Toyota Repair: 1999 Toyota Camry, engine oil sludge, sludge problem

Question
I have a 1999 Toyota Camry LEXLE, automatic transmission,4 CYL, just under 100,000 miles.  About a year or so ago it began starting rough (not always-just occasionally) It would start but would be idling very very low, then sometimes the RPMS would drop down and it would stall out.  Every time I took my car in, they told me I was crazy (wouldn't do it for them.)  They turned up the idle and sent me home.  It has now started doing it on a daily basis, usually on the first start of the day-but not always.  It also does it usually after sitting all day at work, etc.  If I give it gas for a few minutes to keep the RPMS up, the RPM needle will eventually jump up and it will run fine...no problems while driving or if I stop and start again.  Also twice while driving my check engine light has come on, stayed on for a couple of days, then gone off again.  Of course by the time I can get it into the service place it has gone off so they can't get any codes.  I had an ignition coil problem with my 1991 Camry before this that started in a similar way but without the check engine light and with that I got bucking, stalling out at traffic lights, etc.  I'm not getting those symptoms...and everyone keeps telling me that "ignition coil problems are rare in Camrys"....since the symptoms are a little different I am hoping they are right. They have checked and replaced the plugs wires (first thing they always try) but I really don't want to spend as much as I did last time just trying to diagnose the problem.  I am wondering if the problem could be related to needing the fuel injection system cleaned?  Is there anything I can do myself to fix the problem?  I have been hearing a lot about this engine oil sludge problem in Camry's from my year and surrounding years.  I have been good about changing my oil but could that be the problem?  I cannot find any information on symptoms relating to that but do not want to risk ruining my engine so would like to stop spending all of my time TRYING to diagnose the problem and figured you would be  a good source.  Even if you aren't certain what it is, if you could give me a list of things to have my mechanic try in priority order I would greatly appreciate it!  I am getting married and buying a new house this year so I cannot afford to go to Toyota to hand over my life savings.  

Answer
This erratic idle condition is very common with camrys and other toyotas also, the problem is the idle speed control valve, also referred to as the IAC or ISC valve, it's located on the throttle body which has to be removed to get to the isc valve, the isc valve has to be removed and cleaned with a throttle body cleaner, while the valve is off the throttle body should be cleaned also with a stiff brush and spray cleaner to remove any carbon deposits on the inside, doing this fixes the problem 99% of the time providing there are no other mechanical problems like an engine misfire.