The exhaust gas recirculation valve (EGR) on a 1991 Nissan Altima is a very important part of the exhaust gas system, so how does it work? As the name suggests, it takes a portion of the exhaust gas and recirculates it back into the engine (the combustion chamber). The idea is to make the engine run more efficiently as well as decreasing the pollution emitted from the exhaust.
- By reintroducing exhaust gases into the combustion chamber it helps the reduction of nitrogen oxides being formed. This helps the pollutants emitted being at a more acceptable level per vehicle. The EGR valve on a 1997 Nissan Altima is usually a golden colored item, which is located high up on the firewall inside the engine bay. It has one vacuum line running from it and is attached to the firewall by two bolts.
- Most EGR valves are mechanical, and allow a small portion of exhaust gas to recirculate. Most of the gas is pumped out of the exhaust system. Once there is sufficient back pressure in the exhaust chamber, the EGR valve opens, which keeps the air/fuel mixture running at an optimal range. Depending on what revs are being used, an air/fuel ratio of 14:1 is perfect.
- Over the years of opening and closing, a common fault with the EGR valve on a 1997 Nissan Altima is it getting stuck open or closed. If it is stuck open, this causes a vacuum leak and can cause the engine to idle badly and stutter when accelerating. Cleaning the valve with carb cleaner or a wire brush is helpful but check the valve first to see if the plunger shaft moves when the engine is revved.
- If the valve is stuck in the closed position, the vehicle will produce higher nitrogen oxide emissions than normal and there may be a knocking noise from the air/fuel mixture igniting before it reaches the combustion chamber.