Warm Engine Lacks Power and / or Smokes Excessively

Symptom:

Warm engine lacks power and/or smokes excessively

Diagnosis Procedure

There is no preliminary diagnosis procedure for cars with this symptom. For the symptom warm engine lacks power and/or smokes excessively, go directly to Diagnosis III, below:

 

  1. Check for crankshaft bolt modification on 1.5L engines
  2. Check air filter
  3. Check valve clearance
  4. Check compression
  5. Check injectors
  6. Perform injection system tests*

*Warm running problems are affected by valve timing, spur belt tension, cold start advance, injection pump timing, idle RPM and maximum RPM. Therefore all of these items should be checked to assure that all factors that could affect vehicle performance are adjusted properly.

Quality check

Except 1981 – 82 Rabbit/Jetta

  1. Start engine, allow to warm up and observe idle quality.
    • the idle speed is corrupt
    • engine should idle smoothly
    • the idle speed should not vary more than 50 RPM
  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 from 35 MPH to 55 MPH
    • engine should accelerate evenly
    • engine should not lack power or smoke
  4. Maintain steady speed and observe performance quality.
    • engine should maintain adequate performance at all speeds and show no symptoms of loss of power or smoke

1981 – 82 Rabbit/Jetta

  1. Start engine, allow to warm up and observe idle quality.
    • the idle speed is correct
    • engine should idle smoothly
    • the idle speed should not vary more than 50 RPM
  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 time it takes to reach 55 MPH.
    • should be 16.1 seconds maximum (4-speed transmission)
    • should be 18.6 seconds maximum (5-speed transmission)

If test passed, return car to customer

If test failed — if diagnosis I and II have been completed, Replace injection pump — except 1981 – 82 Rabbit/Jetta; see below:

 

Because of variations in fuel quality (cetane rating) and production tolerances, the injection timing on some 1981-82 Rabbit, Pick-up and Jetta’s may have to be changed to 0.98 + 0.05mm if the engine

  • Lacks power and/or smokes excessively
  • Engine misfires
  • Engine surges

The injection timing procedure can only be changed after both diagnosis procedure I and diagnosis procedure II have been completed.