Experiencing idle issues after an H22 Obd2 To Obd1 Conversion can be frustrating. Many enthusiasts perform this conversion, often when swapping engines or upgrading ECUs in Honda vehicles like the Prelude. Let’s delve into a common problem encountered after this conversion: a fluctuating and stalling idle, particularly when the clutch is engaged.
One user reported this exact scenario after installing a chipped OBD1 ECU in their 2001 Honda Prelude with a JDM H22A engine swap. The car starts, but the idle dramatically drops to around 200 RPM and often stalls when the clutch pedal is pressed. This is accompanied by the oil light flickering due to the low RPM. Restarting the car becomes difficult immediately after.
This situation raises questions about potential conflicts arising from the OBD2 to OBD1 conversion process, specifically concerning the wiring harness and ECU compatibility. It’s suspected that the original OBD2 H22A4 wiring harness and P5M ECU might still be partially in play, causing issues with the newly installed OBD1 setup.
A possible solution suggested by ECU tuners involves disconnecting certain components that are typically controlled differently or are unnecessary in an OBD1 system. These components often include:
- EGR (Exhaust Gas Recirculation): This system recirculates exhaust gases back into the intake manifold to reduce emissions. OBD1 ECUs often manage EGR differently or eliminate it altogether in performance applications.
- EVAP Purge Solenoid (Evaporative Emission Control System): This system controls fuel vapor emissions. Similar to EGR, OBD1 management of EVAP can differ.
- Charcoal Canisters: Part of the EVAP system, these store fuel vapors.
Disconnecting these components at the engine wire harness might resolve the idle issue by removing potential conflicts between the OBD1 ECU and the remnants of the OBD2 system’s control over these emissions-related components.
An engine bay showcasing components potentially related to an OBD2 to OBD1 conversion on an H22 engine.
For anyone facing similar idle problems after an H22 OBD2 to OBD1 conversion, especially with a JDM H22A engine, investigating these disconnections is a worthwhile troubleshooting step. Consulting with tuning specialists familiar with Honda OBD conversions is also highly recommended to ensure proper setup and optimal engine performance. A professional tune can further refine the engine management and address any remaining issues after the conversion.
