High Probability Areas:
* Mass Airflow Sensor (MAF) Sensor: This sensor measures the amount of air entering the engine. A faulty MAF sensor can send incorrect readings, leading to a rich fuel mixture (too much gas). Clean the sensor with MAF sensor cleaner (following the cleaner's instructions carefully). If cleaning doesn't resolve the issue, replacement is likely needed.
* Throttle Position Sensor (TPS): This sensor tells the computer the throttle's position. A faulty TPS can cause incorrect fuel delivery. Check for proper voltage at the sensor using a multimeter and compare it against factory specifications found in a repair manual. Replacement might be necessary.
* Fuel Pressure Regulator: This regulator maintains the correct fuel pressure in the fuel rail. A malfunctioning regulator could allow too much fuel into the system. Testing fuel pressure with a gauge is crucial here. Should be tested both at idle and at higher RPM.
* Vacuum Leaks: A vacuum leak can cause the engine to run rich, as it disrupts the air/fuel ratio. Inspect all vacuum lines and connections for cracks or loose fittings. Pay close attention to lines connected to the intake manifold, brake booster, and emission control systems. A simple visual inspection often isn't enough; you might need to use a vacuum gauge to pinpoint leaks.
Medium Probability Areas:
* Fuel Injectors: While less likely if the other components are functioning correctly, faulty fuel injectors can cause a rich condition. Testing fuel injector flow rates requires specialized equipment. This is usually better left to a professional mechanic.
* Computer (ECM/PCM): Though rare, a faulty engine control module can cause incorrect fuel delivery. This is usually diagnosed by comparing sensor readings to what the computer is doing based on those sensor inputs. It's a difficult diagnosis and often requires professional tools and knowledge.
Low Probability Areas (after checking the above):
* Fuel Pump: A faulty fuel pump might deliver too much fuel under certain conditions. This is less likely to be the primary cause if the pressure test reveals correct pressure.
Troubleshooting Steps:
1. Check Engine Light (CEL): If the CEL is on, retrieve the diagnostic trouble codes (DTCs) using an OBD-II scanner. This will give you a better starting point for diagnosis. Keep in mind that OBD-II wasn't fully standardized in 1994, so a generic scanner might not read all codes. A scanner specific to GM vehicles from that era would be ideal.
2. Visual Inspection: Carefully inspect all vacuum lines, connectors, and hoses. Look for cracks, leaks, or loose connections.
3. Start with the MAF and TPS: These are common culprits and relatively easy to check and replace.
4. Fuel Pressure Test: This is essential to rule out a problem with the fuel pressure regulator or fuel pump.
5. Professional Diagnosis: If you're not comfortable performing these tests or replacing parts, take your Bravada to a trusted mechanic. They'll have the tools and expertise to properly diagnose and repair the issue.
Remember safety first! Always disconnect the negative battery terminal before working on any electrical components. Also, be aware of hot exhaust components when working under the hood. A repair manual specific to your 1994 Oldsmobile Bravada will be incredibly helpful throughout this process.
