P0308 on 2006-2007 Chevrolet Malibu SS: Cylinder 8 Misfire Causes and Fixes

What's Unique About the 2004-2011 Chevrolet MALIBU

This code is highly specific because the only Malibu model in this year range with a V8 engine was the 2006-2007 Malibu SS, which featured a transversely mounted 5.3L LS4 V8. This front-wheel-drive V8 configuration is unusual. Unlike many other GM V8s from this era, the common Active Fuel Management (AFM) lifter failures are less of a direct concern for this specific code, as cylinder #8 was not an AFM-managed cylinder. AFM (also called DOD) in the LS4 deactivates cylinders 1, 4, 6, and 7 under light load to improve fuel economy. However, general valvetrain issues or oiling problems related to the AFM system can still potentially affect non-AFM cylinders.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Generation note: The 2004-2011 range covers the 6th (2004-2007) and 7th (2008-2012) generations. However, code P0308 is only possible on the V8-equipped Malibu SS, which was exclusively produced from 2006-2007 as part of the 6th generation.

Symptoms You May Notice

• Rough or shaking idle.
• Hesitation or stumbling during acceleration.
• Noticeable loss of engine power.
• Solid or flashing Check Engine Light.
• Potential fuel smell from the exhaust due to unburnt fuel.
• Decreased fuel economy.

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability → Shop Ignition Coil Coil-on-plug systems are a common failure point on many vehicles, and heat in the engine bay can shorten their lifespan. The LS4 uses individual coils for each cylinder.
   How to confirm: Swap the ignition coil from cylinder 8 with another cylinder (e.g., cylinder 6). Clear the codes and drive the vehicle. If the code changes to P0306, the ignition coil is faulty. This is a definitive and free diagnostic step.
   Typical fix: Replace the faulty ignition coil. It's often recommended to replace the spark plug at the same time.
   Est. part cost: $30-$75
2. Worn Spark Plug 🔴 High Probability → Shop Spark Plug Spark plugs are a regular maintenance item with a finite lifespan. A worn electrode, excessive carbon fouling, or cracked insulator will cause a weak or inconsistent spark, leading to a misfire.
   How to confirm: Remove the spark plug from cylinder 8 and inspect it. Look for heavy carbon fouling, oil contamination, or a worn/damaged electrode. Compare it to a new plug or a plug from a known good cylinder.
   Typical fix: Replace the spark plug. It is best practice to replace all 8 spark plugs at the same time to ensure consistent performance and avoid future misfires.
   Est. part cost: $5-$20 per plug
3. Bad Spark Plug Wire 🟡 Medium Probability → Shop Spark Plug Spark plug wires degrade over time due to high voltage and engine heat, causing cracks or increased internal resistance that weakens the spark.
   How to confirm: Visually inspect the wire for cracks, burns, or corrosion on the contacts. Use a multimeter to check its resistance; a reading outside of the manufacturer's specification (typically a few thousand ohms per foot) indicates a bad wire.
   Typical fix: Replace the faulty spark plug wire. It is often sold in a set for all cylinders.
   Est. part cost: $40-$80 for a set
4. Clogged or Failed Fuel Injector 🟡 Medium Probability → Shop Fuel Injector Fuel injectors can become clogged with deposits over time or fail electronically, preventing the correct amount of fuel from reaching the cylinder.
   How to confirm: Use a mechanic's stethoscope or a long screwdriver to listen to the injector. It should make a consistent clicking sound. Compare the sound of the cylinder 8 injector to a known good cylinder. You can also swap the injector with another cylinder, but this is more labor-intensive.
   Typical fix: Replace the faulty fuel injector. The fuel rail may need to be removed for access.
   Est. part cost: $50-$120

