Instead of setting timing with a timing light, you need to address potential timing *issues* through diagnostic procedures:
1. Check for trouble codes: The 1988 Suburban should have a system for retrieving diagnostic trouble codes (DTCs). These codes will point to potential problems within the engine control system, including issues that could *indirectly* affect timing. You'll need a scanner or a paperclip method (depending on the specific year and trim level) to retrieve these codes.
2. Inspect the components: Examine the following:
* Ignition System: Check the ignition coil, wires, and spark plugs. Worn components can affect ignition timing indirectly.
* Sensors: The ECM relies on various sensors (e.g., crankshaft position sensor, MAP sensor, throttle position sensor, etc.) for accurate timing control. Faulty sensors will lead to poor engine performance and potentially erratic timing. These sensors should be tested using a multimeter or a dedicated scanner.
* Vacuum Lines: Ensure all vacuum lines are properly connected and free from leaks. Vacuum leaks can significantly affect engine performance and potentially confuse the ECM's timing calculations.
* Wiring: Check for any damaged, loose, or corroded wiring in the ignition system and engine control system.
3. Data Logging (Advanced): A more advanced approach would involve using a scan tool capable of data logging. This allows you to monitor various engine parameters, including crankshaft position, intake air pressure, and fuel delivery, to see if the ECM is receiving accurate data and making appropriate adjustments to the timing. Discrepancies in the data could indicate a faulty sensor or other problem.
Important Considerations:
* No Adjustable Timing: Unlike older carbureted engines, there's no mechanical distributor to adjust the timing on a TBI system. Attempting to adjust the timing mechanically will likely damage the engine control system.
* ECM Control: The Engine Control Module (ECM) is the brain of the operation. If you suspect a timing issue, the problem most likely lies within the ECM, its sensors, or the wiring to them.
* Professional Diagnosis: If you're not comfortable with automotive diagnostics, it's best to take your Suburban to a qualified mechanic specializing in older GM vehicles. Incorrect diagnosis and repair attempts can lead to significant damage.
In summary: You don't "time" a TBI engine in the traditional sense. You diagnose and repair any problems affecting the engine's ability to properly manage timing *through the ECM*. Focus on the sensors, wiring, and trouble codes to address any potential timing-related issues.
