my GMC Sierra T1XX (2019-Present) is running rough and losing power, what should I check?

Learn how to diagnose and fix engine running rough and losing power in GMC Sierra T1XX. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Tools Required: OBD-II scanner, basic hand tools (sockets and wrenches), fuel pressure gauge, vacuum gauge, spark plug socket.
• Disconnect the battery before starting any work, to ensure safety while handling electrical components.

2. Address Fuel System Issues

1. Check Fuel Pressure:

   • Connect the fuel pressure gauge to the fuel rail.
   • Turn the ignition key to the "ON" position (without starting the engine) to prime the system.
   • Verify that the pressure meets factory specifications (typically around 55-62 psi).
   • If pressure is low, inspect the fuel pump and filter for blockages or failures.

2. Replace Fuel Filter (if necessary):

   • Locate the fuel filter (usually on the frame rail or in-line with the fuel line).
   • Use appropriate wrenches to disconnect the fuel lines.
   • Remove the old filter and install the new one, ensuring correct orientation.
   • Reconnect the fuel lines and check for leaks.

3. Inspect and Replace Spark Plugs

1. Remove Spark Plugs:

   • Locate the spark plugs (typically under the engine cover).
   • Use a spark plug socket to carefully remove each plug, inspecting for wear or fouling.

2. Install New Spark Plugs:

   • Gap the new spark plugs according to manufacturer specifications.
   • Install the new plugs by hand, then tighten to the specified torque (usually around 11-15 lb-ft).
   • Reconnect ignition coil connectors.

4. Check and Replace Ignition Coils (if needed)

1. Inspect Ignition Coils:

   • Remove the ignition coils from the spark plugs.
   • Look for cracks or damage on the coil housing.

2. Replace Faulty Coils:

   • If any coils are damaged, replace them with new units.
   • Reattach the coils and ensure connectors are secure.

5. Test for Vacuum Leaks

1. Perform a Vacuum Leak Test:
   • Use a vacuum gauge to check engine vacuum at idle.
   • If low, inspect all vacuum hoses and the intake manifold for leaks.
   • Replace or repair any damaged hoses.