Here's what you should do instead:
1. Check for Diagnostic Trouble Codes (DTCs): Use a scan tool (OBD1 scanner) to check for any trouble codes stored in the PCM (Powertrain Control Module). These codes will give you clues about any potential problems that might be affecting engine performance, which could be *mistaken* for timing issues. Addressing the underlying issue is essential before proceeding.
2. Verify Engine RPM: Ensure the engine is idling smoothly at the correct RPM. The idle speed should be specified in your owner's manual or a repair manual for your specific vehicle. A faulty idle air control (IAC) motor or other idle-related issues can affect engine performance and be misinterpreted as timing problems.
3. Check for Vacuum Leaks: A substantial vacuum leak can significantly impact engine performance and might be mistaken for a timing issue. Carefully inspect all vacuum hoses and connections for cracks, leaks, or loose fittings.
4. Inspect the Ignition System: Ensure that the ignition system components are in good working order. This includes the spark plug wires, distributor cap, rotor, and spark plugs. Worn or damaged components can lead to misfires, which might feel like a timing problem.
5. Check the Engine Sensors: Several sensors feed data to the computer to adjust ignition timing. Malfunctioning sensors, such as the crankshaft position sensor (CKP) or the MAP (Manifold Absolute Pressure) sensor, can cause poor running and incorrect timing.
In short: You don't adjust the timing on a 1993 Chevy Blazer 350 TBI engine manually. The computer controls it. Troubleshooting poor engine performance should focus on diagnostics and repairing any detected problems within the engine's control system, rather than attempting to manually alter the timing. A qualified mechanic with a scan tool and the proper knowledge is the best resource for diagnosing and repairing any performance issues. Improperly attempting to adjust the timing yourself could seriously damage your vehicle.
