Car runs ok all day but in afternoon engine light comes on. It can happen faster if the air is on. When this happens; I get rough idle. Have not checked codes.

engine light flashes ???? Your best bet , take it to a qaulified repair shop , right now , damage the catalytic converter is happening .
Flashing check engine light CarMD

Chrysler Sebring Questions - Car running very rough ...

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CarGurusMar 27, 2011 - It seems after car gets to a certain temperature it runs very rough. ... 2011 at 12:16 PM about the 1998 Chrysler Sebring 2 Dr LXi Coupe ... it.one day it washot out and it was running sluggish with rough idle.and ... I changed the altnator and battery its runs like its brand-new.now ... 2002 Chrysler Sebring LXi.

Chrysler Sebring Questions - Engine Power Loss After Car ...

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CarGurusNov 3, 2011 - Engine Power Loss After Car Is Warmed Up - Major loss of power after car has ... When vehicle is cold runs ok, sometimes a little rough but not bad. Full power. Allowed vehicle to run for over 45 minutes last night at idle, died on its own, car sat approximately 20-30 minutes. ... 2002 Chrysler Sebring LX.

* Chrysler Sebring/200 Convertible Club * • View topic - Rough ...

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Dec 29, 2006 - 5 posts - ‎3 authors
However, the vehicle still suffers from rough idle under certain conditions: ... been resolved (I don't think he noticed that it happened only when warm though). .... The test will tell you its general condition without having to dig it out of the fender, ..... Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group rough ...
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May 24, 2010
Low idle rpm
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Mar 8, 2007
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run fault codes and look for a fuel supply sensor/servo failure. The heat is affecting the fuel system and is causing a fuel vapour lock or is over pressuring the injectors.

This what I think is happening. Your engine is running rich because the ECM thinks it has too much air and so injects more fuel. When you now introduce air, by taking th e vacuum line off, the fuel mixture is now more balanced. Have you cleaned your MAF sensor? Also make sure your engine coolant is full.

Could be a idle air problem. The injector could be leaking when you shut it off ..Try some injector cleaner see if it gets better..The idle air shouldnt run rough just idle real low or sometimes it will get stuck and idle high....Are you losing any antifreeze..If you are the 2.0 SOHC engine bad about leaking antifreeze into the cylinder and makes the engine run rough until it burns it out..See if you can see the smoke coming out when it happens..White smoke indicates antifreeze,,Black smoke indicates fuel..

this ussually happens if there is a transmission fault yes they are related dosent mean any major problem though could just be a sensor

bmw should NOT SHAKE THE STEERING WHEEL AT ADLE. OK SOUNDS LIKE ITS RUFF UNDER LOAD LIFT THE HOOD AND CHECK FOR A HISSING SOUND IF SO IT IS VACUUM LEAK. MOST COMMON. iF TAHAT ISNT IT LETS MAKE SURE ITS IDLEING AT 800 RPM IF HIGHER PLEASE PUT ON FORM HERE AT FIX YA AND WE CAN WORK THIS OUT CHECK IDLE, CHECK ENGINE LIGHT, AND THEY ARE BAD AT NEEDING MOTOR AND TRANS MOUNTS MY BET WOULD BE ON MOUNTS

P2176=Throttle Actuator Control System - Idle Position Not Learned
Did you use all you old sensors,or is some of them from the new engine,I would swap out the IAC sensor or check for wires not hooked up.
If it can't relearn to idle the Idle air control might be different then your old one,but its not registering with the computer

YOUR ENGINE IS IDLING LOW.MOST CARS WHEN YOU TURN ON AC THE PCM WILL INCREASE IDLE SPEED TO KEEP ENGINE FROM STALLING OUT.I WOULD HAVE THE IDLE SPEED CONTROL CHECK OUT AT THE DEALERSHIP.THEY WOULD HAVE TO ADJUST YOUR IDLE SPEED.SINCE MOST IS PCM CONTROLLED.

The best way to know what is happening there is to drive a GMC dealer and get them to hook in the diagnostic tool and read the computer memory for present faults.
Cheers