

Some people use chipped N374 ECUs, but just about everyone that tries to use the stock version runs into the injector problem. I don't know of any information on fixing the problem because I don't think anyone has. Buy a chipped version of the N374 (knightsports, etc...) or an N370.

89fc3sgtu

iTrader: (3)

i know the jdm cars have some what different wireing harness than the a-spec ones, but they are minor differences. i cant explain why but i trie 3 differnt n374 ecu's and not one of them fired my rer injectors, then i got an n370 and it ran perftect

cumberlandrx7

Ok just posting some info for future problems like this. I hooked up an LED to the positive side of the battery and the other side to 1 of 4 pins on the ecu. The 4 pins were 3Y, 3Z, 3W, and 3X. These 4 pins are connected to ground and when cranking ground out the injectors to fire them. Here is what I learnt with the N374 ecu plugged in. The light was on with the key out of the ignition and when the key was turned to the on position the light turned off, this is the case for all 4 pins and this is how it should work so all is fine. When the engine is cranked the LED should flash (ie the injectors firing), well it wasn't only the rear injectors that weren't firing but the front secondary injector did not go either, only pin 3W worked which is the front primary injector. So this is obviously either a faulty ecu or a mix match with wiring on the US harness and the N374 Jspec ecu isn't working. Hopefully this helps people who run into this problem or are looking into possible problems with this ecu and harness match-up. My next step is a long wait for a N370 ecu (if I can even find one).

cumberlandrx7

If I was looking at chipped N374 ecu's what should I be aware of?? are the ones in the links below reputable ones? does anyone suggest I use chipped over the stock N370?? here are just a couple i found on Ebay.

Ecu #1

Ecu #2

Ecu #3

also with these ecu's do I have to worry about them not working aswell or since they're chipped and the ignition mapping changed should they work?? should I look for one chipped for US harness?? I just don't want to get the wrong ecu again.

RotaryRocket88

iTrader: (7)

Here are some threads on the topic.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/re-animeya-redom-ecu-481235/
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/tuned-ecus-591546/
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/redom-ecu-593084/

Those ebay prices are pretty damn high too. I'm not sure what an N370 sells for given its rarity, but I would think it'd be lower than that.

Gregory Casimir

iTrader: (8)

so did they ever find out what that black box was?