Strange issue with timing Fixed

With it being a completely computer controlled mod motor-I’d say that’s pretty normal. If it wasn’t, you would have a list of timing component engine codes to go along with it

Common Causes of Erratic Timing​

Dirty or sticking Idle Air Control (IAC) valve

The PCM uses spark advance to counter idle airflow fluctuations. If the IAC sticks, the PCM will chase the idle with spark.
Check: If idle RPM drifts or hunts along with the timing, pull and clean the IAC with throttle-body cleaner.


Vacuum leak (unmetered air)

A small leak near the intake manifold, PCV hose, or vacuum tee can cause erratic idle fuel trims and timing correction.
Check: Spray carb cleaner around suspect areas and listen for RPM changes, or use a smoke test if available.


Camshaft Position Sensor (CMP)

A weak or oily CMP can cause timing instability at low RPM if the signal is noisy. The 2V engine uses it for sequential injection and ignition phasing.
Check: Inspect connector and wiring; replace sensor if there’s oil intrusion or intermittent signal in a scan log.


Crankshaft Position Sensor (CKP)

Less common, but a marginal CKP can cause the PCM to re-sync timing constantly.
Check: Look for consistent RPM signal in live data — any dropouts mean it’s time to replace it.


Fuel trims and O₂ feedback

You just replaced the O₂s — verify both are switching normally (~0.1–0.9 V) and trims are close to ±5% at warm idle.
If one bank’s trim is off, the PCM will vary spark on that side to chase stoichiometry.