Finally found my cold idle issue

[Funracer]

Been through by engine systems thoroughly in the last year. Lambda system, valve adjustment, fuel filter and fuel pump, rebuilt and calibrated WUR, plugs, wires, rotor, timing, vacume leaks, mixture changes, and on and on, the things we all do to get our cars to run as they should.

This is my first 911 and I really felt that something was missing. After all that tinkering the car still had a rough cold idle and rev response from 2500 to 4000 rpm was flat. I had pulled the fuel injectors months ago when I replaced the injector seals. I did a rough test with an air compressor at the time that showed they all flowed and that they opened at about the same pressure. Looking back on it they flowed but were not misting as they should . I failed to recognize this at the time.

Found a good deal on injectors and installed 6 new ones yesterday on a rainy day.




When I tried to start the car it cranked for a long time and finally started, ran poorly and conked out. Backed off the mixture screw, got it running enough to warm up and reset the mixture and idle. It was running perfectly when I quit for the night, but that was not unusual as it normally ran ok when warm.



This mornings cold start was the best cold start since I have owned the car. Nearly perfect cold idle then transitioned smoothly to warm idle. I could tell right away it was running better than ever. Took it for a spirited drive and could not get the smile off my face. All the things I have checked and done in the past have helped this car run better or made it more reliable. But this has actually fixed the car. Rev response is fantastic now. The engine feels lighter and it flies through the rev mid-range.

Man this car is fun! Now on to those pesky oil leaks and a new exhaust.

[RarlyL8]

Good for you!
I've always been an advocate for not cleaning injectors but replacing with new. The engine runs so much smoother.