Ignition breaking up at vtec, and sometimes cuts off.

[tharshan]

Hello.

So I have a very weired problem.

I have had the car for 15 years, and have many builds around it. Now I have ran in to very weired problem. Ignition break up on vtec crossover

The vtec crossover is setup at 4000 rpm. So if I start my pull from below that point, in the higher gears, the car pulls without any issues all the way to the redline.
If I start the pull in 1. gear, and sometimes higher gears, the car will break up ignition at the vtec crossover and then start to go, and if so it will pull all the way to the redline without any issues.
If I start the pull in any gear, above 4500 rpm, the ignition will completely cut off. The car will feel like I have shut down the throttle. This will happen 9/10 times.

Spec list is pretty long, but what you need to know I think: 97' EK4, b18c sleeved, custom cams, custom turbo kit, Pulsar G40, id1700x, Hondata S300v3, Hondata cpr, Denso coils, rywire cpr harness

What I have done lately:
I had a big voltage drop issue, it will be running 12-13V only. Last winter I upgraded the main cables from alternator-fusebox-starter-battery. Now the voltage is 14-0-14.3.

What I have tried:
- Changing the vteccross over moves the problem
- Tried different calibrartion(more fuel, less fuel. I do tune the car on the street)
- New ecu with new s300v3
- new obd1-obd2a adapter
- Checked and cleaned the injectors
- fuelpressure is stable according to the logs
- Ran a wire from obd adapter straight to vtec solenoid(To rule out the harness)
- New vtec solenoid
- 2 different spark plugs(ngk iridium and normal ngk, all resistor plugs)
- Checked the wiring for the CPR( I have had the cpr kit for years)

The car otherwise runs without any other issues.

I'm a bit lost at this point.

Video which belongs to the log. You can that when I start the pull it breaks up on the vtec crossover. When I go on throttle at around 5000rpm it just shuts down and then starts to pull 2 seconds later
https://youtu.be/teKpCIdTyII?si=JM1VA7VTk0Sd7O0o

[Spunkster]

Check the grounds in the engine bay as it sounds like it is grounding through the vtec solenoid and causing a rev limit.

[tharshan]

Yes, that's my thought also, so I have done following:

These are my grounds:
50mm2 ground from battery to chassis
50mm2 ground from transmission to chassis
16mm2 ground from valvecover to chassis
16mm2 ground from back of the head to chassis

additionally I have added 2 more 2mm2 ground from ecu power ground to thermostate.

I have also checked thermostate ground which clean. All chassis ground is grinded down to metal.

[Griinchy732]

Hey bro were you able to figure out this issue ? I’m going through something very similar . Break up / stutter after vtec on half throttle . If I full throttle it’s ok , but half throttle at Vtec cross over just hesitates