Possible Causes:
* Vacuum Leaks: A significant vacuum leak will allow excess air into the engine, making the mixture lean. Check all vacuum lines for cracks, loose connections, or missing lines. Pay close attention to the lines connected to the intake manifold, brake booster, and other vacuum-operated components.
* Fuel Delivery Problems:
* Fuel Pump: A weak or failing fuel pump might not deliver enough fuel pressure. You'll need a fuel pressure gauge to test this. The pressure should be within the specifications listed in your owner's manual or a repair manual.
* Fuel Filter: A clogged fuel filter restricts fuel flow. This is a relatively inexpensive and easy component to replace.
* Fuel Injectors: Clogged or faulty fuel injectors can deliver insufficient fuel. This often requires professional diagnostic tools or replacement.
* Fuel Pressure Regulator: A malfunctioning regulator might not maintain the correct fuel pressure.
* Mass Airflow Sensor (MAF) Sensor: The MAF sensor measures the amount of air entering the engine. A faulty MAF sensor can provide inaccurate readings, leading to a lean condition. Cleaning the sensor (carefully, following instructions) can sometimes resolve this. A faulty sensor will need replacement.
* Throttle Position Sensor (TPS): The TPS tells the computer the throttle position. An incorrect signal can cause the computer to adjust the fuel mixture improperly.
* Oxygen Sensor (O2 Sensor): The O2 sensor monitors exhaust gases and provides feedback to the computer to adjust the air/fuel mixture. A faulty sensor can cause the computer to make incorrect adjustments, leading to a lean condition. These are common failure points.
* Computer/ECM Issues: In rare cases, the engine control module (ECM) itself might be faulty, causing improper fuel delivery. This is usually the last thing to suspect, as it's difficult and expensive to diagnose and repair.
* Air Intake System: Restrictions in the air intake system (dirty air filter, blocked intake) can cause a lean condition, although this usually manifests as reduced power rather than other lean symptoms.
Symptoms of a Lean Condition:
* Poor Fuel Economy: One of the most common symptoms.
* Rough Idle or Stalling: Especially noticeable at idle or low speeds.
* Hesitation or Misfires: The engine may hesitate or misfire under acceleration.
* Check Engine Light: Almost certainly illuminated, with diagnostic codes stored in the ECM. Have the codes read at an auto parts store (many will do it for free) or use an OBD-II scanner.
* Backfiring: In severe cases.
* Overheating: A lean condition can cause excessive engine heat.
Troubleshooting Steps:
1. Check the Check Engine Light: Get the diagnostic trouble codes (DTCs) read. This is the most important first step.
2. Inspect Vacuum Lines: Look for any cracks, leaks, or loose connections.
3. Replace the Fuel Filter: This is a cheap and easy fix that often resolves fuel delivery issues.
4. Check the Air Filter: Ensure it's clean and not restricting airflow.
5. Test Fuel Pressure: If you have the tools and knowledge, test the fuel pressure.
6. Clean the MAF Sensor: Be gentle! Use MAF sensor cleaner.
7. Consider professional help: If you're not comfortable performing these checks, take your Blazer to a qualified mechanic. They'll have the tools and expertise to diagnose the problem accurately.
A lean condition can cause serious engine damage if left unaddressed. Don't delay in getting it checked. Remember safety first when working under the hood of a vehicle.
