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2023 CT4-V Blackwing Cold Start Stumble & Rich Smell

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Mike T. · rep 0 · May 25, 2:50 AM · 1 replies · solved · Question

Vehicle: 2023 Cadillac CT4-V Blackwing

I've got a 2023 Cadillac CT4-V Blackwing with the 3.6L Twin-Turbo, and lately, I've noticed a peculiar issue during cold starts. The engine sometimes stumbles quite a bit, almost like it's struggling to catch, and occasionally takes a second or two longer to fire up than usual.

Once it starts, there's often a strong smell of fuel, almost like it's running rich, for the first minute or so. After that, it smooths out and drives perfectly fine with no noticeable performance issues or Check Engine Light.

This only happens on a cold start, after the car has been sitting for several hours. Has anyone else with a CT4-V Blackwing or similar twin-turbo V6 experienced this? Could it be related to fuel delivery, like injectors or the fuel pump? Any insights would be great.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:50 AM

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ClearTheCode admin answer:

The cold start stumble and rich fuel smell on your 2023 Cadillac CT4-V Blackwing, especially with no CEL, points towards a nuanced fuel delivery or ignition issue that's more pronounced when the engine is cold and fuel systems are under different pressure/temperature conditions. Here's what to consider:

  1. Potential Causes:

    • High-Pressure Fuel Pump (HPFP) / Low-Pressure Fuel Pump (LPFP): These engines use both a low-pressure in-tank pump and a high-pressure direct injection pump. Issues with either, especially the HPFP, can cause incorrect fuel pressure during cold starts. If the HPFP isn't building pressure correctly, the engine might struggle.
    • Fuel Injectors: Leaky or partially clogged fuel injectors can cause an overly rich condition on startup, leading to stumbling and a fuel smell. If an injector is dribbling fuel into a cylinder when the engine is off, it can cause a rough start as that cylinder tries to fire with too much fuel.
    • Fuel Pressure Sensor: A faulty fuel pressure sensor might be providing incorrect readings to the engine control module (ECM), leading to an incorrect fuel mixture during startup.
    • Spark Plugs/Ignition Coils: While less likely if it's strictly a cold start issue and no CEL, slightly weak spark on a cold, rich mixture could contribute to the stumble.
    • Engine Coolant Temperature (ECT) Sensor: An inaccurate ECT sensor could tell the ECM the engine is colder or warmer than it actually is, leading to incorrect fuel enrichment for starting.

  2. Diagnostics:

    • Fuel Pressure Test: A shop can monitor both low and high-side fuel pressure during cold start and operation to identify any anomalies.
    • Injector Leak Test: Specialized equipment can test for leaky injectors.
    • OBD-II Codes: Even without a CEL, pending or historical codes might exist. Look for codes like:
      • P0172/P0175: System Too Rich (Bank 1/Bank 2) – Could be triggered if the rich condition is severe enough.
      • P0087: Fuel Rail/System Pressure - Too Low – If the HPFP isn't performing adequately.
      • P0088: Fuel Rail/System Pressure - Too High – Less likely, but possible with a faulty regulator.

  3. When to See a Shop:

    • Soon: While it's not throwing a CEL yet, persistent rich conditions or fuel system issues can eventually damage catalytic converters or lead to driveability problems. Given this is a high-performance engine, it's best to have a Cadillac dealer or a performance shop with experience in these engines diagnose it. They have the specific diagnostic tools and knowledge to pinpoint the exact component causing the issue.
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