Engine Troubleshooting - rough idle, hesitation, backfire, detonation, low oil pressure and more

General Automotive Repair

The general trouble shooting information lists common vehicle symptons with possible solutions and is not for any particular vehicle make and model. For repair info specifically for your make and model please view the main directory.

Engine Lopes At Idle

• Intake manifold-to-head leaks: Replace manifold gasket
• Blown head gasket: Replace head gasket
• Worn timing gears, chain or sprocket: Replace gears, chain or sprocket
• Worn camshaft lobes: Replace camshaft
• Overheated engine: Check cooling system
• Blocked crankcase vent valve: Remove restriction
• Leaking EGR valve: Repair leak and or replace valve
• Faulty fuel pump: Replace fuel pump

Engine Has Low Power

• Leaking fuel pump: Repair leak and/or replace fuel pump
• Excessive piston-to-bore clearance: Install larger pistons
• Sticking valves or weak valve springs: Check valve train components
• Incorrect valve timing: Reset valve timing
• Worn camshaft lobes: Replace camshaft
• Blown head gasket: Replace head gasket.
• Clutch slipping: Adjust pedal and or replace components
• Engine overheating: Check cooling system
• Auto. Trans. pressure regulator valve faulty: Replace pressure regulator valve
• Auto. Trans. fluid level too low: Add fluid as necessary
• Improper vacuum diverter valve operation: Replace vacuum diverter valve
• Vacuum leaks: Inspect vacuum system and repair as required
• Leaking piston rings: Replace piston rings

Car hesitates at high speed

• Low fuel pump volume: Replace fuel pump
• Leaking valves or worn: Replace valves and/or springs
• Incorrect valve timing: Reset valve timing
• Intake manifold restricted: Remove restriction
• Worn distributor shaft: Replace distributor

Slow Acceleration

• Improper fuel pump stroke: Remove pump and reset pump stroke
• Incorrect ignition timing: Reset ignition timing
• Leaking valves: Replace valves
• Worn fuel pump diaphragm or piston: Replace diaphragm or piston

Intake Backfire

• Improper ignition timing: Reset ignition timing
• Faulty accelerator pump discharge: Replace accelerator pump
• Improper choke operation: Check choke and adjust as required
• Defective EGR valve: Replace EGR valve
• Fuel mixture too lean: Reset air and fuel mixture
• Choke valve initial clearance too large: Reset choke valve initial clearance

Exhaust Backfire

• Vacuum leak: Inspect and repair vacuum system
• Faulty vacuum diverter valve: Replace vacuum diverter valve
• Faulty choke operation: Check choke and adjust as required
• Exhaust system leak: repair exhaust system leak

Detonation or pinging noise from engine

• Ignition timing too far advanced: Reset ignition timing
• Faulty ignition system: Check ignition timing
• Spark plugs loose or faulty: Retighten or replace plugs
• Fuel delivery system clogged: Inspect lines, pump and filter for clog
• EGR valve inoperative: Replace EGR valve
• PCV system inoperative: Inspect and/or replace hoses or valve
• Vacuum leaks: Check vacuum system and repair leaks
• Excessive combustion chamber deposits: Remove built-up deposits
• Leaking, sticking or broken valves: Inspect and/or replace valves

Oil leaking from the outside of engine

• Fuel pump improperly seated or worn gasket: Remove pump, replace gasket and seat properly
• Oil pan gasket broken or pan bent: Straighten pan and replace gasket
• Timing chain cover gasket broken: Replace timing chain cover gasket
• Rear main oil seal worn: Replace rear main oil seal
• Oil pan drain plug not seated properly: Remove and reinstall drain plug
• Camshaft bearing drain hole blocked: Remove restriction
• Oil pressure sending switch leaking: Remove and reinstall sending switch

Excessive Oil Consumption

• Worn valve stems or guides: Replace stems or guides
• Valve "O" ring seals damaged: Replace "O" ring seals
• Plugged oil drain back holes: Remove restrictions
• Improper PCV valve operation: Replace PCV valve
• Engine oil level too high: Remove excess oil
• Engine oil too thin: Replace thicker oil
• Valve stem oil deflectors damaged: Replace oil deflectors
• Incorrect piston rings: Replace piston rings
• Piston ring gaps not staggered: Reinstall piston rings
• Insufficient piston ring tension: Replace rings
• Piston ring grooves or oil return slots clogged: Replace piston rings
• Piston rings sticking in grooves: Replace piston ring
• Piston ring grooves excessively worn: Replace piston and rings
• Compression rings installed upside down: Replace compression rings correctly,
• Worn or scored cylinder walls: Rebore cylinders or replace block
• Mismatched oil ring expander and rail: Replace oil ring expander and rail
• Intake gasket dowels too long: Replace intake gasket dowels
• Excessive main or connecting rod bearing clearance: Replace main or connecting rod bearings

