R34 GTT Error 21 + misfire

[rahilp]

Hi there I've currently have Error 21 (ignition signal circuit). I've also have a misfire happening only at low RPM. It will stall out if you accelerate approx 50%, if you go 75% it will drop the revs and almost stall then shoot up, but accelerate slowly it will go just as normal (these are all from stand still and rolling slowly)

Firstly the car is R34 GT-T manual running stock 
ecu 
Injectors
Turbo
Throttle body with TCS still

Aftermarket
Greddy intake
Front Mount intercooler
Splitfire Coilpacks

I've installed the splitfire coilpacks last week (brand new) along with spark plugs gapped at 0.8. I checked the coilpack loom for constant ground + 12v with the ign on and tested trigger signal for continuity from the ecu to the coilpack loom (so those have all passed) I've heard people say replace the loom but idk if thats going to resolve it for me

Injectors were cleaned and flow tested about a month ago

I've heard CAS could be a problem, I assumed mine was fine and wasn't going to be and issue. But I bought another one and it was still the same issue. Then borrowed someone's with a working one and still same issue

Hope someone has some knowledge

[GTSBoy]

Check the health of the engine earth strap.

Did you look at the spark plugs?

[rahilp]

Spark plugs were replaced, but ill look at that as the battery was relocated to the boot and it was earthed near the boot

The car had a period where it was down for about 3 months and had a few things done

[rahilp]

On 9/17/2021 at 9:20 AM, GTSBoy said:

Check the health of the engine earth strap.

Did you look at the spark plugs?

Sadly earth strap didn't fix it

[joshuaho96]

The ignition signal circuit error means something in the path between the ECU ignition output to the coilpack trigger is broken open. Start with checking the connectors at the coilpacks and work backwards from there until you find it.

[rahilp]

On 9/18/2021 at 10:40 AM, joshuaho96 said:

The ignition signal circuit error means something in the path between the ECU ignition output to the coilpack trigger is broken open. Start with checking the connectors at the coilpacks and work backwards from there until you find it.

I guess I can put my multimeter on the ecu loom and see if there's any output voltage when the car running. But I had continuity on all the trigger wire from the coilpacks plug to the ecu

[joshuaho96]

On 9/17/2021 at 9:07 PM, rahilp said:

I guess I can put my multimeter on the ecu loom and see if there's any output voltage when the car running. But I had continuity on all the trigger wire from the coilpacks plug to the ecu

The ECU sees the entire circuit path. With a smart coil the path it's seeing is ECU output -> coilpack trigger -> coilpack ground common with ECU ground. I would recommend getting a spark plug lead extension so you can put a timing light on the car and seeing what things look like on each cylinder. That will at least tell you what you're dealing with.

Also, make sure you're reading the code correctly and not accidentally flipping a code 12 into a code 21.

[GTSBoy]

And continuity testing doesn't prove that the whole wire is good. You could have just one thread of copper still connected and a multimeter set to "continuity" will still beep. But that wire won't carry much current. So continuous and "functional" are not necessarily the same thing. Check resistance.

You can also measure the resistance of a single strand of copper from a similar wire and compare to a 3m length of wire to see what range of resistances could be possible, to guide your eye.

[rahilp]

On 9/18/2021 at 2:40 PM, joshuaho96 said:

The ECU sees the entire circuit path. With a smart coil the path it's seeing is ECU output -> coilpack trigger -> coilpack ground common with ECU ground. I would recommend getting a spark plug lead extension so you can put a timing light on the car and seeing what things look like on each cylinder. That will at least tell you what you're dealing with.

Also, make sure you're reading the code correctly and not accidentally flipping a code 12 into a code 21.

Might invest in one or see if there any reputable mechanic available this week.

And its 2 short flashes pause followed by 1 quick flash

[rahilp]

Thought I'd have a looking at the timing belt. And it is out by two teeth would that be enough to cause this?

[joshuaho96]

On 9/18/2021 at 5:06 PM, rahilp said:

Thought I'd have a looking at the timing belt. And it is out by two teeth would that be enough to cause this?

Don’t think it would cause your code 21 but that is not a good sign. I would fix that before it causes more problems.