Update, Regarding Idle Issues

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

 

Did you put the heat on max-heat, squeeze some tubes and
thermostat not upside down? Disconnect the EACV and startup
the car. If idle is still high then the fast idle or leak is letting in air.
If it's at 650 then cold sensor and such is bumping up idle.

 

I can't quite tell from your post: Is the idle problem now fixed? If so, do you
think it's because you installed a new oxygen sensor?

 

The idle problem is fixed. I think it was a mixture of 3 things, each
probably having its own effect. Depending on the order I addressed
things my results may have varied. The three:

Air in my coolant

02 sensor

Idle adjusting screw turned up at least a couple full turns too much
--for a car without air in its coolant and with a new 02 sensor--

I could have gotten away with keeping my old 02 perhaps if I had just
adjusted my idle after the bleeding, but it was not apparent that this
could be a solution at the time. Once I did my valve lash (unrelated I
imagine) and my 02 sensor, it became apparent to me that my idle was set
too high with the srew. I do not feel bad about replacing the 02 at all.
The car seems to run noticeably better with it, especially with regards
to how it reacts to changes in throttle opening. I haven't driven it
enough yet to get a good idea what my 'new' gas mileage is going to be.

Mark

 

Indeed. And now you have an emergency spare.

Interesting diagnosis and troubleshooting, with so far a happy conclusion.

Perhaps it supports a "shot-gun" philosophy of automotive repairs: Fix all the
cheap (and probably due for replacement/adjustment within a year or so anyway)
stuff possible, then go looking for deeper problems.