1. Fuel System:
* Throttle Position Sensor (TPS): A faulty TPS can cause a rough idle and stalling when accelerating. The engine computer relies on the TPS to determine the correct fuel and air mixture. A bad sensor gives incorrect information, leading to poor performance. This is a HIGH probability given your symptoms.
* Mass Air Flow Sensor (MAF): Similar to the TPS, a dirty or malfunctioning MAF sensor provides inaccurate readings of the air intake, leading to a poor fuel mixture. Clean the MAF sensor with MAF sensor cleaner (available at auto parts stores) – be gentle and avoid touching the sensor element. If cleaning doesn't help, it likely needs replacement.
* Fuel Filter: A clogged fuel filter restricts fuel flow, causing rough idling and stalling, especially under load. Replace the fuel filter. It's a cheap and easy first step.
* Fuel Pump: A weak fuel pump might not deliver enough fuel, especially when the engine is under load (when you press the gas). This would manifest as rough idle and stalling when accelerating. Check the fuel pressure with a fuel pressure gauge.
* Fuel Injectors: Clogged or malfunctioning fuel injectors can cause inconsistent fuel delivery, resulting in a rough idle and stalling. This is less likely to cause immediate stalling upon acceleration, but could contribute to the rough idle. Requires specialized tools and knowledge to test.
2. Ignition System:
* Distributor Cap and Rotor: Worn or corroded distributor cap and rotor can cause misfires and poor engine performance, leading to a rough idle and stalling. Inspect for cracks, corrosion, or excessive wear.
* Ignition Coil: A weak or failing ignition coil can't provide sufficient spark, leading to misfires and similar symptoms. This is less likely to cause immediate stalling upon acceleration, but contributes to rough idle.
* Spark Plugs and Wires: Worn or fouled spark plugs and damaged spark plug wires can also cause misfires. Inspect them and replace if necessary.
3. Vacuum Leaks:
* Vacuum leaks in the intake system can disrupt the air/fuel mixture, causing rough idling and stalling. Inspect all vacuum hoses and connections for cracks or loose fittings.
Troubleshooting Steps:
1. Check for trouble codes: Use an OBD-II scanner (available at auto parts stores) to read any trouble codes stored in the car's computer. This can pinpoint the problem area.
2. Visual Inspection: Check for obvious issues like loose connections, vacuum leaks, damaged wires, or anything out of place.
3. Start with the easy/cheap fixes: Replace the fuel filter and clean the MAF sensor.
4. Test the fuel pressure: Rent or borrow a fuel pressure gauge to measure the fuel pressure.
5. Check the TPS: This is a very likely culprit. You can test this with a multimeter, or replace it as it is relatively inexpensive.
Important Note: If you're not comfortable working on cars, it's best to take your Cutlass Supreme to a qualified mechanic. Improperly diagnosing and repairing these issues could lead to further damage. The TPS is a good starting point for a DIYer though, as it's relatively easy to access and replace.
