Warm engine surges


Warm engine surges (speed of car changes or varies while driving)

Diagnosis Procedure

  1. Check fuel quality
    • Poor fuel quality can cause a less combustible mixture and a possible engine surge.
  2. Check for air leaks
    • Loose connections or cracked hoses between the fuel tank and injection pump may result in air in the fuel system. Air trapped in injectors or lines can cause an engine to surge at driving speeds.
  3. Check for fuel leaks
    • Fuel leaks at fuel lines and fuel delivery valves reduce fuel pressure and effect delivery to the injectors.
  4. Check injection pump mounting brackets
    • Loose pump mounting brackets can cause pump misalignment and injection timing change, resulting in an engine surge at driving speeds.


Quality check

  1. Start engine, allow to warm up and observe idle quality
    • engine should idle smoothly
  2. With correct tire pressure, drive car on a level road Accelerate to a constant speed of 35 MPH
    • in 3rd gear (4-speed transmission)
    • in 4th gear (5-speed transmission)
  3. Accelerate again to full throttle and note the acceleration quality.
    • engine should accelerate evenly engine should not surge
  4. Maintain steady speed and observe performance quality
    • engine should maintain even performance at all speeds and show no symptoms of surging.

If test passed, return car to customer

If test failed, perform diagnosis III