VTEC Activation - K20A2 EK Swap

[jmr302]

I am sorting out a K20A2 swap in an EK hatch that someone else built. Currently I have 3 main issues:

1) VTEC activation
VTEC works initially but stops working a couple of blocks from home. Log files show that the ECU stops commanding it. If we key off-on, VTEC is functional again for the same brief period of time.

2) Low idle speed
Warm idle speed is normal initially (750 rpm), then drops to 500-600 rpm a few blocks from home. Key off-on resets this, just like the VTEC issue. S.TRIM is high in both conditions. AF ratio cycles very lean when the low idle speed occurs.

3) VSS signal
The speedometer is fully functional at all times but the ECU shows 0 mph. Occasionally it will register 3-5 mph. Cycling the key does not affect this.

The engine is a bone stock K20A2 with a header and CAI. Trans is a base model RSX 5-speed. Could this account for the VSS issue? It runs decently on this ECU calibration except for the problems listed. Any help would be appreciated. Thank you!

[CalibratEd]

I have not looked over the logs as I am away from my computer. I would say you may be experiencing an electrical issue. To start I suggest you set the VSS to constant speed to rule out a bad VSS. If the VSS is not working well Vtec will not engage.

I also suggest you make sure to calibrate the TPS.

I’ll have better insight once I look over the calibration file and logs.

-Ed

[Spunkster]

You have a number of error codes you must resolve in order for VTEC to work correctly.

[jmr302]

Thanks, @Spunkster. I'll check the codes and see what I'm missing here.

[jmr302]

So when VTEC is working it has P1298 ELD Circuit Voltage High.

When VTEC is inop a short time later, the codes are P0500 VSS Malfunction, P1298 ELD Circuit High Voltage, and P0325 Knock Sensor Circuit Malfunction.

Since P1298 is present when VTEC is working, I assume that's not causing the problem (although I'd like to fix it).

The P0500 makes sense because the VSS signal in the datalog is always 0 and it must take some running before the ECU figures out it shouldn't be zero. As mentioned originally, the speedometer always works properly, so I'm not sure I understand why this is happening. I have experimented with deactivating the VSS trigger for VTEC and this did not help, so I assume the main problem here is the P0325 Knock Sensor Circuit Malfunction. I will focus my troubleshooting there to start.