1. Fuel Delivery Issues:
* Fuel Pump: A weak fuel pump might not deliver enough fuel at idle, but can manage it under load (when you pump the gas). Listen carefully for the fuel pump whirring when you turn the key to the "on" position (before cranking). A weak pump will make a weak or sputtering sound. Replacing the fuel pump is a common fix for this symptom.
* Fuel Filter: A clogged fuel filter restricts fuel flow, similar to a weak pump. This is a cheap and easy part to replace, so it's always worth checking.
* Fuel Pressure Regulator: This regulator maintains the correct fuel pressure in the system. A faulty regulator could be letting pressure drop too low at idle. Testing fuel pressure is needed to diagnose this. A mechanic can typically do this easily.
2. Idle System Problems (Carbureted Engine - Assuming your '84 Delta 88 is carbureted):
* Idle Air Control (IAC) Valve (if equipped): This valve controls the amount of air entering the engine at idle. If it's dirty or malfunctioning, the engine might stall. Cleaning it (carefully) is often a successful fix, otherwise replacement is necessary.
* Choke: If your carburetor has a choke, it might be sticking or not fully opening at operating temperature. The engine needs sufficient air/fuel mixture at idle. Manual adjustment and/or carburetor cleaning may be necessary.
* Carburetor itself: The carburetor might need a rebuild or replacement. This is a more involved repair and usually requires a mechanic or someone with carburetor expertise. Dirty jets, worn out parts, or incorrect adjustments are common causes.
3. Ignition System (Less Likely but Possible):
* Distributor Cap and Rotor: Worn or corroded distributor cap and rotor can cause poor ignition at low RPM (idle), but usually lead to more erratic running across the RPM range.
* Ignition Coil: A weak ignition coil might struggle to provide enough spark at idle.
Troubleshooting Steps:
1. Check the fuel filter: This is the easiest and cheapest first step.
2. Listen for the fuel pump: As described above.
3. Check the spark plugs and wires: Make sure they are properly connected and not damaged.
4. Clean the IAC valve (if applicable): This is a relatively simple process, often involving removing the valve and cleaning it with carburetor cleaner. Look up a YouTube video specific to your year and engine.
5. Inspect the carburetor (if applicable): Look for obvious signs of dirt, damage, or leaks. A professional cleaning or rebuild is likely necessary if something is wrong here.
6. Have fuel pressure tested: This is best left to a mechanic.
Important Considerations:
* Year and Engine: Knowing the exact engine (e.g., 307, 350) in your Delta 88 will help narrow down potential issues. Different engines have different systems.
* Mechanic: If you're not comfortable working on your car, it's best to take it to a qualified mechanic. They have the tools and expertise to diagnose and fix the problem efficiently and correctly.
Starting with the simpler checks (fuel filter, fuel pump sound) and gradually moving to more involved repairs is the most efficient approach. Remember safety first – disconnect the negative battery terminal before working on any electrical components.