No Oil Pressure

• Low oil level: Add oil to proper level
• Oil pressure sender or gauge broken: Replace sender or gauge
• Oil pump malfunction: Remove and overhaul oil pump
• Oil pressure relief valve sticking: Remove and reinstall valve
• Oil pump passages blocked: Overhaul oil pump
• Oil pickup screen or tube blocked: Remove restriction
• Loose oil inlet tube: Tighten oil inlet tube
• Loose camshaft bearings: Replace camshaft bearings
• Internal leakage at oil passages: Replace block or cylinder head

Low Oil Pressure

• Low engine oil level: Add oil to proper level
• Engine oil too thin: Remove and replace with thicker oil
• Excessive oil pump clearance: Reduce oil pump clearance
• Oil pickup tube or screen blocked: Remove restrictions
• Main, rod or cam bearing clearance excessive: Replace bearing to reduce clearance

High Oil Pressure

• Improper grade of oil: Replace with proper oil
• Oil pressure relief valve stuck closed: Eliminate binding
• Oil pressure sender or gauge faulty: Replace sender or gauge

Noisy Main Bearings

• Inadequate oil supply: Check oil delivery to main bearings
• Excessive main bearing clearance: Replace main bearings
• Excessive crankshaft end play: Replace crankshaft
• Loose flywheel or torque converter: Tighten attaching bolts
• Loose or damaged vibration damper: Tighten or replace vibration damper
• Crankshaft journals out-of-round: Re-grind crankshaft journals
• Excessive belt tension: Loosen belt tension

Noisy Connecting Rods

• Excessive bearing clearance or missingbearing: Replace bearing
• Crankshaft Crankshaft]] rod journal out-of-round: Re-grind crankshaft journal
• Misaligned connecting rod or cap: Remove rod or cap and realign
• Incorrectly tightened rod bolts: Remove and re-tighten rod bolts

Noisy Pistons and Rings

• Excessive piston-to-bore clearance: Install larger pistons
• Bore tapered or out-of-round: Rebore block
• Piston ring broken: Replace piston rings
• Piston pin loose or seized: Replace piston pin
• Connecting rods misaligned: Realign connecting rods
• Ring side clearance too loose or tight: Replace with larger or smaller rings
• Carbon build-up on piston: Remove carbon build up

Noisy Valve Train

• Worn or bent push rods: Replace push rods
• Worn rocker arms or bridged pivots: Replace push rods
• Dirt or chips in valve lifters: Remove lifters and remove dirt/chips
• Excessive valve lifter leak-down: Replace valve lifters
• Valve lifter face worn: Replace valve lifters
• Broken or cocked valve springs: Replace or reposition springs
• Too much valve stem-to-guide clearance: Replace valve guides
• Valve bent: Replace valve
• Loose rocker arms: Retighten rocker arms,
• Excessive valve seat run-out: Reface valve seats
• Missing valve lock: Install new valve lock
• Excessively worn camshaft lobes: Replace camshaft
• Plugged valve lifter oil holes: Eliminate restriction or replace lifter
• Faulty valve lifter check ball: Replace lifter check ball
• Rocker arm nut installed upside down: Remove and reinstall correctly
• Valve lifter incorrect for engine: Remove and replace valve lifters
• Faulty push rod seat or lifter plunger: Replace plunger or push rod

Noisy Valves

• Improper valve lash: Re-adjust valve lash
• Worn or dirty valve lifters: Clean and/or replace lifters
• Worn valve guides: Replace valve guides
• Excessive valve seat or face run-out: Reface seats or valve face
• Worn camshaft lobes: Replace camshaft
• Loose rocker arm studs: Re-tighten rocker arm studs
• Bent push rods: Replace push rods
• Broken valve springs: Replace valve springs

Burned, Sticking or Broken Valves

• Weak valve springs or warped valves: Replace valves and/or springs
• Improper lifter clearance: Re-adjust clearance or replace lifters
• Worn guides or improper guide clearance: Replace valve guides
• Out-of-round valve seats or improper seatwidth: Re-grind valve seats
• Gum deposits on valve stems, seats or guide: Remove deposits
• Improper spark timing: Re-adjust spark timing

Broken Pistons and Rings

• Undersize pistons: Replace with larger pistons
• Wrong piston rings: Replace with correct rings,
• Out-of-round cylinder bore: Re-bore cylinder bore
• Improper connecting rod alignment: Remove and realign connecting rods
• Excessively worn ring grooves: Replace pistons,
• Improperly assembled piston pins: Re-assemble pin-to-piston
• Insufficient ring gap clearance: Install new rings
• Engine overheating: Check cooling system
• Incorrect ignition timing: Re-adjust ignition timing
• Leaks at manifold to head, or to pipe: Replace manifold or pipe gasket
• Exhaust manifold cracked or broken: Replace exhaust manifold

General Automotive Repair

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