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P0300-MULTIPLE CYLINDER MIS-FIRE —
TEST
7
NOTE: Before continuing visually and physically inspect the fuel delivery
system for external leaks or damage. Repair /replace as necessary.
Turn the ignition off.
WARNING: The fuel system is under a constant pressure even with the
engine off. Before testing or servicing any fuel system hose, fitting or line,
the fuel system pressure must be released.
Install special tool #6539 (5/16 ) fuel line adapter.
Install the fuel pressure gauge.
Start the engine and allow the fuel system to reach maximum pressure.
Turn the ignition off.
NOTE: Fuel specification is 400 KPa +/- 34 KPa (58 psi +/- 5 psi).
Using special tool #C4390, Hose Clamp Pliers, pinch the rubber fuel line between the
fuel pressure gauge and the engine.
Monitor the fuel pressure gauge for a minimum of 5 minutes.
NOTE: The pressure should not fall below 241 KPa (35 psi)
Does the Upstream gauge fall below the above specification?
Yes → Replace the leaking Fuel Injector(s).
→ Go To 8
No
8
Warning: The fuel system is under a constant pressure (even with the engine
off). Before testing or servicing any fuel system hose, fitting or line, the fuel
system pressure must be released.
CAUTION: After each Fuel Injector actuation, start the engine to clean the
cylinder of fuel. Failure to do so could cause engine damage.
Remove special tool #C4390.
Start the engine and allow the fuel pressure to reach maximum pressure.
Ignition on, engine not running.
Using the DRBIII , actuate the Fuel Injector for the cylinder that indicated the
misfire.
Monitor the fuel pressure gauge.
Does the fuel pressure gauge indicate a drop in fuel pressure?
Yes → Go To 9
→ Go To 10
No
NOTE: Turn the ignition off, remove the fuel pressure gauge, and connect
the fuel lines before continuing.
9
Check for any of the following conditions/mechanical problems.
ENGINE VACUUM - must be at least 13 inches in neutral
ENGINE VALVE TIMING - must be within specifications
ENGINE COMPRESSION - must be within specifications
ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks.
ENGINE PCV SYSTEM - must flow freely
TORQUE CONVERTER STALL SPEED - must be within specifications
POWER BRAKE BOOSTER - no internal vacuum leaks
FUEL - must be free of contamination
CAM LOBES - must not be worn excessively
CYLINDER LEAKAGE TEST - must be within specifications
VALVE SPRINGS - cannot be weak or broken
Are there any engine mechanical problems?
Yes → Repair as necessary.
→ Go To 17
No
ACTION
Perform POWERTRAIN VERIFICATION TEST VER - 5.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
DRIVEABILITY - GAS
Continued
99
APPLICABILITY
All
All
All
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