Before you do anything else, I would look at the idle air control valve like sbourg said. I have a 190E and I took it out and cleaned it as well as I could with brake parts cleaner, then lubed it with WD-40. I haven't had a problem with the idle since. IT's kind of tough to find it if you don't know what to look for, but it's the pump looking thing encased in a rubber "Holder" sandwiched between the 3rd and 4th intakes. Email me if you don't find it. Just yank it out