Checks
| Action
|
DEFINITION: Engine
power variation under steady throttle or cruise. Feels like the vehicle speeds
up and slows down with no change in the accelerator pedal.
|
Preliminary
|
| • | Refer to Symptoms, Important Preliminary Checks Before Starting. |
| • | Check PCM grounds for being clean, tight and in their proper locations. |
| • | Be sure driver understands transmission torque converter clutch,
and A/C compressor operation as explained in the owners manual. Inform customer
how TCC and the A/C clutch operates. |
|
Sensor/System
|
| • | Check Heated Oxygen Sensors (HO2S). The Heated Oxygen Sensors
(HO2S) should respond quickly to different throttle position, if they do not,
check the HO2S for silicon or other contaminates from fuel, or use of improper
RTV sealant. The sensors may have a white powdery coating and result in
a high but false signal voltage (rich exhaust indication). The PCM will
then reduce the amount of fuel delivered to the engine causing a severe
driveability problem. |
| • | Check MAF connections. Repair or replace terminals. Refer to Electrical Diagnosis
for wiring repair procedures. |
| • | Check the EGR system for proper operation. |
|
Fuel System
|
| • | Check for low fuel pressure. Refer to the Fuel System Pressure Check.
|
| • | Check for restricted fuel filter. |
| • | Check for contaminated fuel. Refer to Fuel
Quality Diagnosis
. |
| • | Check each injector harness is connected to the correct injector/cylinder
according to the firing order. Relocate injector harnesses as necessary. |
| • | Check items which can cause an engine to run rich (long term fuel
trim near - 99%). |
| • | Check items that can cause an engine to run lean (long term fuel
trim near 100%). |
|
Ignition System
|
| • | Wetting down the secondary ignition system with water from a spray
bottle may help locate damaged or deteriorated components. Look/listen for
arcing or misfiring as water is applied. |
| • | Check for proper ignition voltage output with spark tester J 26792.
Refer to Secondary Ignition System Diagnosis
. |
| • | Remove spark plugs and check for the following: |
| • | An improper spark plug gap will cause a driveability problem.
The spark plug gapping should be done using a wire gauge gap tool (J 41319).
Refer to Spark Plug Replacement. If spark plugs are gas or oil fouled,
the cause of the fouling must be determined before replacing the spark
plugs. |
| • | Check for loose ignition control module ground. |
| • | Spark plugs for proper heat range. Refer to Owners Manual or General Information.
|
|
Additional Checks
|
| • | Visually (physically) check: Vacuum hoses for splits, kinks, and
proper connections and routing as shown on Vehicle Emission Control Information
label. |
| • | Check TCC operation. Refer to Transmission
Controls.
|
| • | Check for a restrictive exhaust system. Refer to Restricted Exhaust System Check.
|
|
