Start by cleaning the throttle body and around the throttle plate but it sounds like a vacuum leak, 200,000 miles is a lot. Get your hands on a scan tool that displays data and look at the IAC counts when it is idling normally all warmed up. If the counts are zero or close to it the computer is trying to bring the idle down because the engine is idling off of unauthorized air (a vacuum leak).
Fuel filter.
It sounds also like the cold start idle mechanism is out of adjustment. On an older car this would be the choke. On a newer one with fuel injection, the idle is supposed to be set a little higher at a cold start until the fuel vapor is normalized and the engine is warm.
FUEL PRESSURE REGULATOR,, GET THE KIT ,, BORG WARNER MAKES ONE THAT TAKES LESS THAN 15 MINUITS TO REPLACE GO TO ANY GOOD AUTO PARTS DEALER>>> IVE RUN INTO THIS PROBLEM ON LOTS OF GM ENGINES .....
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My 1999 Chevy Malibu with the 3100 V6 has a "hot soak" restart problem. When ever I drive it for a good long drive and then park it, and restart it within 20 minutes, it starts fine. But if I leave it for more than that, and start it, it starts then stalls. Then it keeps stalling unless I rev the engine a bit. Then the idle will surge up and down between nearly stalling and 1200 RPM. Then it will stall out again. I have to keep my foot on the gas until it runs for a while, then it will clear up. These are the known problems right now: exhaust leak at manifold, possible leaky injector when hot??, and the fuel pump is noticeably loud when it's acting up. I checked fuel pressure and it's around 35-38. There are no vacuum leaks. I've done the intake gasket also. It has 209,500 miles on the original engine and transmission. Thanks guys for any help! I've also replaced the IAC valve too.
