CIS Mixture adj/Gunson/Question
 

Hi,

I just hooked up my Gunson, found out I was at about 1.2%CO, maybe lower.

I was the one with the glowing exhaust manifolds. I adjusted the mixture (It didn't click like the 101 Proj. book said??) and seem to have boosted it up to 3.5%.

Now I'm wondering this--the idle after adjustment seems to steadily fluctuate between 1000 rpms and 1500 rpms. (Happens every 3-4 secs maybe). Has anything gone wrong?

Oh yeah, I'm still getting a small flame from where my heat exchanger and the manifold meet up. I'm ready to cut those SOBs' off! Luckily I don't have thermal reactors. I'll have to re-test tonight when its dark to see if the manifolds still glow...

maybe a vacuum leak somewhere; also ensure you calibrated your gunson with clean air not with the car running. I thinks you cal. to 2%, but yours may be different. you may want to check fuel pressure from the warm up regulator, to ensure your fuel pressure is fine at the various temperatures.

Kris, it's normal to see this kind of oscillation during tuning. It just means the mixture is too rich.

Doug
75 911S

Thanks. Looks like it's running fine now after tweeking. Installed a new WUR last month and checked all fuel pressures. They're good.

How did you connect your gunson tester? I just bought one for my 82 SC and the probe is too big to fit in the test port on my exhaust? I'm trying to kluge up an adapter for it.

Regards,

Jerry Kroeger

I just wore a work glove and held it in there. I was thinking the same, it doesn't stay put. If you come up with anything let us know! I'll brainstorm too...

BTW, I set it for about 3.1% (+/- 0.5%) and it seemed too rich. (The idle was searching at 1k to 1500k rpms) It doesn't seem as accurate as I thought, even with going through the calibration procedure (am I understanding this-- 0.5% accuracy is a LOT when talking about such a small range of numbers...

I tweeked it just a hair and seem to be getting a nice idle.

You may want to try adjusting the idle screw up and get that o2 mixture down. I think you'll notice a big difference

I tried turning the idle screw and it didn't really respond??

how far were you able to turn the screw??

You may want to try turning the screw then giving it some gas. With this you should notice the change

Thanks. I'll try that. I'm not turning the screw a whole lot--is it sensitive, or does it take a few turns? I was just adjusting it like 180 degrees...

I would start the process by leaning the o2 mixture out. Out to the point that there is a delay after giving it gas. Now go rich 1/4 turn at a time. after each turn remove the adjustment tool and give it gas. It should immediatly rev up and then right back down. Once this happens you can lean it out that last 1/4 turn and make even smaller adjustments !/16 turn in order to really dial it in. Once you have done this. Turn that idle adjustment (BIG SCREW) counter clockwise to raise your idle speed to right around 1000 rpm in neutral. Mine now idles at 850rpm in first gear with my foot off of the gas.

I think I've got it... A good fuel mixture, good idle.

I re-checked the timing and found that it was about 15 degrees. Bumped it up to 5 degrees, didn't check at 6000 rpms (I should). Readjusted idle.

Fuel mixture should remain the same, correct?

Thanks

The fuel mixture should remain the same.