Elle

"Michael Pardee" <michaeltnull@cybertrails.com> wrote
> Old time coils practically never
> failed; like the old Mopar slant 6s, they didn't have the
power to blow
> themselves up. Modern coils run at much higher power and
are no longer oil
> filled, so failures are not unusual. My experience with
electrical parts of
> all sorts shows the pattern that power handling devices
gradually cook
> themselves one way or another. 200K+ miles on a coil
certainly puts it in
> the range of "untrustworthy," and when a contributor I
respect says she has
> seen intermittent failures in them before they die I think
that's reason to
> change it out on suspicion... while still investigating
other possibilities.

Toss in that Tegger put this item's troubleshooting and
replacement, with quite a lot of detail, into his FAQ.
Meaning the coil's failure is reported quite a bit here.

My 91 Civic's first coil lasted ten years, 120k miles. My
one non-OEM coil lasted less than two years, about 35k
miles. Firestone charged me an arm and a leg for that
non-OEM coil, too.

'Course, let me be the first to point out that non-OEM
ignition wires may have played a role. Tegger's 1991
Integra, at over 240k miles IIRC, is still on its original
coil. He appears to take fastidious care of his ignition
electrical parts (rotor, cap, wires, plugs all replaced at
five years by him, all OEM IIRC). A lesson for us all, IMO.

I read the other day an article by Auto tech writer Larry
Carley. He also reported that not taking good care of
ignition wires will shorten coil lives.

This might not solve your daughter's car's problem. Again,
it's just where I would start. Though I would have taken
resistance measurements, per the manual's specs, on the old
coil before replacing it, too. Not that you have time over a
possible holiday to deal with this.

Jim Yanik

"Elle" <honda.lioness@earthlink.net> wrote in
news:EZ3sf.898$M%4.332@newsread3.news.atl.earthlin k.net:

> "Jim Yanik" <jyanik@abuse.gov> wrote
>> "Elle" <honda.lioness@earthlink.net> wrote
>> > "Jim Yanik" <jyanik@abuse.gov> wrote
>> >> "Remco" <whybcuz@yahoo.com> wrote
>> >> > Yeah, that is kinda weird how they have the tach
> input
>> > coming from the
>> >> > ignitor. One would imagine they could have just as
>> > easily taken the
>> >> > signal going to the ignitor (possibly current boost
> it a
>> > little) and
>> >> > feed it into the tach directly. Less wire and things
>> > that can go wrong,
>> >> > imo...
>> >> >
>> >> > Maybe they did that as a trouble shooting measure or
> we
>> > can use at as
>> >> > such: This morning I cranked my wife's integra and
>> > noticed that while
>> >> > cranking the tach moves very slightly. Maybe if a
> honda
>> > cranks and the
>> >> > tach does not move it is an indication that the
> ignitor
>> > is bad..? That
>> >> > would be an interesting thought.
>> >> >
>> >> > Wonder how Michael is making out with this thing.
>> >> >
>> >> > Remco
>> >> >
>> >>
>> >> I doubt a starter will crank the motor fast enough to
> make
>> > any significant
>> >> reading on the tach.
>> >> What's the smallest RPM indication on the tach,100 RPM?
>> >> No starter turns the motor that fast.
>> >
>> > Doesn't this assume that it's mechanical motion of the
>> > crankshaft or camshaft that actuates the tachometer? If
> so,
>> > I'm not so sure I buy your reasoning.
>>
>> But during CRANKING,the ECU reads the crankshaft
> (CK)sensor to determine
>> firing pulses to FEED the igniter.So,tach pulses are still
> dependent on the
>> ECU and engine RPM.
>> >
>> > I thought it was strictly a digital signal from the
> igniter
>> > (in particular, its computer chip) that actuated the
>> > tachometer. That is, the igniter computer chip certainly
> is
>> > not actually sensing degrees of crank- or camshaft
> rotation.
>>
>> No,the crankshaft sensor is doing that.
>> Spark plugs fire -at a certain position of the piston in
> each cylinder-
>> ,determined by the ECU,thru the CK sensor.Not by RPM.
>>
>> > Instead it receives signals from the ECU to excite the
> base
>> > of the igniter's transistor yada, in proportion to the
> rate
>> > at which the primary of the coil is supposed to be
>> > energized. This of course determines the plug firing
> rate,
>> > which will certainly determine, ordinarily, the engine
> RPM.
>>
>> You have it backwards.
>
> I just omitted the effect of the CK sensor. The main
> point--that the signal to the tach is digital

Meaning there's ON and OFF and no inbetween.

