1. Vacuum leaks: Check the car for vacuum leaks. They can cause the car to run lean and cause rough idle.
2. Fuel pressure: Check the fuel pressure to ensure it is within specifications. Low fuel pressure can cause the car to run rough and have a drop in revs.
3. Ignition system: Check the ignition system, including the spark plugs, spark plug wires, and distributor cap and rotor. Worn or faulty ignition components can cause rough idling and a drop in revs.
4. Throttle body: Clean the throttle body and check the throttle position sensor. A dirty throttle body or a faulty sensor can cause the car to run rough and have a drop in revs.
5. Idle air control valve (IAC): Check the IAC valve. A faulty IAC valve can cause the car to run rough and have a drop in revs.
6. Oxygen sensor: Check the oxygen sensor. A faulty sensor can cause the car to run rich or lean and cause a drop in revs.
7. Fuel Filter: Check the fuel filter and replace if necessary. A clogged fuel filter can restrict fuel flow and cause a drop in revs.
8. Fuel Lines: Check the fuel lines for any kinks or obstructions. A kinked fuel line can restrict fuel flow and cause a drop in revs.
It is recommended to take the car to a qualified mechanic for further diagnosis and repairs.
