The engine idles too fast
Symptom: The engine idles too fast. After the engine has run long enough to be warm, the idle speed does not come down to normal. You really notice it when you come to a stop and must have to push hard on the brake pedal to keep the car from moving.
1. If you have a carburetor, you may have a bad accelerator pump or power circuit.
The Fix: Replace accelerator pump or replace carburetor.
2. The engine may be overheating.
The Fix: Check and repair cooling system.
3. The fuel pressure regulator may be operating at too low a pressure.
The Fix: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (Generally not a DIY job)
4. The ignition timing may be set wrong.
The Fix: Adjust ignition timing.
5. There may be some type of ignition problem.
The Fix: Check and replace distributor cap, rotor, ignition wires and spark plugs.
6. There may be a fault in the computerized engine control system.
The Fix: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)
7. There may be a vacuum leak.
The Fix: Check and replace vacuum lines as required.
8. You have a bad idle speed control unit.
The Fix: Replace idle speed control unit.
9. The alternator may not be working properly.
The Fix: Replace alternator.