Building small web tools to visualize turbo pressure and temperature data from JAC S5 engines.

Modern Haima engines include advanced electronic throttle control and multi‑point fuel injection systems optimized for low‑speed torque and emission efficiency. In daily repair operations, these systems often show calibration drift after 60,000 km due to sensor hysteresis and aged ignition maps.

During the last months at our workshop in Tehran we observed several Haima repair shop units with inconsistent idle speed caused by slight mismatch between IAC stepper control and ECU baseline airflow table.

1️⃣ Understanding the Real Cause

Many technicians replace actuators before examining the adaptive fuel trims. But on Haima engines, the real issue often lies in the temporal alignment between throttle opening rate and manifold pressure transient. Using only an OBD snapshot isn’t enough — data logging under dynamic load (i.e., simulated hill climb) gives more reliable insights.

2️⃣ Calibration Strategy

The most stable correction we found was clearing the long‑term fuel trim (LTFT) values, running the idle learning cycle, and re‑mapping the ignition advance using a scanner that supports GDI adaptive tables. This can recover up to 5–8 % of lost efficiency.

3️⃣ Preventive Engineering View

From a thermal standpoint, Haima’s radiator core is small relative to engine bay volume, which increases localized heat stress at the throttle body zone. Regular coolant replacement with G12++ improves the actuator’s life‑cycle notably.

⚙️ Engineering note:

ECU synchronization and thermal equilibrium are inseparable in modern Haima vehicles; diagnostics should always consider both software behavior and heat‑transfer equilibrium rather than component isolation.

Written from field observations as part of engine system diagnostics training in Tehran.