About a month ago, I had a chevy van in my shop. It had a bad idle, missed, and ran really bad one minute and perfect the next. Using a scanner, I found the CTS to be sending a signal telling the computer it was -40 degrees one second and then it would go back to normal. As a result, one second the computer would dump fuel thinking it was cold, and then try to change to a warm reading. This vehicle did not have both codes you have, but it did say it was a rich mixture. The funny thing is no code was set for the CTS because as far as the computer was concerned, it was receiving a signal. Thus, it was working. Even though the signal was incorrect. So with that said, see if you can get your hands on a real time scanner for OBD1. The I would suggest running the vehicle to see what is actually happening.
Friday, September 26th, 2014 AT 8:00 PM