Mitsubishi Repair: 2000 Mitsubishi Eclipse GT, Sportronic, mitsubishi eclipse gt, mitsubishi eclipse

Question
Since it has been getting colder outside it has developed a
couple problems. On a cold start it has a rough idle, and while
the RPM bounces between 200 and 2000 RPM there is also a gas
smell. It feels like a miss in the firing order. Once the car gets
warm, it goes away. No engine lights come on during the erratic
idle.
Another problem is a growl during a cold start. I have had it at
the dealership and the only thing they say is that it "could" be
the flexpipe. As soon as the car gets warm, it goes away.

Any ideas?

Matt

Answer
Matt,
This sounds like an issue with Idle Speed Control (ISC) valve, Fast Idle Air Valve (FIAV), your Exhaust Gas Recirulation (EGR) valve, or a combination of any of those.

The FIAV's purpose is to provide additional air when the engine is cold to increase the idle speed and therefore warm up the engine faster. The FIAV is the reason that coolant flows through the throttle body. The way it works is that the coolant flows around a small wax pellet. As the coolant heats up, the wax pellet melts and the valve closes, thus slowly decreasing the amount of extra air let into your engine.  The ISC's job is to regulate your idle speed, which will be higher when you engine is cold, but the ISC is suppose to prevent the idle from boucing.  A boucing idle is typically called "idle surge".  You should have your ISC checked to make sure it's not damaged.  Your EGR valve allows exhaust gas to recirculate back into your intake to burn off extra fuel.  This is done for emission purposes.  If unregulated exhaust gas is entering your intake, that will cause your cold engine to idle improperly.  

A growl is not uncommon when the engine is cold.  If the sound goes away after the engine warms up, you should not have to worry about the problem.

As for the FIAV, ISC and EGR, the best solution may be to simply clean them.  If you've got a service manual and some idea of how to remove those items, you could do the cleaning yourself with a couple cans of carborator cleaner.  But if you're not comfortable doing it yourself, you can have any mechanic clean it.  Just specify exactly what you want cleaned.  You can instruct your dealership mechanic to do it, but he may charge you more.
Good luck!