Checks
| Actions
|
DEFINITION: Fuel ignites in the intake manifold, or in the exhaust system,
making loud popping noise.
|
Preliminary Checks
|
| • | Refer to
Symptoms ,
Important
Preliminary Checks Before Starting.
|
| • | Check PCM grounds for being clean, tight and in their proper locations.
Refer to
PCM wiring diagrams in Electrical Diagnosis.
|
|
Fuel System
|
| • | Check each injector harness is connected to the correct injector/cylinder
according to the firing order (firing order: 1-8-4-3-6-5-7-2).
Relocate injector harnesses as necessary. |
|
Sensor/System
|
| • | Check Secondary Air Injection (AIR) system. |
| • | Check Air intake system and crankcase for air leaks. |
| • | Check Crankcase ventilation valve for proper operation. Place finger
over inlet hole in valve end several times. Valve should snap back. If not, replace
valve. |
| • | Check for proper calibration of speedometer. Connect Signal Generator
(J 33431-B) to VSS electrical connector. Ignition ON, tester ON and monitor
the speedometer. The speedometer should indicate 86 km/h (54 mph). Refer to
8A (Cell 33)
. |
| • | Using a Scan Tool, monitor TP sensor voltage. The TP sensor voltage should
be less then 0.9 volt. If the TP sensor voltage is greater than 0.9 volt, inspect
the ASR/TCS adjuster assembly (If so equipped). Also inspect throttle body and accelerator
cables for binding. Refer to
Adjuster Assembly Throttle And Cruise
Control Cables.
|
| • | Check the EGR system for proper operation. |
|
Ignition System
|
| • | Check for proper ignition voltage output with spark tester J 26792.
Refer to Distributor Ignition System for procedure. |
| • | Check for an intermittent ignition system malfunction in the following
circuits: |
| - | Intermittent Low resolution circuit. |
| - | Intermittent High resolution circuit. |
| - | Intermittent Ignition Control circuit. |
| - | Using the scan tool's Snapshot feature may help locate an intermittent
ignition failure. Review low and high resolution signals. Abnormal low and high resolution
signals can cause a backfire on acceleration. Refer to
Distributor Ignition (DI) System Check . |
| • | Remove spark plugs and check for the following: |
| • | An improper spark plug gap will cause a driveability problem. Refer to
spark plug gap specification is Section OB. 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. Refer to
DTC P0172 Fuel Trim System Rich Bank 1
and
DTC P0175 Fuel Trim System Rich Bank 2 to determine the Rich condition or
Engine Mechanical
for the oil fouling condition. |
| • | Visually/Physically inspect Secondary ignition for the following: |
| - | Ignition wires for cross firing. |
| - | Ignition wires arcing to ground. |
| - | Ignition wires for proper routing. |
| - | Distributor cap for cracks or carbon tracking. |
| • | 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. |
|
Engine Cooling System
|
| • | Check engine coolant level for being low. Refer to
Engine Cooling.
|
| • | Check engine thermostat for having a faulty part or for wrong heat range.
Refer to
Engine Cooling
. |
|
Engine Mechanical
|
| • | Check engine mechanical: |
| - | Sticking or leaking valves. |
| - | Excessive oil in combustion chamber-Leaking valve seals. |
| - | Low cylinder compression. |
| • | For incorrect basic engine parts. Inspect the following: |
| • | Refer to
Engine Mechanical
for diagnosis
procedures. |
|
Additional Checks
|
| • | Visually (physically) check: Vacuum hoses for splits, kinks, and proper
connections and routing as shown on Vehicle Emission Control Information label. |
| • | Check Intake and exhaust manifold(s) for casting flash. Refer to
Engine Mechanical
. |
| • | Check TCC operation. The scan tool should indicate an RPM drop when
the TCC is commanded ON. Refer to
Transmission Control Systems.
|
| • | Check exhaust system for possible restriction. Check the following: |
| - | Inspect exhaust system for damaged or collapsed pipes. |
| - | Inspect mufflers for heat distress or possible internal failure. |
| - | For possible plugged Three-Way catalytic converters by comparing
exhaust system back pressure on each side of engine. Check back pressure by removing
AIR check valves near exhaust manifolds. Refer to Restricted Exhaust System Check
and Exhaust System. |
| • | An engine miss condition can be caused by Electromagnetic Interference
(EMI) on the reference circuit. EMI can usually be detected by monitoring engine
RPM with a scan tool. A sudden increase in RPM with little change in actual engine
RPM change, indicates EMI is present. If a problem exists, check routing of secondary
ignition wires, high voltage components (Near Ignition Control circuits). Check distributor
ground circuit for being open or loose. |
| • | Is Traction Control Adjuster Assembly out of adjustment? Refer to
Adjuster Assembly-Throttle And Cruise Control Cables.
|
| • | Check PNP switch circuit . Refer to
Park/Neutral Position Switch Check , or
use the Tech 1 and be sure the scan tool indicates vehicle is in drive with gear
selector in drive or overdrive. |
| • | Check for faulty motor mounts. Refer to
Engine Mechanical
for inspection of mounts. |
| • | Check for intake and exhaust manifold passages for casting flash. Refer
to
Engine Mechanical.
|
|
