Nistune Forums

Specs:
S2 Rb25 in S1 R33
Yellow jacket coils NGK BPRE7ES @ 0.8 brand new
S1 Ignitor
S2 Can angle sensor
Siemens 760 top feed injectors with rb26 rail
3076R
Z32 AFM

Making 450rwhp tuned.

So my second S1 engine was giving me tonnes of blowby so I swapped it out for an auto S2 motor. Installed as per usual. No wiring changes just unbolt and install. AFM is blow through. Exact same setup that was working. I drove the car with the shit engine to the garage.


Hydro locked it due to injector wiring shorting out. Fixed that problem. Engine fired up but was misfiring.

Took the coils out checked the resistance on them. All equal at about 1ohm as per the FSM.
Check the ignitor chip (TPU) and it was good as per the FSM.
Continuity on the coil harness was good. No resistance on any of the earth/12v/signal wires.

Plugs spark when grounded and I manually spin CAS I can visualize spark.
RB26 resistor box and injector wiring is good. All injectors clicking as per normal.
Fuel pressure 40psi with vacuum

Here's the thing. We put it all together and it ran great after that. Took it for a few test drives around the neighbourhood. Started it, stopped it, hit a bunch of bumps and everything. All good. Decided to drive it home (20min drive). Parked it over night.

Came out this morning and it was fucked. Misfiring again. Pulled the coil pack harness at each coil pack but all seemed to change the same with the engine. Wiggled all the wiring around to no avail.

Nistune seems to report very jagged timing changes when its misfiring. I am not at home but will attach the bin and log when I can tonight.

Was previously able to hear dead cylinders when I was troubleshooting by pulling the ignitor wiring and could audibly hear a change. Now not so much.

How much rewiring has there been going on here?

Main reason for my question is that the MAF input signal looks very jumpy, just like your timing output! Not that this will necessarily cause the misfires but it could be contributing

Misfires can happen due to things like cracked sparkplug or lead as I've experienced and very difficult to find

Anyway back to the MAF input, is it shielded from the ECU right through to the engine? With a nice smooth airflow it should not be so jumpy (unless the misfires are causing this fluctuation in voltage?)

AFM wire is shielded through the engine bay.

seems that if i get the car nice and warm it drives great.,,We checked the temp sensor and it checked out.

When it is driving good my vacuum is better, AFM voltage and battery voltage are stable as well.
Was out driving today once good and warmed and made 1.35bar no issues.

I know its been really cold here around -10 with wind at night, maube the 7 heat range on the plugs is too cold?

Alternator is not charging well.. possible earthing issue as voltages jumps around alot.
temperature affects ground points.

is the oxygen sensor dead?
speed sensor dead?
lines 140 to 150 indicate a TPS issue.

TPS, or oxygen sensor causing lean conditions.

not much else to diagnose without exhaust gas mixtures in the log.

Always had that same issue with the alternator. I have 2 engine grounds to the chassis. Should I add more? (It was around -10degC when this was happening)

O2 sensor was unplugged, its tuned to not use the O2 sensor unless its between 2800-3400 in the first 3-4load columns.
Speed sensor works and shows in Nistune in real time, not when recorded and played back...strange.
TPS issue? I know its saying 0.46/0.72...it had been corrected if you see in the next log its working. Im using one of those cheapo Taiwanese 100mm throttle body and the shaft is less then perfect and has issues. It however was not the problem as once properly adjusted and set the issue continued.

My LC1 sensor is dead, been meaning to replace it to see. I know its not helpful when its not there...

Its been warmer outside now (around 0degC overnight and +5-10degC during the day and the car run better now. Still sputters a bit when cold but drivable now when cold...leaning more to the TPS being problematic during a certain portion of the range but does read 0.5ish closed and 3.5v wide opened.

All in all the car is much better with no interventions, just kinda fixed itself as it warmed up. Maybe it was temperature related? The AFM was not changed, voltage checked out as per the FSM with 1.1-1.2 on idle. The AFM is setup as blow through.

ok, if engine gounds are good and clean, adding more than what is require can make problems so best not.

maybe TPS is erratic causing the issue.

take up the speed sensor issue with Matt. it must appear in logs if its one of the registers being monitored.

any analogue electronic devices like TPS or CTS will be affected by temperature. if its excessive then replace it.
It does appear that the TPS is bouncing though and doesn't correlate to the Mass air flow reading.

try another battery as they are affected by temperature dramatically.
get the alternator load tested as the voltage reported is not sufficient for the ECU to fire injectors consistently due to the fact they aren't standard and you haven't changed the voltage latency change correctly for them.

The TPS is adjusted and just has a small dead spot where it skips from 0.58-0.62 as 0.60 doesnt seem to register. The rest of the range is perfect.

Speed sensor works fine in the gauges within Nistune but doesnt record. Didnt happen last summer when I checked last.

Battery was changed. The only thing I can think of is the alternator and I know the voltage is low but its always been that way with 3 different alternators and 3 different motors.

Speed input to Nistune is showing 0 which means ECU isn't seeing the speed. Check wiring from speedo cluster to ECU if you are seeing speed on your dash

So in the log you have is the misfire at 11:57 - 12.62 where we see the RPM bouncing around 2000rpm before it goes up (and then another misfire at 3850rpm @ 15.21)

There are no massive fluctuations in timing at these points. MAF voltage nice and smooth, TPS holding about 2 volts

As far as the ECU side of things go it looks fine from that log. I cant see any thing to cause a misfire which puts it back to some potential mechanical issue