Where is the egr valve located on a 1999 Chevy suburban and what are typical symptoms of an failure?

The EGR valve location on a 1999 Chevy Suburban varies slightly depending on the engine (5.7L, or 7.4L). However, it's generally found on the intake manifold, near the back of the engine. It's usually a small, rectangular or cylindrical component with a vacuum line connected to it. You'll likely need to consult a repair manual specific to your Suburban's engine for the precise location as it can be difficult to visually identify without prior knowledge. A diagram showing its location would be highly beneficial.

Typical symptoms of a failing EGR valve include:

* Rough idle: The engine may idle roughly, especially when warm.

* Poor fuel economy: The engine's efficiency decreases, leading to lower gas mileage.

* Hesitation or stalling: The engine may hesitate during acceleration or even stall.

* Check engine light: This is a very common symptom, usually accompanied by a diagnostic trouble code (DTC) related to the EGR system. You'll need an OBD-II scanner to read the code.

* Excessive emissions: The vehicle will produce more pollutants than normal.

* Lack of power: The engine may feel sluggish or lack power.

* Knocking or pinging: A malfunctioning EGR valve can sometimes contribute to engine knocking or pinging, especially under load.

Important Note: A stuck-open EGR valve is generally worse than a stuck-closed one. A stuck-open valve can lead to serious engine damage because it allows excessive exhaust gases to enter the combustion chambers which significantly reduces engine performance and can potentially melt pistons.

Before you attempt any repairs, it's recommended to have a mechanic diagnose the problem to confirm it is indeed the EGR valve, and avoid more complex issues. A simple visual inspection may not always be sufficient; a proper diagnostic scan is needed.