I purchased a 1986 Carrera in May of '21 and have been working my way through what it was in need of (including a complete suspension restoration). One thing that has been eluding me is the behavior on cold start. I've scoured this forum, cleaned the cold idle valve and checked the vacuum (16-17 hg, steady at normal idle, good?).
On cold start (Bosch MFI, not touching accelerator), it starts right up, but runs rough at around 500-600 RMP for about 15 seconds at which point it smooths out quickly and revs up to about 1100. Over the next 45 seconds it settles to 1000, and then over the next 10 seconds gently drops to a normal idle around 800 RPM. Does this every time on cold start.
Once the car gets about 15 seconds in, past the rough spot, I can drop it in gear and all is good, runs fine. I usually wait the minute or so for it to settle to a normal idle before I get going, though. It runs great otherwise, and starts without the rough spot when warm.
Here's the cold start video for my car showing the RPM and you can also hear the motor sound quite well:
https://youtu.be/MEli2LTVzqM
Is this normal behavior? Some guy has a video posted on Youtube called "Porsche 911 3.2 correct normal cold start idle" that mirrors the behavior of mine. Unfortunately there are no useful comments on whether this is correct or not. Here is his video:
https://www.youtube.com/watch?v=1XBg5PeARAY
Thank you.