> and in
> response to the ECU signal, and may be sufficiently
> electronically yada noisy to yield some jiggling of the tach
> upon starting--stands.

The jitter would be due to normal timing variation of firing pulses from
the ECU/CKsensor system,not from "noise" which would not affect a digital
signal.(after all,it's a closed-LOOP system.)
And the inertia of the digital to analog conversion to drive the tach
needle smooths out jitter.
The tach jitter is essentially meaningless,as the motor is not turning fast
enough to give a true indication of RPM,RPMs being below the minimum
calibrations of the tach dial.
Note I previously said "significant reading".

>> >> I doubt a starter will crank the motor fast enough to
> make
>> > any significant
>> >> reading on the tach.
>> >> What's the smallest RPM indication on the tach,100 RPM?
>> >> No starter turns the motor that fast.

Actually,I think the RPM calibration begins at a few hundred RPM,then
linearly increases from there.
>
>> On *starting*(cranking),the CK sensor reads engine
>> crank position,and the ECU reads that and calculates the
> triggers for the
>> igniter.The starter determines the cranking RPM,the ECU
> reads it thru the
>> CKsensor (piston position)and triggers the igniter,where a
> supplementary
>> signal is tapped to run the tach.
>
> Yeahbut while starting, well within one camshaft revolution
> the ECU is signalling the igniter, whose computer chip is
> still signalling the tach.

(well,the igniter chip is not a "computer" chip,it's analog;a current-
sensing comparator to insure a full coil charge,that "dwell" stuff.)
>
> I'm just saying ISTM there's some kind of signal to the tach
> being generated, starting well within one camshaft
> revolution.

Yes,the tach pulses get generated,but not enough pulses or fast enough to
be significant.I haven't gotten a look at the specific circuitry of the
igniter IC to be sure that tach pulses would not be generated even if the
Darlington was blown and no current being switched thru the coil.The ECU
could be triggering the IC and tach pulses passed on,but no Darlington
drive or a dead Darlington.

>
>> BTW,the igniter fires the coil *4 times* for each
> revolution of the
>> crank,
>
> I believe you mean for each /two revolutions/ of the crank.
> It's a four-stroke engine; takes two revolutions for each
> piston to have gone through firing TDC (in a four-cylinder
> car) once; etc.
>
>

You got me there.

--
Jim Yanik
jyanik
at
kua.net

Elle

"Jim Yanik" <jyanik@abuse.gov> wrote
> "Elle" <honda.lioness@earthlink.net> wrote
> > I just omitted the effect of the CK sensor. The main
> > point--that the signal to the tach is digital
>
> Meaning there's ON and OFF and no inbetween.
>
> > and in
> > response to the ECU signal, and may be sufficiently
> > electronically yada noisy to yield some jiggling of the
tach
> > upon starting--stands.
>
> The jitter would be due to normal timing variation of
firing pulses from
> the ECU/CKsensor system,

Sure. I was being loose with "noise" and probably crossed
the line to inaccuracy.

> not from "noise" which would not affect a digital
> signal.(after all,it's a closed-LOOP system.)

AFAIC, noise can be a problem, regardless of whether the
system is closed loop or open loop.

For example, the ignition system has a radio noise condenser
in it (meaning, I hope as you know, this condenser reduces
interference with the ECU, the car radio, and probably the
igniter's transistors. Reports from two of our regulars here
are that this condenser's removal or aging can definitely
adversely affect ignition and so engine performance.

> And the inertia of the digital to analog conversion to
drive the tach
> needle smooths out jitter.
> The tach jitter is essentially meaningless,as the motor is
not turning fast
> enough to give a true indication of RPM,RPMs being below
the minimum
> calibrations of the tach dial.

Meaningless as far as indicating actual RPM. Meaningful as
far as possibly using it to diagnose an igniter failure. Or
so it seems to me for now.

I don't agree or disagree with the rest. My only interest
was proposing that the Tach response could give an
indication of igniter mis-operation. No disrespect intended;
I prefer to get the bulk of my electronics lessons from
other than Usenet. It's too hard to communicate important
detail on internet boards.