So I'm getting these two codes now, the first seems to happen after 20 or so minutes of driving and saying it's a cylinder one misfire...and the second is something about my tstat I think? Anyone have any experience getting these two codes to go out? 04 Pontiac grand prix gtp comp g 148k miles...I just did a coolant flush and added a 180tstat so the p0128 I guess is expected but just wanna be sure the system is not getting messed up because of it? And for the misfire one I don't know what to think really? Ordered new plugs wires and a coil and going to start there unless someone knows exactly what this may be? Are they possibly connected? Didn't have this problem when I first drove it home over 30 miles. Then two shorter drives after new tstat I get the misfire..