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2021 Terrain 1.5T Excessive Oil Consumption & Turbo Lag

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Kim L. · rep 0 · May 22, 3:38 AM · 1 replies · solved · Question

Vehicle: 2021 GMC Terrain SLT

I'm reaching out because I've noticed a couple of concerning issues with my 2021 GMC Terrain SLT, which has the 1.5L turbocharged engine. First, it seems to be consuming oil at an alarming rate. I find myself adding a quart every 2,000-3,000 miles, which feels excessive for a vehicle with only 45,000 miles on it.

Secondly, I've started to experience noticeable turbo lag and a general sluggishness in acceleration. It just doesn't feel as responsive as it used to. I haven't had a consistent Check Engine Light, but I did get a P0299 (Turbocharger Underboost) once, which cleared itself. I'm worried these issues might be related. Has anyone else with the 1.5T engine in their Terrain or Equinox experienced similar problems?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:38 AM

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ClearTheCode admin answer:

Excessive oil consumption and turbo lag on the 1.5L turbocharged engine (LYX) in the 2021 GMC Terrain are issues that have been reported by some owners. These two symptoms can indeed be related.

Common Causes for Oil Consumption:

  1. PCV System Issues: A clogged or malfunctioning Positive Crankcase Ventilation (PCV) system can lead to increased crankcase pressure, forcing oil past seals and into the intake or combustion chamber. This is a common culprit for oil consumption in many modern engines.
  2. Turbocharger Seals: The turbocharger operates at high speeds and temperatures. Worn or failing seals within the turbo can allow oil to leak into the intake or exhaust side, leading to consumption and potentially smoke from the exhaust.
  3. Piston Ring Issues: While less common on newer vehicles, issues with piston rings can lead to oil bypassing into the combustion chamber.

Common Causes for Turbo Lag/Underboost (P0299):

  1. Wastegate Actuator/Solenoid: The wastegate controls exhaust gas flow to the turbo. If its actuator or control solenoid is faulty, it can prevent the turbo from building boost effectively.
  2. Boost Leaks: Leaks in the intercooler, charge pipes, or vacuum lines can cause a loss of boost pressure, leading to underboost and sluggish performance.
  3. Turbocharger Failure: In some cases, the turbocharger itself may be failing, either due to internal wear or damage.
  4. Clogged Catalytic Converter: A severely restricted exhaust can prevent the turbo from spooling up correctly.

What to do:

  1. PCV System Inspection: Have a mechanic inspect the PCV valve and associated hoses for clogs or damage.
  2. Boost Leak Test: A shop can perform a boost leak test to check for leaks in the turbo system.
  3. Turbocharger Inspection: The turbocharger should be inspected for shaft play, oil leaks, and proper wastegate operation.
  4. Oil Consumption Test: A dealership or shop can perform a controlled oil consumption test to accurately measure the rate of consumption and help diagnose the root cause.

When to see a shop:

Both excessive oil consumption and turbocharger issues can lead to significant engine damage if left unaddressed. Excessive oil burning can foul spark plugs, damage catalytic converters, and lead to carbon buildup. Turbo lag and underboost indicate a problem that could worsen, potentially leading to complete turbo failure. It's highly recommended to have your Terrain professionally diagnosed as soon as possible.

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