Rare But Worth Checking

• Low Cylinder Compression: This indicates a mechanical engine problem, such as a worn piston ring, a bad valve, a damaged piston, or a leaking head gasket. A compression test is needed to confirm this, which is a more involved diagnosis.
• Vacuum Leak: A leak in the intake manifold gasket near the runner for cylinder 8 can introduce unmetered air, causing a lean misfire. This is less common for a single-cylinder misfire but is possible.
• AFM/DOD Lifter Issues: → Shop Engine Valve Lifter While cylinder 8 is not an AFM cylinder, widespread issues with the AFM system, such as oil pressure problems or failing lifters on other cylinders, can sometimes cause issues that manifest elsewhere. 🎬 See how to diagnose misfires related to the AFM system. A user on a Chevrolet forum with a different engine reported a pitted exhaust valve lifter causing an intermittent misfire.

Diagnosis Steps

1. Confirm the P0308 code using an OBD-II scanner 🎬 Watch a simple explanation of the P0308 code and fixes. and check for any other stored codes. Note if the check engine light is flashing.
2. Locate cylinder #8. On the transversely mounted LS4 V8 🎬 Watch this walkthrough for replacing coils and plugs on the LS4., the bank closer to the radiator is Bank 2 (even numbers). The cylinders are numbered 2-4-6-8 from the passenger side (front of engine/accessory belts) to the driver's side. Cylinder 8 is the rearmost cylinder on the radiator side, closest to the driver.
3. Visually inspect the ignition coil, spark plug wire, and the area around cylinder 8 for any obvious damage, such as cracks, burns, or loose connections.
4. Swap the ignition coil from cylinder 8 with the coil from cylinder 6. Clear the codes, run the engine, and rescan. If the code changes to P0306, the coil is bad.
5. If the code remains P0308, swap the spark plug from cylinder 8 with another cylinder. If the code follows the plug, the plug is bad.
6. If the misfire still remains on cylinder 8, inspect and test the spark plug wire for resistance using a multimeter.
7. If the entire ignition system for cylinder 8 checks out, test the fuel injector by listening for its clicking operation.
8. If ignition and fuel seem okay, perform a cylinder compression test to check for mechanical engine problems like bad valves or piston rings.

Parts You'll Likely Need

• Ignition Coil (OEM #ACDelco D585 (GM 10457730)) — This is one of the most frequent failure points for a single-cylinder misfire. Heat and vibration cause the internal windings to fail over time. The D585 is a well-known, robust coil used on many LS engines.
  Trusted brands: ACDelco, Delphi, NGK
  OEM price range: $50-$75
  Aftermarket price range: $30-$55
• Spark Plug (OEM #ACDelco 41-110 (Iridium)) — As a standard wear item, a fouled or worn spark plug is a very common cause of misfires. The OEM recommended plug is Iridium for its longevity and performance.
  Trusted brands: ACDelco, NGK, Bosch
  OEM price range: $10-$20
  Aftermarket price range: $5-$15
• Spark Plug Wire Set — The insulation on wires breaks down over time, causing the spark to weaken or arc to ground before reaching the plug.
  Trusted brands: ACDelco, NGK
  OEM price range: $60-$90
  Aftermarket price range: $40-$80

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or starting to affect other cylinders, a P0300 (Random/Multiple Cylinder Misfire) code may appear alongside P0308.

Technical Service Bulletins (TSBs) & Recalls

• PIP5628G: A general technical service bulletin for diagnosing misfire codes (P0300-P0308) on 2011 model year GM vehicles, indicating a standardized diagnostic process.
• 07-06-04-019E: While this TSB is for code P2138 (Accelerator Pedal Position Sensor), it is relevant to the platform as it addresses electrical issues caused by water intrusion in the kick panel harness connector, which can cause various difficult-to-diagnose problems.

Platform-Specific Known Issues

• Access to the rear bank of cylinders (including #8) on the transversely mounted LS4 V8 can be tight, potentially making the repair more difficult than on a longitudinally mounted engine.
• Some owners report intermittent misfires under heavy load that can be difficult to diagnose, sometimes related to fuel delivery or even mechanical issues that only appear under stress.

