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2018 RX 350 Rough Idle and Hesitation - Check Engine Light Flashing

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Mike T. · rep 0 · May 24, 2:24 PM · 1 replies · solved · Question

Vehicle: 2018 Lexus RX 350 F Sport

Hey everyone,

I'm experiencing a really frustrating issue with my 2018 Lexus RX 350 F Sport, which has about 75,000 miles on it. Lately, I've noticed a distinct rough idle, especially when I'm stopped at a light. It feels like the engine is shaking more than usual.

On top of that, I've had a few instances where the car seems to hesitate under light acceleration, almost like it's struggling to get power. The most concerning part is that the Check Engine Light started flashing intermittently yesterday, which I know usually means a serious misfire condition.

I've checked the oil, and it seems fine. I'm wondering if this could be spark plugs, ignition coils, or something more serious. Has anyone else with a 2016-2026 RX 350 experienced similar symptoms? Any advice on what I should check before taking it to the dealership?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 24, 2:24 PM

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ClearTheCode admin answer:

Your 2018 Lexus RX 350's symptoms of a rough idle, hesitation, and especially a flashing Check Engine Light (CEL) strongly suggest an active misfire condition. A flashing CEL indicates a severe misfire that could potentially damage the catalytic converter if not addressed promptly.

Common Causes for Misfires in Lexus RX 350 (2016-2026 models):

  1. Ignition System Issues:
    • Worn Spark Plugs: Over time, spark plugs degrade, leading to weak or inconsistent spark. Given your mileage, this is a prime suspect.
    • Faulty Ignition Coils: Each cylinder has its own ignition coil. A failing coil can prevent proper spark to that cylinder.
  2. Fuel System Issues:
    • Clogged Fuel Injectors: Direct injection engines like those in the RX 350 can be prone to carbon buildup on intake valves and potentially clogged fuel injectors, leading to poor fuel atomization.
    • Low Fuel Pressure: A failing fuel pump or clogged fuel filter can reduce fuel delivery.
  3. Air/Vacuum Leaks: Unmetered air entering the engine can disrupt the air-fuel ratio, causing misfires.
  4. Engine Mechanical Problems: (Less common but possible)
    • Low compression in a cylinder due to worn piston rings or valve issues.

Diagnostics:

When the CEL flashes or stays on, the Powertrain Control Module (PCM) stores diagnostic trouble codes (DTCs). You're likely to find codes in the P030x series, where 'x' denotes the specific cylinder misfiring (e.g., P0301 for cylinder 1, P0300 for random/multiple misfires).

What to Do Next:

  1. Minimize Driving: If the CEL is flashing, avoid driving the vehicle extensively to prevent further damage to the catalytic converter.
  2. Retrieve OBD-II Codes: Use an OBD-II scanner to read the stored DTCs. This will pinpoint which cylinder(s) are misfiring and provide crucial clues.
  3. Professional Inspection: Given the flashing CEL, it's highly recommended to have your Lexus inspected by a qualified technician as soon as possible. They can perform a comprehensive diagnosis, including:
    • Reading and interpreting all stored DTCs.
    • Inspecting spark plugs and ignition coils.
    • Checking fuel pressure and injector operation.
    • Performing a compression test if mechanical issues are suspected.

Addressing this issue promptly will prevent more costly repairs down the line.

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