Pinpoint Test D: Loss Of Power, Poor Idling, Runs Rough

• Accessory drive concern
• Air intake system concern
• Brake system concern
• Cooling system concern
• Exhaust system concern
• Fuel system concern
• Ignition system concern
• Throttle body concern
• Lubrication system concern
• Turbocharger concern
• Turbocharger bypass valve concern
• Transmission system concern
• Clutch system concern
• Intake or exhaust valve concern
• Valve spring concern
• Valve tappet
• Camshaft
• Cylinder head gasket
• Cylinder head
• Piston or piston ring concern

Visual Inspection and Pre-checks 

• Verify the accessory drive operates correctly.
• Verify the brake system operates correctly.
• Verify the fuel system is free of leaks.
• Verify the throttle body is free of damage.
• Verify the engine oil level is OK.
• Verify the transmission operates correctly.
• Verify the clutch system (if equipped) operates correctly.

• Ignition ON.

• Carry out the PCMKOEO and KOER self-tests.

Are any Diagnostic Trouble Codes (DTCs) present? 

• Check the following Parameter Identifications (PIDs) for simultaneous brake pedal and accelerator pedal operation:
  • Access the PCM and monitor the BRKOVR_ACTION (Undefined / Not Used) PID
  • Access the PCM and monitor the BRKOVRD_POSS (Undefined / Not Used) PID
  • Access the PCM and monitor the DIST_BRKOVRD (km) PID

Is there an indication of both pedals being applied simultaneously? 

• Inspect the air cleaner.

Is the air cleaner clogged? 

• Check the air intake system, air cleaner and CAC components, ducts, pipes and hoses. Check that all components are installed correctly and tight. Check that all components are aligned correctly. Check for damage that could cause an air-intake leak resulting in loss of boost. For additional information, refer to the appropriate Intake Air Distribution and Filtering section for the engine being diagnosed. Refer to the appropriate Engine article(s) for the procedure.

Does the air intake system have any leaks? 

• Check for vacuum leaks.

• If necessary, perform the intake manifold vacuum test. REFER to: Intake Manifold Vacuum Test . Use the intake manifold vacuum test procedure to help identify possible sources of the condition.

Are there any vacuum leaks found? 

• Check for intake manifold vacuum leaks or damage.

Does the intake manifold indicate leaks or damage? 

• Check the exhaust system for restrictions or damage. Refer to the Exhaust System section for the engine being diagnosed. Refer to the appropriate Exhaust System for the procedure.

Is the exhaust system restricted or damaged? 

• Inspect the engine and cooling system for overheating concerns. Refer to the Diagnosis and Testing procedure in the appropriate Engine Cooling article for the engine being diagnosed. Refer to the appropriate Engine article(s) for the procedure.

Is the engine overheating? 

• Inspect the ignition system. Refer to the appropriate Engine Ignition article for the engine being diagnosed. Refer to the appropriate Engine article(s) for the procedure.

Is any concern found with the ignition system? 

• Ignition OFF.

• Remove the spark plugs. Refer to appropriate Engine Ignition article for the engine being diagnosed. Refer to the appropriate Engine article(s) for the procedure. Inspect the spark plugs for signs of inefficient combustion. REFER to: appropriate Spark Plug Inspection . Use the spark plug inspection procedure to help identify possible sources of the condition.

• Perform a compression test and cylinder leakage test. Check the test results for signs of a damaged head gasket cylinder head sealing surfaces or loss of compression or blow by. Check the coolant for bubbles caused by air entering the cooling system from compression. REFER to: Compression and Cylinder Leakage Test .

Does the compression test or cylinder leakage test indicate a loss of compression or excessive cylinder leakage? 

• Inspect the fuel system. Refer to the Diagnosis and Testing procedure in the appropriate Fuel Charging And Controls article for the engine being diagnosed. Refer to the appropriate Engine article(s) for the procedure.

Is the fuel system OK? 

• Check the fuel pressure. Refer to the fuel system pressure check procedure in the appropriate Fuel System for the engine being diagnosed. Refer to the appropriate Fuel System for the procedure. Compare the fuel pressure to the specification listed in the appropriate Fuel System specification procedure.

• Draw a sample of the fuel. Check the fuel for contamination.

Is the fuel pressure within specifications and free of contamination? 

• Check the engine oil pressure. REFER to: Oil Pressure Test  . Compare the engine oil pressure gauge to the engine oil pressure specifications in the specifications procedure of the engine being diagnosed. Refer to the appropriate Engine article(s) for the procedure.

Is the engine oil pressure within specification? 

• Inspect the turbocharger(s) for damage that could cause loss of boost. REFER to the Diagnosis and Testing procedure in the appropriate Fuel Charging and Controls article for the engine being diagnosed. Refer to the appropriate Engine article(s) vvvv for the procedure.

Are the turbocharger(s) damaged? 

• Remove the engine front cover. Inspect the timing components for excessive wear or damage that could cause timing concerns. Check for a stretched timing chain or belt. Check for excessive wear on the timing guides. Check the tensioner plungers for over extension. Inspect the VCT unit(s) for damage or excessive wear.

Is damage found to the timing drive components? 

• Remove the valve cover(s). Visually inspect the camshafts and valve train for obvious signs of excessive wear or damage. Check for broken valve springs, damaged valve retainers, missing or damaged valve keepers or bent valves.

Is damage found to the valve train? 

• Perform the valve train analysis. REFER to: Valve Train Analysis . . Compare the camshaft lift to the specifications for the engine being diagnosed. Refer to the appropriate Engine article(s) for the procedure.

Is the camshaft lift and valve clearance within specifications? 

• Remove the cylinder heads. Refer to the cylinder head procedure(s) for the engine being diagnosed. Refer to the appropriate Engine article(s) for the procedure. Inspect the head gasket(s) for signs of damage or failure. Inspect the cylinder block and cylinder head(s) for damage. REFER to: Cylinder Block Distortion . and REFER to: Cylinder Head Distortion .

Are the cylinder head gasket(s), cylinder head(s) or cylinder block head damaged? 

• Remove the cylinder head(s). Remove the valves from the cylinder heads and inspect the valve stem seals for damage, excessive wear and proper sealing.

Are the valve stem seals damaged? 

• Inspect the valves for excessive engine oil or carbon build up. Inspect the valve seat contact surface and valve seats for damage or wear. Inspect for a burnt or pitted sealing contact surface. Inspect for an even sealing contact surface around the valve and the valve seat. Inspect the valves, valve stems and valve guides for damage. REFER to: Valve Guide Inner Diameter . REFER to: Valve Stem Diameter .

Are the valves damaged or do they show excessive wear or an uneven sealing contact pattern? 

• Disassemble the engine. Check the pistons and piston rings for signs of excessive blow by. Check for excessive carbon build up. Check the pistons, piston rings and cylinder bores for excessive wear or damage. REFER to: Piston Inspection . REFER to: Piston Ring End Gap . REFER to: Cylinder Bore Taper .

Is damage, excessive wear or excessive carbon build up found on the pistons or piston rings?