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i'm fairly new to tuning and i can not figure this out.
i have been trying to get a stable idle for over a month now, but after reading ALOT of forums and doing the hpa courses i'm still having the same problem.
i'm truly at a loss and i would really appreciate if someone could help me out.
i have a 99 mazda mx5/miata with the 1.6 nb engine.
Things that lower the engine torque (and thus idle speed):
- Reduced airflow (ie, close the throttle more)
- Retarted Ignition (reducing timing in the area around and above the target idle, will slow the engine into the idle range.
With this information in mind:
- Have you checked for vacuum leaks (includes stuck / backwards PCV valve, stuck EGR mechanism, leaking manifolds, cracked vacuum hoses)?
- Have you verified the ignition timing with a timing light.
- Some other mechanical problem like: cam skipped timing and is running advanced, or sticky throttle linkage that doesn't return to the stop, worn throttle shaft.
Sticking brake booster/servo check valve can also cause issues.