[MichiganMat]

Gents,

I finally installed a wideband O2 sensor and gauge in my car last night (3.0SC with CIS) and *boom* engine issues solved in 15 minutes. The car was running extremely lean. I've searched the threads on this site for years trying to figure this out and Im so happy to have it fixed that Im going to shout it from the rooftops.

A few things I've learned:

While running lean:
- the car would buck and surge badly around 2K rpm.
- the engine was extremely sensitive to pedal movement in the 2-3K range, especially in traffic
- the engine struggled to hold idle and was difficult to start
- I could hear the engine missing / misfiring / stumbling in the exhaust note while at idle and cruise,

With the gauge was installed I was able to fatten up the mixture and saw:
- as the mixture became more rich, the idle went way up
- I adjusted the idle down using the large idle screw on the side of the CIS
- Car now idles perfectly, bucking @ 2K is gone, and misfiring is gone, and the engine starts much easier

I did attempt to over-richen the mixture and experienced:
- lumpy idle, or "seeking" idle, 850 to 1200 rpm
- backed off the mixture by 1/4 turn and it smoothed right out

The engine is now at a point where the idle is stable, not lumpy, and the bucking issue is resolved. However, my LM-1 gauge is telling me that my full-throttle / acceleration AFR is ~15.4. Cruising AFR is better at around 14.5. This is a bit more lean than I was hoping to see. Like I said above, I did try to fatten it up but it negatively effected the idle behavior. So still a bit of work to do, but I feel like Im on the right track.

So, in short: Buy a LM-1, haha.