Fuel System Issues:
* Fuel Pump: A failing fuel pump might not deliver enough pressure, causing sputtering and hesitation. You can check fuel pressure with a gauge (requires a special adapter). A weak pump might also cause the engine to sputter under load.
* Fuel Filter: A clogged fuel filter restricts fuel flow. This is a cheap and easy part to replace – do this first!
* Fuel Injectors: Clogged or faulty fuel injectors can deliver inconsistent fuel spray. Cleaning them or replacing them might be necessary. A fuel injector cleaner additive in the gas tank is a less expensive first step, but won't solve a completely clogged injector.
* Fuel Pressure Regulator: A faulty regulator could cause incorrect fuel pressure.
* Dirty Fuel Tank: Sediment and rust in the fuel tank can also impede fuel flow.
Airflow Issues:
* Air Filter: A severely clogged air filter restricts airflow, leading to a lean fuel mixture (too much air, not enough fuel), which causes sputtering and backfiring. Replace this immediately if dirty.
* Mass Airflow Sensor (MAF) / Air Flow Meter (AFM): This sensor measures the amount of air entering the engine. A faulty sensor provides incorrect readings, leading to a poor air/fuel mixture. Cleaning the sensor (carefully!) may help, but replacement is often necessary. (Note: 1989 models might have an AFM instead of a MAF sensor).
* Throttle Body: A dirty throttle body can restrict airflow. Cleaning it with throttle body cleaner is crucial.
* Vacuum Leaks: Leaks in vacuum lines disrupt the proper functioning of the engine's components, including the fuel system and ignition timing. Inspect all vacuum lines visually for cracks or disconnections.
Ignition System Issues:
* Spark Plugs and Wires: Worn or fouled spark plugs and cracked or damaged spark plug wires can lead to misfires, sputtering, and backfiring. Replace these if they are old or show signs of wear.
* Distributor Cap and Rotor: These components distribute the spark to the spark plugs. Cracks or corrosion can cause misfires. Inspect for damage or corrosion.
* Ignition Coil: A failing ignition coil can't produce sufficient spark.
* Ignition Control Module (ICM): This electronic control unit controls the ignition system. A faulty ICM can cause intermittent or complete ignition failure.
Troubleshooting Steps:
1. Start with the easy stuff: Check and replace the air filter and fuel filter.
2. Listen carefully: Does the sputtering happen consistently, or only under certain conditions (acceleration, deceleration, idling)? This can offer clues.
3. Check for codes: Does your Blazer have a check engine light? Get the codes read using an OBD1 scanner (if applicable, older models might not have OBDII).
4. Visual Inspection: Carefully inspect all vacuum lines, fuel lines, and electrical connections for any damage.
5. Systemic Approach: Tackle one system at a time. Address fuel system issues first, then airflow, and finally ignition if necessary.
Important Note: Without hands-on inspection and diagnostic testing, it's impossible to pinpoint the exact cause. These are potential problems, and the solution requires careful investigation and testing. If you're not comfortable working on your vehicle, take it to a qualified mechanic. Backfiring can indicate a serious problem and potentially damage your engine if left unchecked.
