Symptom Chart: Symptom Chart - NVH

Rich fuel conditions Misfire conditions

REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.

Visible rust on surface of exhaust pipes

Catalytic converters/exhaust system

Surface rust is a characteristic of materials used on exhaust systems. Exposure to heat or road salt may result in surface rust. INSPECT for perforations. If there are no perforations, the condition is normal.

Rattle, squeaks or buzz type noise — from the bottom of the vehicle

Loose or damaged heat shield

INSPECT the exhaust system for loose or missing heat shields or foreign material trapped between the heat shields and the exhaust system components. If any heat shields are loose, INSTALL worm gear clamp 7L5Z-5A231-AA and tighten to 7 Nm. If the heat shields are missing or a rattle, noise or buzz condition persists, INSTALL a new heat shield or component as necessary.

Loose or damaged exhaust isolators

VERIFY the exhaust isolators are correctly installed. INSPECT the exhaust isolators for wear or damage. INSTALL new isolators as necessary.

Damaged exhaust isolator hanger bracket

INSPECT the exhaust system components for damage or broken hangers. INSTALL new components as necessary. CHECK for loose or damaged exhaust hanger brackets or fasteners. TIGHTEN the bolts to specification or INSTALL new components as necessary.

Loose or damaged catalytic converters or muffler

MOVE the exhaust system to simulate the bouncing action of the vehicle, checking for exhaust-to-body contact while moving the exhaust system. Using a rubber mallet, TAP on the exhaust components to duplicate the noise concern. Lightly TAP on the muffler, then the catalytic converter. DETERMINE if there are loose or broken baffles in the muffler or a loose or broken element in the catalytic converter. REPAIR or INSTALL new components as necessary.

Exhaust grounded to chassis

INSPECT for signs of exhaust components-to-body contact. REPAIR or INSTALL new components as necessary.

Drone or clunk type noise — from the bottom of the vehicle

Loose or damaged exhaust isolators

INSPECT the exhaust isolators for wear or damage. INSTALL new isolators as necessary.

Exhaust grounded to chassis

INSPECT for signs of exhaust components-to-body contact. REPAIR or INSTALL new components as necessary.

Whistles, boom, hum or ticking type noise — noise tends to change as the engine warms. The noises are often accompanied by exhaust fumes

Exhaust system leak

INSPECT the entire exhaust system for leaks. CHECK for punctures, loose or damaged clamps/fasteners, gaskets, sensors or broken welds. EXAMINE the chassis for grayish-white or black exhaust soot, which indicates exhaust leakage at that point. To magnify a small leak, have an assistant hold a shop towel over the tail pipe outlet while listening for a leak. REPAIR or INSTALL new components as necessary.