Startup problems with K24 engine

Hi everyone,

I’m having an issue with a K24A8 swap using a Haltech Nexus R3 ECU.

The engine cranks and starts, but it sounds like it is only firing on 3 cylinders and runs very rough.

So far, I have checked the following:

• All 4 OEM injectors work correctly using the ECU’s injector test function.

• All 4 ignition coils have been tested and appear to work correctly.

• Ignition timing has been checked using an inductive timing light.

• Base ignition timing is currently set to 0° BTDC.

• The injectors are OEM K24A8 injectors.

• The engine has RPM signal while cranking.

• The issue appears to be present immediately after starting.

What would you recommend checking next to identify which cylinder is not firing?

Thanks!

Ways to determine a misfiring cylinder.

- Use an Infrared temp gun look at the exhaust as it exits the head. Missing cylinder will be colder than the others.

- While the engine is running, disconnect either the coil or injector for each cylinder (one at a time). If the engine runs worse, it's not that cylinder. If the engine doesn't change at all, then that cylinder has no combustion.

Once you know what cylinder, start by checking the spark plug (is it fouled - try cleaning), perhaps replace it. Measure compression / leakdown in that cylinder. Swap coils and injectors to see if the problem follows the coil/injector or stays with the cylinder.

Good Luck!

Update:

We checked which cylinders were contributing, and the misfire changes between cylinders during the same starting attempt. It is not consistently the same cylinder.

The injectors and coils have been individually tested and appear to work correctly.

Since the issue moves between cylinders, we are currently unsure if this could be related to synchronization, ECU configuration, or something mechanical.

Any ideas on what could cause this behavior?

I would look for any diagnostics available in the Haltech Nexus ECU. Particularly look for any trigger (Crank / CAM sensor) errors, as those can affect fuel injection and spark timing.

Also, have you tried adjusting the overall fueling in the idle areas to understand if you have a lean or rich misfire. Again, the plug condition may give you a direction to try.

Does it clear up, if you hold the throttle open a bit so the engine runs at 2000-2500 RPM. Often it's easier to get a new calibration running in that area first, then work your way down to idle.