The 1990 Ford Mustang GT was equipped with a 5.0-liter eight-cylinder engine. It came with several different standard features, including a driver front airbag, bucket seats, power brakes, tilt steering wheel, 15-inch wheels, alloy wheels, power windows and power exterior mirrors. Because the Mustang is made up of many different systems, parts and components, it can be difficult to troubleshoot what parts need to be replaced when you are having a problem with your vehicle. One method is to notice different type and location of smells your Mustang emits as you use the car.
Locate the oxygen sensor when the Mustang has a sulfur or rotten egg smell coming out of the exhaust system. The sensor may be damaged or faulty. You should also check the PCV valve and catalytic converter to see if they are clogged or faulty. Find the carburetor to see if it is dirty or broken and check the PCV hose to see if it is clogged or is collapsed.2
Look at the Mustang's valve stem seals when the car emits a smoke smell out of the exhaust when you start up the car. The seals may be damaged or faulty. Inspect the head gasket inside the engine to determine whether there is any coolant leaking into the engine's cylinders.3
Inspect the oil filler cap when you smell oil around the engine compartment while the Mustang is parked. The cap may be damaged or missing. You should also inspect the PCV valve, the valve grommet and valve elbow to determine whether any of these components are plugged, damaged or collapsed. Look also at the head gasket to see if oil is leaking out of it because the gasket is damaged or faulty.4
Find and examine the Mustang's heater core when you smell a mold or mildew odor inside the passenger compartment. The heater core may be leaking coolant into the Mustang's floor area. If the moldy smell is coming from the trunk check the weather stripping around the trunk door to see if it is stripped or worn and is allowing water to enter the trunk.