For 1990-2009 cars

Symptom | Cause
--- | ---
There are four steps to diagnosing engine noise. You must determine the following:

• | The type of noise

| For example, is the noise a light rattle/tapping or a low rumble/knocking?

• | The exact operating condition under which the noise exists

| Note factors such as the ambient temperature, the amount of engine warm-up time, the engine temperature, engine RPM's, and other specifics.

• | At what rate the noise occurs, and at what location in the engine

| Remember, engine noises are generally synchronized to either engine speed (crankshaft, flywheel, connecting rods, balancer, or pistons and related components) or one-half engine speed (valve train noise such as valve lifters and the timing belt). Try to determine the rate at which the noise is occurring.

• | Compare the engine sounds to other engines and make sure you are not trying to correct a normal condition.

Noise on Start-Up but Only Lasts a Few Seconds |

• | Improper oil viscosity. Install the recommended oil viscosity for the expected temperatures.

• | Worn or dirty valve lifters

• | Excessive piston to bore clearance

• | Excessive piston pin to piston clearance

• | Excessive crankshaft bearing clearance

Knocks Cold and Continues for 1 to 2 Minutes |

• | Loose or broken crankshaft balancer or accessory drive components

• | Excessive piston to bore clearance

| A cold piston knock which disappears in 1.5 minutes should be considered acceptable.

Intermittent Noise on Idle, Disappearing When Engine Speed is Increased |

• | Improper oil viscosity. Install the recommended oil viscosity for the expected temperatures.

• | Low oil pressure

| Install an oil pressure gauge and measure the engine oil pressure.

• | Dirty or worn valve lifter

Valve Train Noise (Rattle/Tapping) | The following conditions may cause valve train noise:

• | Low oil pressure

• | Worn or faulty oil pump

• | Broken valve spring

• | Sticking valves

• | Worn, dirty, or faulty valve lifters

• | Worn camshaft lifter lobes

• | Worn valve guides or valve stems

• | Bent, broken, or damaged timing belt sprocket teeth

Knocks at Idle Hot (Rumble/Knocking) | The following conditions may cause a knocking noise:

• | Malfunctioning accessory drive system components

• | Detonation or spark knock

| Check for proper operation of the cooling, knock, and ignition control components.

• | Excessive connecting rod bearing clearance

• | Excessive piston pin to bore clearance

• | Bent connecting rod

• | Excessive crankshaft main or thrust bearing clearance

• | Loose torque converter bolts

• | Cracked or damaged flywheel

• | Exhaust leak at the manifold

Exhaust System Noise and/or Leakage | Exhaust system noise and/or leakage may be caused by the following conditions:

• | Improperly installed or misaligned exhaust system components

• | A cracked or broken exhaust manifold

• | Damaged or worn gaskets and/or seals

• | Burned or rusted out exhaust system components

• | A broken or loose exhaust clamp and/or bracket