Hey,

This is mostly for those that were following an earlier thread about my
idle fluctuating in my 1991 Civic Si. I had said that the bleeding
appeared to fix the problem and it did intially. However, I hadn't taken
the car out for a good 100 mile hwy. cruise. The bleeding definitely
helped, but after a long cruise averaging 77 mph, and then putting
through a town I got the 750-1250 RPM fluctuation again. It wasn't as
severe as it was prior to the bleeding.

I want to clarify about how I did my bleeding. I didn't really want to
screw around with draining my rad. and refilling it, so I started the
bleeding attempt with the car when it had been driven up to good
operating temp. (I live in Wisconsin, USA  20-40 F lately) and allowed
to cool for at least an hour (still above ambient temp.) for convenience
sake.

I took off the rad. cap and started the car. The rad was full right up
to the cap and my reserve was at its normal level. I don't think I have
any cooling leaks. I guess I can't remember the exact order I did
things, but I had written the directions from the UK Honda manuals for
the 91 CRX and the 91 Concerto (extremely similair if not identical). I
definitley got a lot of air out, but I could always get more out (or so
it appeared - my description is in the earlier thread).

So, this last weekend I had a chance to do a little work on the car and
did my valve lash that I had wanted to do for a long time, and also put
in a new oxygen sensor. My valves didn't seem to take much adjustment. I
had really wanted to do this since I had found my timing belt to be off
by a tooth during the summer and wondered if the valves would have been
stressed more.

After the work was done the car's idle problem returned, with the
fluctuation happening at a higher rate than before, and the idle seeming
to be higher than normal. When I bought the car I didn't like how it
idled, and broke the seal on the adjuster screw and dialed it up, CCW
(allowing more air in?). I had also fidgeted with it a few more times as
I have performed maintenance on the car. I just dialed the adjuster
screw tighter, CW and now I've got a really nice idling car with
noticeably better gas milage so far.

I also tried bleeding some air again when the car had been driven to
operating temp. after doing the 02 sensor and the valves. I couldn't see
any air coming out after opening up the bleeder a acouple times. I don't
know why I seemed to always continually get air last time. I might have
opened the bleeder to far previously.

So I guess I would say from experience now that it may be worthwhile to
replace an oxygen sensor on a high mileage (136k) old car. Maybe the new
02 sensors last longer. I read a really good writeup about 02 sensors on
Bosch's website.

I sure hope I'm done with maintenance for a while because winter is
coming and its tough for me to find a situation to work on my car during
the season. I am also hoping I can break 40 mpg. I used to be able to do
it easily in my '91 DX sedan, but I've only gotten high 30's in my Si
(understandably).

Thanks for all the help along the way,

Mark