* Incorrectly adjusted carburetor (if equipped): If your S10 has a carburetor, improper adjustment during the tune-up (or a pre-existing misadjustment) can lead to a rich mixture. This is a common cause of black or gray exhaust smoke.
* Faulty fuel injectors (if fuel-injected): Fuel injectors that are sticking open or delivering too much fuel can cause a rich mixture and gas smoke. This is more likely if the tune-up involved cleaning or replacing injectors. A faulty injector could also have been there before, masked by something else that the tune-up fixed.
* Vacuum leak: A vacuum leak can disrupt the air/fuel ratio. Air enters the engine without being measured by the sensors, causing the computer to compensate by adding more fuel, resulting in a rich mixture. A tune-up might have inadvertently created or worsened a pre-existing leak.
* Faulty oxygen sensor: The oxygen sensor tells the computer the air/fuel ratio. A faulty sensor will result in incorrect fuel delivery. It might be unrelated to the tune-up but a tune-up might have highlighted its deficiency.
* Clogged or dirty air filter: A restricted airflow due to a dirty air filter will lean out the fuel/air mixture, but the system might attempt to compensate by making a rich mix causing smoky exhaust.
* Improperly adjusted distributor (if equipped): If the distributor's timing was off after the tune-up, this could result in incomplete combustion and unburnt fuel in the exhaust.
* Problem with the PCV (positive crankcase ventilation) system: A faulty PCV valve or other issues within the PCV system can affect the air/fuel mixture, potentially leading to a rich condition.
What to do:
1. Check for obvious issues: Inspect for vacuum leaks visually around the intake manifold and vacuum lines. Check the air filter. Check your spark plug wires, a missed or swapped connection could be causing incomplete combustion.
2. Get a professional diagnosis: The most reliable approach is to take the vehicle to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately and perform the necessary repairs. They can test the fuel injectors, oxygen sensor, and other components to identify the root cause.
3. Consider the tune-up itself: If the problem started *after* the tune-up, it might help to have the mechanic review the tune-up procedure to check if something was overlooked or misadjusted.
Don't continue driving with excessive gas smoke. It's inefficient, and potentially damaging to your catalytic converter.
