This started about 3 days ago. When shifting gears (manual trans), at most the motor will go down to 1500 rpm. When you pull to a stop light and push the clutch in, it will go down to 1500 rpm and stay there until you stop. Then it will stay at 1500 rpm then drop down to 1100 after about 4 seconds. Used to idle at about 800-900. Any thoughts? Clean the IAC?

 

Clean the IAC then start checking vacuum lines.
Also read the codes,there may be one caused by a vac leak that doesn't throw a CEL.

 

Currently there isn't any codes but I did have a P0442 with is a small leak in the EVAP system. I'll clean the IAC this weekend and see any noticable vaccum leaks.