Checks
| Action
|
DEFINITION: Steady
pulsation or jerking that follows engine speed, usually more pronounced
as the engine load increases.
|
Preliminary
|
| • | Check the intake air system for the following conditions: |
| - | Dirty or damaged air filter element |
| - | Damaged or disconnected intake air ducting |
|
Sensor/System
|
| • | Check the mass air flow (MAF) sensor and connections. |
| • | Check the engine coolant temperature (ECT) sensor for being shifted
in value. Connect the scan tool and compare the engine coolant temperature
with the intake air temperature (IAT) on a cold engine. The
ECT and IAT should be within ±3°C (5°F)
of each other. Check the resistance of the ECT sensor if the
temperature is out of range with the IAT sensor. Refer to
Temperature Versus Resistance
for specifications. |
| • | Check the throttle position (TP) sensor and connections. |
| • | Check for throttle body tampering, excessive deposits, or damage. |
| • | Check the exhaust gas recirculation (EGR) system for proper operation. |
|
Fuel
System
|
| • | Check the fuel pressure. |
| • | Check the fuel injectors and related wiring. |
| • | Check for fuel in the fuel pressure regulator. |
| • | Check for items that can cause an engine to run rich and/or lean. |
|
Ignition
System
|
| • | Check the crankshaft position (CKP) sensor A and B for
proper operation. |
| • | Check the ignition control (IC) circuits at each ignition module
assembly for poor connections, damage, misrouting. |
| • | Check the ignition coils for damage. |
| • | Check the spark plug boots for misalignment, and damage. |
| • | Check for a damaged or missing ground spring at each ignition
module assembly. |
|
Engine
Cooling
|
| • | Check for an incorrect, damaged, or malfunctioning thermostat.
Refer to
Thermostat Diagnosis
in Engine Cooling. |
|
Engine
Mechanical
|
| - | Sticking or leaking valves |
| - | Excessive oil in the combustion chamber-leaking valve seals |
| • | Check for incorrect basic engine parts. Inspect the following: |
|
Additional
Checks
|
| • | Inspect the vacuum hoses for splits, kinks, proper routing and
connections, and/or damage. Refer to the Vehicle Emission Control
Information label. |
| • | Check the exhaust system for possible restrictions. |
| • | An engine miss condition can be caused by electromagnetic interference
(EMI). EMI can usually be detected by monitoring the engine RPM with
a scan tool. A sudden increase in RPM with little change in
the actual engine RPM, indicates EMI is present. |
|
