4955364 | Genuine Cummins® Exhaust Gas Recirculation Valve ISB 6.7L 2007-2018

• Reduce air pollution

  • It lowers the formation of nitrogen oxides (NOx), which are harmful gases that cause smog.

• Lower combustion temperature

  • By sending some exhaust gas back into the engine, it cools the combustion process.

• Prevent engine knocking

  • Lower temperatures reduce the chance of knocking or pinging.

• Improve engine efficiency (in some conditions)

  • During light driving, it can help the engine run more smoothly and efficiently.

1. EGR Valve Stuck Open

What happens:

• Exhaust gas flows into the engine when it shouldn’t (like at idle).

Symptoms:

• Very rough idle

• Engine stalling at stoplights

• Hard starting

• Engine may feel like it’s “choking”

Why it’s bad:

• The engine needs clean air at idle. Too much exhaust disrupts combustion.

2. EGR Valve Stuck Closed

What happens:

• No exhaust gas is recirculated back into the engine.

Symptoms:

• Engine knocking or pinging

• Higher engine temperatures

• Poor fuel economy

• Failed emissions test

• Check Engine light

Why it’s bad:

• Combustion gets too hot, which increases NOx emissions and engine stress.

3. Carbon Buildup (Most Common Problem)

What happens:

• Carbon deposits clog the valve or EGR passages over time.

Symptoms:

• Hesitation during acceleration

• Rough idle that comes and goes

• Reduced power

• Check Engine light

Why it’s bad:

• The valve may open or close incorrectly, causing inconsistent engine behavior.

4. Electrical or Sensor Failure (Modern Cars)

What happens:

• The EGR valve or its position sensor stops sending correct signals.

Symptoms:

• Check Engine light

• Engine runs okay but fails emissions

• Stored trouble codes (like P0400–P0409)

Why it’s bad:

• The engine computer can’t control emissions properly.

5. Vacuum Line Problems (Older Cars)

What happens:

• Cracked or loose vacuum hoses prevent the EGR valve from operating.

Symptoms:

• Rough idle

• Poor acceleration

• Hissing sound from engine bay