There’s a common misconception about “overboost” being programmed into the Saab 850 Turbo’s ECM. In reality, the 850 and Phase 1 70 models don’t have built-in overboost parameters like similar Saabs. This makes them easier to tune, but also means that performance issues are likely due to other factors. If you’re experiencing a sudden power loss, it’s probably not overboost, but rather an electronic cut caused by issues like:
- Lambda Fuel Ratio: An incorrect fuel mixture can trigger the ECU to cut power.
- Excessive Knock: The engine’s knock sensor detects detonation and cuts ignition to prevent damage.
- MAF Over Parameter Issues: A faulty Mass Air Flow sensor can disrupt airflow calculations, leading to performance problems.
Saabs with overboost protection have safeguards in their engine management maps. The 850’s lack of these parameters simplifies tuning but requires careful attention to other components. If you’re experiencing ignition cut without a manual boost controller (MBC), investigate these potential culprits:
- Vacuum Leaks: Check all vacuum lines for leaks, especially the one connecting the intake manifold to the recirculation valve. A leak can disrupt boost pressure control.
- Faulty Actuator: A malfunctioning wastegate actuator or a seized rod can prevent proper boost regulation.
- Worn Boost Control Solenoid (BCS): The BCS controls boost pressure; a worn unit can cause erratic behavior.
Inspect your BCS. Stock BCS units usually have colored dots on the nipples: red to the turbo compressor, yellow to the wastegate, and white to the air inlet. If the colors don’t match or your BCS lacks markings, you likely have an aftermarket system. This is a good starting point for troubleshooting.
While your pipework connections might appear correct, double-check the hose from the intake manifold to the recirculation valve. It’s a common source of issues.
If you experience slight juddering under acceleration, it’s likely not ignition cut but rather ignition adjustment due to an over-rich fuel mixture. Start by inspecting the elbow at the intake manifold. A true ignition cut is a much more forceful event. You’ll definitely feel it. Ignition adjustment, on the other hand, is a more subtle sensation.
In summary, addressing performance issues in a Saab 850 Turbo in Glenboig requires a systematic approach. By understanding the absence of overboost parameters and focusing on potential causes like vacuum leaks, faulty actuators, and fuel mixture problems, you can effectively diagnose and resolve the issue, ensuring optimal performance for your Saab.
