Symptom Chart - Engine Performance

WARNING: This page is about a different car, the 2008 Mercury Sable, 2008 Ford Taurus X, and 2008 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.

Condition	Possible Sources	Action
Difficult starting	Inoperative or damaged ignition system Air or vacuum leak Inoperative or damaged fuel system Inoperative or damaged starting system	Refer to the appropriate Engine article for the procedure. REFER to the Introduction - Gasoline Engines article.
	Damaged charging system/battery	REFER to CHARGING SYSTEM - GENERAL INFORMATION article.
	Burnt valve	INSTALL a new valve in the cylinder head. TEST the system for normal operation after the repair.
	Worn piston Worn piston rings Worn cylinder	INSTALL a new short block. TEST the system for normal operation after the repair.
	Damaged head gasket	INSTALL a new cylinder head gasket. TEST the system for normal operation after the repair.
	Inoperative or damaged cooling system	REFER to ENGINE COOLING article.
	Fail-safe cooling invoked (if equipped)	REFER to the Introduction - Gasoline Engines article.
Poor idling	Vacuum leaks	Refer to the appropriate Engine article for the procedure. REFER to the Introduction - Gasoline Engines article.
	Inoperative or damaged ignition system	REFER to ENGINE IGNITION - 3.5L article.
	Inoperative or damaged cooling system Inoperative or damaged fuel system	Refer to the appropriate Engine article for the procedure.
	Fail-safe cooling invoked (if equipped)	REFER to the Introduction - Gasoline Engines article.
	Incorrect valve clearance	ADJUST valve clearance. REFER to ENGINE - 3.5L article. TEST the system for normal operation after the repair.
	Incorrect valve-to-valve seat contact	INSTALL a new cylinder head. TEST the system for normal operation after the repair.
	Damaged head gasket	INSTALL a new cylinder head gasket. TEST the system for normal operation after the repair.
Engine runs rough	Inoperative or damaged fuel system Air or vacuum leaks Inoperative or damaged cooling system Inoperative or damaged ignition system	Refer to the appropriate Engine article for the procedure.
	Fail-safe cooling invoked (if equipped)	REFER to the Introduction - Gasoline Engines article.
	Burnt or sticking valve	INSTALL a new valve in the cylinder head. TEST the system for normal operation after the repair.
	Weak or broken valve spring	INSTALL a new valve spring. TEST the system for normal operation after the repair.
	Carbon accumulation in combustion chamber	ELIMINATE carbon buildup. TEST the system for normal operation after the repair.
Excessive oil consumption	Leaking oil	REPAIR oil leakage. TEST the system for normal operation after the repair.
	Inoperative PCV system	REPAIR or INSTALL new components as necessary. TEST the system for normal operation after the repair.
	Incorrect oil	CHANGE oil to correct specification.
	Worn valve stem seal	INSTALL a new valve stem seal. TEST the system for normal operation after the repair.
	Worn valve stem or valve guide	INSTALL a new cylinder head. TEST the system for normal operation after the repair.
	Sticking piston rings Worn piston ring groove Worn piston or cylinder	INSTALL a new short block. TEST the system for normal operation after the repair.
Oil in coolant	Leaking head gasket Leaking oil cooler (if equipped) Damaged cylinder block Damaged cylinder head	INSPECT the engine components. INSTALL new engine components as necessary. Refer to the appropriate Engine article for the procedure. TEST the system for normal operation after the repair.
Coolant in oil	Leaking head gasket Leaking oil cooler (if equipped) Damaged cylinder block Damaged cylinder head Damaged coolant pump/seal/gasket	INSPECT the engine components. INSTALL new engine components as necessary. Refer to the appropriate Engine article for the procedure. TEST the system for normal operation after the repair.
Insufficient power	Inoperative or damaged ignition system Air intake system blockage Lubrication system blockage Inoperative or damaged fuel system	Refer to the appropriate Engine article for the procedure. REFER to the Introduction - Gasoline Engines article.
	Oil level too high	DRAIN oil to correct level. TEST the system for normal operation after the repair.
	Incorrect engine oil	INSTALL correct specification engine oil. TEST the system for normal operation after the repair.
	Excessive accessory drive belt loading Inoperative or damaged cooling system	Refer to the appropriate Engine article for the procedure.
	Fail-safe cooling invoked (if equipped)	REFER to the Introduction - Gasoline Engines article.
	Damaged or plugged exhaust system	INSPECT exhaust system.
	Incorrect tire size	REFER to SUSPENSION SYSTEM - GENERAL INFORMATION article.
	Dragging brakes	REFER to BRAKE SYSTEM - GENERAL INFORMATION article.
	Slipping transmission	REFER to AUTOMATIC TRANSAXLE/TRANSMISSION - 6F50 article.
	Incorrect valve clearance	ADJUST valve clearance. REFER to ENGINE - 3.5L article. TEST the system for normal operation after the repair.
	Worn or damaged valve tappet	INSTALL a new valve tappet. TEST the system for normal operation after the repair.
	Damaged valve guide Compression leakage at valve seat Seized valve stem	INSTALL a new cylinder head assembly. TEST the system for normal operation after the repair.
	Weak or broken valve spring	INSTALL a new valve spring. TEST the system for normal operation after the repair.
	Worn or damaged cam	INSTALL a new camshaft. TEST the system for normal operation after the repair.
	Damaged head gasket	INSTALL a new head gasket. TEST the system for normal operation after the repair.
	Cracked or distorted cylinder head	INSTALL a new cylinder head assembly. TEST the system for normal operation after the repair.
	Damaged, worn or sticking piston ring(s) Worn or damaged piston	INSTALL a new short block. TEST the system for normal operation after the repair.