My 97 non SC has developed a rough cold idle. It feels like a misfire for the first 10-20 seconds upon initial start, idles around 6-700 rpm,then it clears up and runs fine. No problem from hot start, just cold. I did plug this weekend but no help. It had the intake done on ot 2 years ago when I bough it.
I also get the occasional P0440 engine code, I clear it with my scanner then it is fine for a few weeks then comes back on. I also put new gas cap on just in case.
Any ideas on this issue.

Thanks, Martin

moved to 92-99 Toddster

Might be your intake air temp sensor. Could be a dirty throttle body, clean the MAF, check the PCV valve, check for vacuum leaks.

Sounds like the upper intake may be leaking coolant into the cylinder(*)

Not the usual symptoms though. Usual symptoms being cold are hydrolocked motor that won't turn over, or running better than warmed up. A leaking UIM will typically spew coolant as the system pressurizes or have filled the cylinders from the pressure of having been run and shut down.

I could easily be wrong about Martman'* car. I just know that one of my previous Bonnevilles would do this and it was coolant causing the missfire. Seems the leak wasn't enough to miss hot but would leak when the car sat and cause a miss for the first 10-20 seconds of running. Replacing the UIM fixed it.

I also had one of my Bonnevilles run rough cold and a MAF cleaning fixed it.

Well, I did the plugs, wire looked original so I replaced them, tested the coils all was ok. Took for test drive and wow a lot more power. But still the rough cold idle. So I started digging deeper, and I pulled out the IAC motor and it was all carboned up, so I cleaned the intake system etc, and it is much better now. Thanks for all the good advice.