Mixture question

[Scott R]

I was setting my mixture today, and I tried to set the mixture to 0.8 which is what the rear decklid said using my Gunson tester, the car runs..... not great however. I searched a dozen or so old threads and found John Walker's suggestion of setting to 3.5% and disconnecting the O2 sensor, this works great, the car idles smooth as glass.

So my question is, what's wrong? And how should it be set? I hate to think I need to have the O2 sensor disconnected, and BTW it's a brand new O2 sensor.

I should also add, new air box, complete reseal, intake runner gaskets, runner boots, WUR and freq valve.

[Scott R]

Sunday morning bump, anyone?

[Paulporsche]

It's possible there isn't too much actually wrong w/ your car...it's just that they run a lot better @ 3.5%.

Having said that, however, what symptoms were you having?

Also, isn't it true that these Gunson analyzers are only accurate to .5%

[Scott R]

Originally posted by Paulporsche
It's possible there isn't too much actually wrong w/ your car...it's just that they run a lot better @ 3.5%.

Having said that, however, what symptoms were you having?

Also, isn't it true that these Gunson analyzers are only accurate to .5%

My 911 is running at .8 with the 02 sensor plugged in, and it runs as well if not better than ever, this after a complete CIS rebuild however. It does tend to start a bit sluggish when already hot with it at .08, nothing terrible just about 100 RPM's lower than normal idle, then it comes up pretty quick.

At 3.5 It feels gutsy and has more power at take off, I can see why it's popular to bump it up, I just can't stand anything "unplugged" in my engine bay, especially after the major effort I have gone through to get everything sorted and put back together.

Most of my issues through this entire rebuild can be tracked down a poorly adjusted sensor plate, the plate was sitting so low that without the assistance of the CSV, oe priming the injectors it was almost impossible to start. I am however still missing the start it cold and have the RPM’s up around 1200, then down to normal. I’m not sure which mechanism controls that, and it’s on my list of things to track down.

I'm not sure on the accuracy question, I need to find that out I guess.