Backfire. Chevrolet Monte Carlo 2002

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2002 🢒 Monte Carlo 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Backfire

Checks

Actions

DEFINITION: Fuel ignites in the intake manifold, or in the exhaust system, making loud popping noise.

Preliminary Checks

•	Refer to Diagnostic System Check - Engine Controls .

•	Refer to Important Preliminary Checks.

•	Refer to Visual/Physical Checks.

•	Search for bulletins.

Sensor/System

•	Test for the following intermittent ignition system conditions:

-	Intermittent CKP 18X signal

-	Intermittent ignition feed circuit or sensor ground circuit to the crankshaft position sensor or the camshaft position sensor

-	Intermittent 3X reference signal

-	Intermittent camshaft position signal

•	Inspect the mass air flow (MAF) sensor conditions. Ensure that the MAF sensor honeycomb is not damaged.

Fuel System

•	Test for low fuel pressure. Refer to Fuel System Diagnosis .

•	Test for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

•	Ensure each injector harness is connected to the correct injector/cylinder.

Ignition System

•	Test for proper ignition voltage output using the following steps:

-	Clip the J 26792 Spark Tester to engine ground.

-	Connect one end of a spark plug wire to the spark tester. Leave the other end of the spark plug wire connected to the coil being tested.

-	Connect another spark plug wire between the remaining coil tower on the coil being tested and ground.

-	Crank the engine while observing the spark tester. A crisp blue spark should be observed.

-	Repeat the above steps for each coil.

•	If spark is not present at the coils, test for the following conditions:

-	Coils--Cracks, carbon tracking/arcing, or a secondary resistance value outside the specified range

Coil Resistance
5,000-8,000 ohms

-	Spark plug wires--Signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range

Spark Plug Wire Resistance
9,840 ohms per meter (3,000 ohms per foot)

Important: Spraying the secondary ignition wires with a light mist of water may help locate an intermittent problem. Ignition components will arc to ground when a secondary component is faulty.

-	Defective module

-	Ignition system wiring--Loose ignition module feed or ground connection, or damaged system wiring

•	Remove spark plugs and inspect for the following:

-	Fouled plugs

Cracks

Wear

-	Improper gap

-	Burned or damaged electrodes

-	Improper heat range or reach

•	If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.

Engine Mechanical

Test and inspect engine mechanical:

•	Check compression

•	Sticking or leaking valves

•	Worn camshaft lobes

•	Valve timing

•	Bent push rods

•	Worn rocker arms

•	Broken valve springs

•	Excessive oil in combustion chamber--Leaking valve seals

•	Low cylinder compression

•	For incorrect basic engine parts--Inspect the following:

Camshaft

-	Cylinder heads

-	Pistons, etc.

•	Refer to Engine Mechanical for diagnosis procedures.

Additional Checks

•	Inspect Intake and exhaust manifolds for casting flash.

•	Test torque converter clutch (TCC) operation. Refer to Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission .

•	Test exhaust system for possible restriction. Inspect the following:

-	The exhaust system for damaged or collapsed pipes

-	The mufflers for heat distress or possible internal failure

-	For possible plugged three-way catalytic converter--Refer to Restricted Exhaust in Engine Exhaust.