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When Engine is Hot

This condition usually caused by an over-supply of fuel due to any of the items listed under Engine Won't Start Due to Excessive Fuel Supply. In rare cased, an ignition coil may lose it's efficiency when it is hot and cause ignition failure.

When Engine is Cold

Many of the conditions enumerated under Engine Won't Start also may cause hard starting in cold weather. Of particular importance, however, are the following:

Proper Engine Ventilation

PCV Control of Engine Emissions

Many hobbyists have long loathed "Emissions Control Systems". For the "Muscle Car" enthusiasts, the advent of "Emissions Control Standards" has meant poor performance and equipment restrictions. Recent legislation in California ended the "Smog Check" requirements for 1973 and older vehicles in favor of voluntary compliance.

Owners are still required to keep their factory-installed emissions systems intact, but these vehicles are no longer subject to periodical inspection for compliance. And, as you might expect, many enthusiasts have mistakenly interpreted this legislation. This has lead to the removal of emissions control equipment in an effort to improve engine operation and performance.

Much of the pre-1972 "hang-on" emission systems did little to effect engine performance. Much of the effected performance was due to the drop in compression and the switch to lower octane fuels. Design changes, such as "Lean-Burn" concepts through cam re-design, severally effected engine performance. But, to many, the added emissions equipment was to blame and that thinking has not changed much over time.

Discover the main causes of engine misfires in this article.

It should be noted that the altitude at which the car is operated has a decided effect on performance. A car adjusted for normal altitudes will lack performance at high altitudes, whereas a car which operated normally at high altitudes may have a lean carburetor adjustment and show signs of pre-ignition when operation at sea level.

• Broken part in the dive line anywhere from clutch to rear axle shaft.
• No oil or not enough oil in fluid coupling or torque converter.
• Some defect in automatic transmission causes binding or dragging of clutches or slipping bands.
• Engine develops only enough power to run itself due to:
  
  • (a) extremely lean or rich mixture;
    
  • (b) excessive engine friction;
    
  • (c) throttle does not open;
    
  • (d) very dirty air cleaner;
    
  • (e) clogged exhaust system.
• Oil in fluid coupling or torque converter is semi-solid due to zero temperature. This trouble is unlikely if the recommended oil is used.

Pre-ignition mean that the mixture is set on fire before the spark occurs, being ignited by a red hot spot in the combustion chamber such as an incandescent particle of carbon; a thin piece of protruding metal; an overheated spark plug, or a bight red hot exhaust valve. The result is reduction of power and overheating accompanied by pinging. The bight red hot exhaust valve may be due to a leak, to lack of tappet clearance, to valve sticking, or a weak or broken spring.

Pre-ignition may not be noticed if not severe. Severe pre-ignition results in severe pinging. The commonest cause of pre-ignition is a badly overheated engine. When the engine won't stop when the ignition is shut off, the cause is often due to red hot carbon particles resting on heavy carbon deposit in a very hot engine.