Second Chance Garage
All About Car Restoration
Second Chance Garage
All About Car Restoration


1953-1960 Classic Car Engines Troubleshooting Guide: Rough Idle

Things to Look For:

The term "rough idle" means that the engine does not run smoothly when idling. The most likely cause is an over-rich mixture but any defect which produces uneven explosions or missing will cause a rough idle. The most common causes are:

  1. Dirty idle jets and passages.
  2. Rich idle adjustment.
  3. Dirty air cleaner.
  4. Float level too high.
  5. Choke set too rich.
  6. Fuel volatility too high or too low.
  7. Substantial air leak into intake manifold.
  8. Fuel pump pressure too high or too low.
  9. Clogged carburetor jets.
  10. Ignition point gap too narrow or much too wide.
  11. Spark plug gaps too narrow or too wide.
  12. Sticking breaker arm.
  13. Weak spark which permits some missing.
  14. Leaky engine valve.
  15. Sticking valve or rocker.
  16. Broken valve spring.
  17. Insufficient tappet clearance.
  18. Hydraulic tappet holds valve open

The Complete Guide to Troubleshooting 1953-1960 Era American Classic Car Engines

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