from http://autorepair.about.com/library/.../bldef-176.htmhttp://autorepair.about.com/library/.../bldef-176.htm
EXHAUST GAS RECIRCULATION
This is an emissions control technique for reducing oxides of nitrogen emissions in the tailpipe. A small amount of exhaust gas is recirculated back into the intake manifold to dilute the incoming air/fuel mixture. Contrary to what you'd think, it has a cooling effect on combustion temperatures that helps reduce the formation of oxides of nitrogen (See NoX). The EGR valve is the main control device in this system.
The EGR valve is the main emissions control component in the exhaust gas recirculation system. The valve is located on the intake manifold, and opens a small passageway between the exhaust and intake manifold to allow a metered amount of exhaust to flow back into the engine. This reduces combustion temperatures and helps control the formation of oxides of nitrogen. The EGR valve is opened by the application of vacuum to its control diaphragm. Some also require a certain amount of exhaust back pressure before they'll open. On newer vehicles, the valve is electronic and uses one or more solenoids or a small stepper motor. The valve should remain closed while the engine is cold and at idle. It should only open once the engine has warmed up and is running at part-throttle. If the valve sticks shut (or is disconnected), NOX emissions will soar and detonation will often result (See Detonation and Spark Knock). If it sticks in the open position or fails to close all the way, it acts like a vacuum leak resulting in a rough idle, hesitation and possible stalling.
__________________
rodski afaik did a diy cleaning of his carnival's egr valve which he detailed in some posts early in this thread. the eqr cleaning can also be done in any kia casa or reputable repair shop. afaik it is a half-day job. the turbo cleaning can be done in one day and one can elect to have the egr serviced at the same time. the only problem with having them done at the same time is that one will not be able to see which service has done the better improvement to performance. if one has the time, i think it is better to have one service done after the other.
following mikey177's advice i searched the tsikot threads re turbo cleaning. this one came up. interesting. anyway, this is the key post
Originally Posted by v22






![Google Play The Kia Sedona/Carnival Thread [ARCHIVE]](https://play.google.com/intl/en_us/badges/images/generic/en_badge_web_generic.png)