I have a 2003 hyundai elantra, first was fine then all of a sudden my car rpm would go high when in park or low and sometimes turn over idling withe my foot in the break, check engine light would come on and off and if I went into a fast food line, if my car Sat it would idling low and stall then turn over, well looked it up and figured IAC valve and check engine light came on and stayed, took it off clean it out and put a can of seafoam in my gas tank, took positive off battery to reset and light came off, day later came back on (getting low gas mileage btw) and after a day or two all was fine except for a high idle but it wouldn't stall our anymore, it was great to have my car back, until the cold weather kicked in and I go to start my car after a 6 hour work shift and there's ice even on my windshield, go to start it and it wouldn't stay on, kept trying figured to start foot had to be pressing gas and continue to do so until it warmed up, still would have VERY rough idle and hasn't really been driveable with idling problem and sometimes would turn on and sometimes not, well I thought maybe motor in iac was going bad so I ordered a new one and put it on, reset battery again so check engine light was off, drove for 2 minutes with it great then after that check engine light flashed on, not back on yet but having the same problem wheb idiling slow (turning into my garage) turns over and stops, have to put in park and turn key again, keeps doing it, any ideas on what it could be I'm dying for help, I'm a 17 year old working and can't afford a shop and I need my car for my job