Mechanic-Grade Diagnostic Values

• Ignition Coil Resistance (Aftermarket D585 style) — expected: Primary: ~0.660 ohms, Secondary: ~6.1k ohms. Failure: Readings significantly outside of these values.
• Cylinder Compression — expected: 120-150 PSI. Failure: A reading significantly below 120 PSI, or a large variance compared to other cylinders, indicates a mechanical engine issue.
• AFM System Oil Pressure (at relief valve) — expected: Regulated to approximately 55-60 PSI. Failure: If the valve sticks open, overall engine oil pressure can drop significantly, causing widespread issues.

Hidden / Shadow Codes Worth Checking

• Misfire Counters (No DTC): A professional scan tool like the GM Tech 2 can display a running count of misfire events per cylinder, even if the count is not high enough to trigger a P030x trouble code. This allows a technician to see minor or intermittent misfires that haven't yet illuminated the Check Engine Light. (see via View the misfire data list or graphical misfire display in a GM Tech 2 or equivalent advanced scan tool.)

Scan Tool Commands That Help

• GM Tech 2 (or equivalent): Crankshaft Position System Variation Learn (Crank Relearn) — This procedure should be performed after replacing a crankshaft position sensor, PCM, or flywheel/flexplate. It compensates for minor mechanical tolerances and improves the accuracy of misfire detection. It can resolve persistent random misfire codes (P0300) or false misfires when no mechanical fault is found.

Wiring & Ground Locations

• Cylinder 8 Fuel Injector Control — Pin J2-48 on the Engine Control Module (ECM) connector.. This pin, with a Light Blue/Red wire, is the specific circuit that the ECM uses to command the cylinder 8 fuel injector. A wiring fault here would directly affect cylinder 8.
• G102 — Located at the left rear of the engine.. This is the primary ground point for all eight ignition coils. A poor connection at G102 could cause weak or intermittent spark on multiple cylinders, including cylinder 8.
• Main Engine-to-Transaxle Ground — On a transaxle stud, often on a bell housing bolt, under the ignition control module area.. This is a primary power ground for the engine block. A loose or corroded connection here can cause a wide range of erratic electrical issues, including misfires that are difficult to diagnose.

Real Owner Repair Stories

• Reddit user in r/LSSwapTheWorld (Vehicle with LS4 engine) — Misfire on cylinders #5 and #7 that occurred from idle up to about 1,000 RPM, then seemed to disappear at higher RPM.
  ❌ Tried (didn't work) Initial diagnosis pointed towards common issues like spark plugs or wires.
  ✅ What actually fixed it The final cause was discovered to be broken valve springs on cylinders #5 and #7, which only allowed the valves to open slightly, causing poor compression at low RPMs.
• YouTube channel Southern Gearz (Vehicle with a 5.3L LS engine swap) — Persistent random misfire code (P0300) that was difficult to trace.
  ❌ Tried (didn't work) Chasing various potential causes without success.
  ✅ What actually fixed it Performing a 'Crank Relearn' (Crankshaft Position System Variation Learn) procedure finally resolved the misfire code. The procedure was needed because the engine and computer were not original to each other.

"I Checked Everything" — The Actual Cause

• In cases where standard diagnostic procedures like checking for vacuum leaks (with a smoke test), swapping coils, and replacing plugs do not resolve a misfire, the issue may be related to the Crankshaft Position sensor's calibration. A 'Crank Relearn' procedure may be needed to synchronize the sensor with the PCM, a fix that involves no new parts and is purely electronic.

OEM Part Supersession History

• 10457730 → ACDelco D585 / Delphi GN10119 / Standard Motor Products UF262 — Standard part evolution and branding.
  Heads up: Some GM V8s of the era used two distinct ignition coil styles: a square 'Melco' style and a round 'Delphi' style. The LS4 uses the round style, often stamped with the number 19005218. Ensure the replacement coil is the correct round shape.