I have a 99 4.0L SOHC Auto. Few days ago my check engine light turned on while I was driving. It returned a P0172 DTC code (System too rich bank 1). Everything seemed to be ok though. I don't have problem starting and I don't have problem idleing like most other people having similar problem. It's been pretty cold here these past few days too.

Can somebody give me a clue what to look at first. I've read about the IAC, MAF, lower intake gasket but again I'm not having problems starting nor idleing.

Thanks.