an EGR valve that's stuck open will cause a noticeable drop in horsepower at the very least. Along with that may come detonation -- "knock" or "ping" -- under hard acceleration, and the attendant cylinder misfires. The engine will also see an open EGR valve as a massive vacuum leak, so expect hard starting and a very rough idle. An EGR stuck closed or clogged with carbon won't exhibit many symptoms, since engines don't technically need them to run. But expect a very noticeable drop in fuel economy, a noticeable gasoline smell from the exhaust pipe, a very hot catalytic converter, or all of the above.

 

thank you so much. got all of those symptoms( besides hot cat...aint got none..lol) but this was a ton of help. I just picked a new egr up today

 

You can use a scan tool to check actual operation of the EGR valve. If the scan tool detects an error code, then it’s likely that the sensor has gone bad and will need to be replaced.

Also inspect the tubing that runs from the exhaust manifold to the EGR as sometimes this can get clogged, restricting flow, which will cause drivability issues. You’ll be able to identify this by running the engine and then disconnecting the tube from the EGR. If you can’t feel any vacuum pressure and the engine idle doesn’t change, there’s a clog somewhere in the system, as normally a leak in the EGR system, with exhaust gas still recirculating, will cause the engine to run rough. However, in most cases the EGR rarely fails, and there may be a problem elsewhere.