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Rough Idle & Check Engine Light - 2017 Chevy Malibu 1.5T

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Mike T. · rep 0 · May 25, 1:42 AM · 1 replies · solved · Question

Vehicle: 2017 Chevrolet Malibu LT

My 2017 Chevrolet Malibu LT with the 1.5L turbo engine recently started running really rough, especially at idle. It feels like it's misfiring, and the Check Engine Light came on. I took it to AutoZone and they pulled a P0302 code, which indicates a misfire on cylinder 2.

I'm thinking it could be spark plugs or an ignition coil. Is this a common problem for the 1.5T engine in these Malibus? What's the best way to diagnose if it's the plug or the coil, and how difficult is it to replace them myself?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 1:42 AM

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ClearTheCode admin answer:

The P0302 code on your 2017 Chevrolet Malibu LT (1.5L turbo) indicating a misfire on cylinder 2 is a common issue that can often be traced back to either a faulty spark plug or a failing ignition coil. The 1.5T engine, like many direct-injection engines, can be a bit sensitive to spark plug condition.

DIY Diagnosis & Replacement Steps:

  1. Confirm Cylinder 2: Locate cylinder 2. On most inline 4-cylinder engines, cylinder 1 is at the front of the engine (timing belt/chain side), so cylinder 2 would be the second one from the front.
  2. Coil Swap Test (Diagnosis):
    • Engine Off & Cool: Ensure the engine is off and cool.
    • Locate Coils: The ignition coils are typically located directly on top of each spark plug.
    • Swap: Disconnect the electrical connector and remove the ignition coil from cylinder 2. Swap it with an adjacent cylinder's coil (e.g., cylinder 1 or 3).
    • Clear Codes & Test Drive: Clear the P0302 code using an OBD-II scanner. Drive the car. If the misfire now moves to the cylinder you swapped the coil to (e.g., if you swapped with cylinder 1 and now get a P0301 code), then the ignition coil is faulty and needs replacement.
  3. Spark Plug Replacement (If Coil is Good):
    • If the coil swap doesn't move the misfire, the spark plug in cylinder 2 is the next suspect.
    • Tools: You'll need a spark plug socket (typically 5/8" or 16mm), an extension, and a ratchet. A torque wrench is highly recommended for proper installation.
    • Remove Plug: Remove the coil from cylinder 2. Use the spark plug socket to carefully remove the spark plug.
    • Inspect: Examine the old plug for signs of wear, fouling, or damage.
    • Install New Plug: Install a new, correctly gapped spark plug (always use the OEM-specified plug type for your 1.5T engine, usually iridium) and torque it to the manufacturer's specifications. Reinstall the coil and connector.

Causes of Misfires & When to See a Shop:

  • Worn Spark Plugs: Over time, the electrodes wear down, leading to a weaker spark.
  • Failing Ignition Coils: Coils can fail due to age, heat, or manufacturing defects, preventing a strong spark.
  • Fuel Injector Issues: A clogged or failing fuel injector can also cause a misfire by not delivering enough fuel to the cylinder.
  • Compression Issues: Less common but more serious, low compression in a cylinder can cause misfires.

If replacing the spark plug and coil doesn't resolve the P0302 code, or if you encounter new codes like P0202 (fuel injector circuit malfunction) or P0420 (catalyst efficiency), it's time to take your Malibu to a qualified mechanic. They have advanced diagnostic tools to test fuel injectors, check compression, and identify more complex engine issues.

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