Attempting to adjust the timing via the distributor (if even equipped with one in this manner) will likely result in a misfire, poor performance, and potential damage to the engine. The only way to adjust the "timing" is indirectly by addressing potential issues that affect the PCM's calculations.
Here's what you should do instead of trying to manually adjust the timing:
1. Diagnose the Problem: If you're having timing-related issues (poor performance, rough idle, pinging/knocking), don't start messing with the distributor. Instead, use an OBD-II scanner to get diagnostic trouble codes (DTCs). Common culprits that *can mimic* timing issues include:
* Crankshaft Position Sensor (CKP) problems: A faulty CKP sensor will severely affect timing.
* Cam Position Sensor (CMP) problems: Similar to the CKP, a faulty CMP sensor will cause timing-related issues.
* Mass Airflow Sensor (MAF) problems: Incorrect air/fuel mixture will significantly affect engine performance, and could seem like a timing problem.
* Throttle Position Sensor (TPS) problems: Incorrect throttle readings will cause similar performance issues.
* Ignition Coil or Spark Plug Issues: Weak coils or fouled plugs will lead to misfires that can feel like a timing problem.
2. Check for Vacuum Leaks: Vacuum leaks can severely affect engine performance and can be mistaken for timing issues. Inspect all vacuum lines for cracks or loose connections.
3. Replace Sensors: Based on the DTCs or your inspection, replace the faulty sensor(s).
4. Professional Help: If you're not comfortable with diagnostics or repairs, take your vehicle to a qualified mechanic. They have the tools and expertise to properly diagnose and repair the issue. Improperly adjusting anything related to the ignition system in a modern engine can cause extensive damage.
In short: You don't set the timing on a 1997 Chevy 5.7L Vortec; the PCM does. Focus on diagnosing and fixing the underlying issue causing the symptom you're experiencing.
