s5 turbo swap limp mode
08-04-16, 06:35 PM
#1
s5 turbo swap limp mode
Car is a 1990 gtu with jdm s5 turbo swap using the n374 ecu with rtek 1.7 w/ MOP delete. It definitely runs on both rotors unlike many of the other turbo swaps with the jdm ecu that i've come across that only have the front rotor getting fuel. All the wiring is the the s5 NA harness with the knock sensor and boost control solenoid wired in. I've already changed and set the tps with an fd one, cleaned the contacts and potentiometer in the afm, boost pressure sensor read 4.9v at 100mm/Hg when tested with vacuum pump, and i have a reman crank angle sensor on the way. From all the searching i've done in the past week the only things that should throw it into limp mode are the afm, map, tps, and mop. I'm at a complete loss at this point even disconnected the battery after each attempted fix to reset the ecu. Can't read codes with the check engine light since the n374 doesn't have a cel and trying to use LEDs in the diagnostic connector looks like it just pulses with the primary injectors. Also just a thought but could rtek have possibly sent me the wrong chip without the mop delete (even though it came with the sticker for the ecu). Any help is appreciated.
08-04-16, 07:03 PM
#2
What do you mean pulses w/the primary injectors. The test would be done w/key to on, engine not running. Does the car prevent you from climbing above a certain RPM but drives properly below that? A JDM ECU has a pin for fuel cut and if you have the wrong wire running to it supplying voltage the ECU will cut fuel.
Last edited by satch; 08-04-16 at 07:06 PM.
08-04-16, 07:16 PM
#3
with the key to on and engine not running my injectors start firing and the leds in the diagnostic connector appear to pulse evenly with the injector clicks (i know it sounds weird to me too). the car drives fine with part throttle though out the rpm range but is jerky under wot. when in neutral it will only rev til just over 4k at wot but again rev freely to redline at partial throttle. i should also mention i've gone over all my ground points.
which wire is this one that's linked to the fuel cut? i haven't seen any mention of it before
which wire is this one that's linked to the fuel cut? i haven't seen any mention of it before
08-04-16, 07:20 PM
#4
Your injectors should definitely not be firing w/key to on and engine off and your problem sounds like fuel cut thus you have to find which pin on the ECU is for fuel cut and make sure that wire has a ground on it.
EDIT: Actually, on an S5 JDM 374 ECU the fuel cut pin is 1M. W/key to on and engine running if it reads 12 volts then that is your problem.
Kompressor Logic (board member) had the very same problem as you and fixed it by addressing pin 1M.
EDIT: Actually, on an S5 JDM 374 ECU the fuel cut pin is 1M. W/key to on and engine running if it reads 12 volts then that is your problem.
Kompressor Logic (board member) had the very same problem as you and fixed it by addressing pin 1M.
Last edited by satch; 08-04-16 at 07:37 PM.
08-04-16, 07:42 PM
#5
pin 1m for my harness is a mileage sensor according to the fsm but i don't see anything with fuel cut. could the jdm ecu still use that as fuel cut and it was only changed with us series 5 models? if so would i run a ground from the ecu in its place?
the injectors firing with the key to on i would imagine is an ignition switch issue correct?
the injectors firing with the key to on i would imagine is an ignition switch issue correct?
08-04-16, 07:47 PM
#6
pin 1m for my harness is a mileage sensor according to the fsm but i don't see anything with fuel cut. could the jdm ecu still use that as fuel cut and it was only changed with us series 5 models? if so would i run a ground from the ecu in its place?
the injectors firing with the key to on i would imagine is an ignition switch issue correct?
the injectors firing with the key to on i would imagine is an ignition switch issue correct?
https://www.rx7club.com/2nd-generati...-swap-1100373/
Last edited by satch; 08-04-16 at 07:55 PM.
08-04-16, 08:29 PM
#7
alright so i'll remove that pin tomorrow to see if anything changes since its late now but i'll keep looking into the other differences mentioned in that thread as well as go over the japanese wiring manual in the mean time (should be interesting since my japanese is probably rustier than some of my cars parts).
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08-04-16, 11:13 PM
#8
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you can check it for codes too, it just doesn't use the CEL, you need an LED on the diagnostic connector
08-07-16, 01:13 PM
#11
ended up having a busy weekend with work but got out early today so i'll be tackling it shortly (after i eat some lunch). i did find some of the other threads where you were sorting out said issues and managed to get an idea of some of the other differences. one of those is the 1U wire which is for the A/T switch on na and mileage sensor 2 on turbos.
08-07-16, 05:31 PM
#12
Alright so i pulled pin 1M and didn't have a wire going to 1U. The good news is it doesn't have a jerky hesitation so much anymore but still loses power at wot. Gonna pull the ecu and check for any issues inside even though everything looked good when i installed my rtek chip a few months back. Almost feels like its not igniting the plugs properly/getting blown out under boost. New crank angle sensor should be in this week and i'll pick up new plugs when it does since mine are most likely fouled to all hell. I also wanna try to pull codes again but have to figure out why the primary injectors are firing before i try starting the car.
08-07-16, 07:43 PM
#15
You're saying that all of the ECU injector wires have 12 volts while idling but the wires which trigger the primary injectors have voltage drops w/key to on and engine off.
The primary ECU wires should be dropping w/the engine running as the voltage should be close to 6-9 volts or so.
The primary ECU wires should be dropping w/the engine running as the voltage should be close to 6-9 volts or so.
Last edited by satch; 08-07-16 at 08:01 PM.
08-07-16, 09:09 PM
#16
this is what the mazda wiring manual says so i guess its idling right as per mazda. i did notice a slight fluctuation on the primaries at idle so it must be a pretty fast ground. i'd imagine if i gave it some throttle there would be a more noticeable drop. with the engine not running and the key to on it is dropping to that 6-9 volt range though.
08-07-16, 09:54 PM
#19
Perhaps, but it could be something else at work (what? I don't know) but how about unplugging the CAS.
Also, check the wire which powers the ECU w/key to on as it should read 12 volts. The wire is usually Black/White and comes from the 4 wire plug of the main relay. The wire can also be found at a Green check connector near the lead coil which has few wires (B/W and 2 Yellow wires).
Also, check the wire which powers the ECU w/key to on as it should read 12 volts. The wire is usually Black/White and comes from the 4 wire plug of the main relay. The wire can also be found at a Green check connector near the lead coil which has few wires (B/W and 2 Yellow wires).
Last edited by satch; 08-07-16 at 10:05 PM.
08-08-16, 12:47 PM
#22
It appears unless some of the wiring is wrong then it appears the ECU could be your issue.
If you had an LED light you could use it to verify the ECU was pulsing a ground to the injectors. And the only reason for saying such is are you certain the injectors are firing and the clicking is not just a solenoid mimicking the sound? I just thought i would throw that out there.
If you had an LED light you could use it to verify the ECU was pulsing a ground to the injectors. And the only reason for saying such is are you certain the injectors are firing and the clicking is not just a solenoid mimicking the sound? I just thought i would throw that out there.
08-08-16, 03:44 PM
#24
well this is quite embarrassing but my eprom chip apparently rattled loose from the socket and i just found it sitting there in the ecu when i opened it up. this is probably one of the weirdest issues i've seen yet since the car still runs and drives. definitely going to makes sure it is secured much better before reassembly.
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