Mitsubishi Repair: damn diamante, coolant levels, exhaust gas recirculation

Question
I have this 1995 mitsu diamante 3.0 dohc ...its ran fine for almost 3 yrs...onw night I rinsed off under the hood with a light water spray the next day I noticed the car was hesitating..when I take my foot off the gas pedal the rpms will decrease down a bit then good back up at mid to high rpms it seems fine though the  acceleration is lil something to be desired to  ...most noticeable when Im at a stop the rpms will go from 750(normal idle) down to 500 and then back up.....I assumed it needs a tune up..what else can be causing the problem?

PS also arift of white smoke out he tail pipe only after I pull off from idle and a complete stop it soon disipatates...what the hell?

Answer
Uni,
I'm not sure if washing your car had anything to do with your problem, but sometimes excess water can cause minor hesitation problems.  But i think your occurance is just a coinsidence.

A tune-up will most likely fix you problem.  Have your mechanic replace your air filter, fuel filter, and PCV valve.  Your spark plugs and plug wires should also be replaced.  Also have your mechanic check and clean your Exhaust Gas Recirculation (EGR) valve, Idle Air Controller (IAC), and throttle body.  A surging idle is typically caused by an erratic amount of air entering your engine.  Having those items checked out will most likely reveal your problem.

If you see white smoke coming from your exhaust even after your engine has warmed up, that could indicate oil leaking past your valve seals and burning up in your combustion chamber.  It may also be a sign of coolant leaking past your head gasket and burning off in your exhaust.  Either problem would require some pretty expensive labor.  But if it's minor and only happens when your engine is cold, it'll probably be fine for now.  Just keep an eye on your oil and coolant levels.
Good luck!