R33 GTR misfire/spitting one cold start up while under load

[dak24]

Hi everyone, I have a issue with my r33 gtr and I'm unsure of what's causing the problem. On a cold startup when driving the car for the first few minutes when it's warming up the motor acts like its misfiring/spitting while drive but not while sitting at idle. But after driving for a few minutes and the motor warms up it goes away and runs great. I have new split fire coils so I know it's not the coils. Any ideas on what the issue could be?


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[caliber676]

Cas, ignitor, mafs

[Skym]

Stock ECU has a warmup mode where it pulls ignition timing, etc to protect the engine (rev limiter on BMW). I think Link ECU, ViPEC ECU have this feature as well (might be installed inside stock ECU casing).

But sounds like it's a fuel cut rev limiter. But not sure which one as don't know the rpm it is happening at.

Most likely it might have something to do with intake airleaks just before the MAF's (makes ECU hit boost cut earlier than it should) or just after them which makes the engine stutter, which is similar to missfiring coilpacks.

[dak24]

It happens right around 1700-3200 rpm, and I barely have to be on the throttle when it's happening. The ecu is stock and still has the seals on it from Nissan so I know it hasn't been touched


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[Bruizer]

This exact thread is a recurring one but since your new here..
When were the plugs last changed? You're running the factory Japanese tune on non Japanese fuel and altitude, so on. have you talked with your tuner? When was the mafs last cleaned? Ate the coil packs stock? .

[dak24]

I changed the plugs a year ago along with the mafs. It can't be tuned with the stock ecu. And I replaced the coil packs last August with split fire coils.


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[Nismo_line]

I'm having the exact same issue. I have new plugs, new coil pack harness. Still need to adjust my tps and my timing little bit more but it's like the motor is getting to much fuel. I will try swapping out the ignitor for a different one.

[Skym]

Sounds like TPS or fuel cut / boost cut.

The ignitor can fail (solders on the inside get dry due to heat) and runs on 5 cylinders.

Failed CAS bearings can make the base ignition timing retard 1-2 degrees, but would get hard starting when hot, cold.

Failed TPS can cause missfiring (lean missfire) and would happen at lower rpm.

Failed fuel pump or wiring to fuel pump could cause missfiring (lean missfire).

Failed FPR (Fuel Pressure Regulator) can causes lack of fuel (lean missfire).

Would be best to fit a wideband, fuel pressure gauge and diagnose on a dyno where you can load up the engine.

[Nismo_line]

I will be fitting a wide band this week as well as setting my tps to the proper voltage at idle to make sure it's set right.

[Nismo_line]

installed a wideband and adjusted my tps properly. It got little better but when this happens the afr is at 13-13.5. when engine is warm and same situation it is at 14-14.5. Car runs rich I know and some times when sitting at a light while idling the afr will be sitting at 14-14.5 and then the rpm will drop about 150 then go back up and the afr will drop to 13 then go back.