Surges/Chuggles

SYMPTOM DESCRIPTION:

Engine power variation, under steady throttle or cruise. Feels like the vehicle speeds up and slows down, with no change in the accelerator pedal.




SYSTEM OR COMPONENT TO CHECK ACTION

COMPUTER INPUTS/OUTPUTS CHECK: - OXYGEN SENSOR (O2) - Inspect sensor for
silicon contamination from fuel, or use of
improper RTV sealant.
The sensor will have a white, powdery coating,
and will result in a high but false signal
voltage (rich exhaust indication). The ECU/MCU
will then reduce the amount of fuel delivered
to the engine, causing a severe driveability
problem.
- ECU/MCU grounds for being clean,
tight, and in their proper location.
NOTE: - Use a "Scan" tool to make sure reading
of CPS matches vehicle speedometer. If
the CPS does not match the speedometer
speed, go to COMPONENT TESTS.




FUEL NOTE: - To determine if the condition is caused
by a rich or lean system, the vehicle should be
driven at the speed of the complaint.
CHECK: - FUEL PRESSURE
- FUEL INJECTOR BALANCE TEST.
- IN-LINE FUEL FILTER.




IGNITION CHECK: - Proper ignition voltage output with
appropriate spark tester.
- Spark plugs, wet plugs, cracks, wear, improper
gap, burned electrodes or heavy deposits.
- IGNITION TIMING.




EMISSIONS CHECK: - EGR SYSTEM.
NOTE: - Refer to EMISSION CONTROLS
for complete testing procedures.





ENGINE CHECK: - Vacuum lines for kinks and leaks.
- Generator output voltage. Repair if less than
9 or greater than 16 volts.