ignition timing question

hi, I just want to check someting:

suppose the car has distributor-style ignition (not electronic!) and
there is no knock sensor (1997 Civic LX)

If there is carbon build-up, and ignition occurs too early (due to
higher compression ratio), using a higher octane should help, right?
changing timing might not hlp, because the fule might ignite on its own
(detonation?).

If, on the other hand, there is no carbon buildup, and the timing is
advanced too much (from the distributor), then the ignition occurs due
to the spark plug, and it occurs too early, no matter what octane you
use, right? in this case you need to adjust the timing to get rid of
pinging, using a high octamne does nothing.

I am asking because even though I do not have a timing light yet, I
tried to "adjust" the timing on my Civic (maybe the proper way to put
it is "change" rather than "adjust"). Anyway, I rotated the entire
distributor back and forth, but i have not noticed a significant change
in that sound I believe to be pinging. I could feel the engine loosing
power, but when I drove the car I got roughly the same "pinging"
sound... maybe it is not pinging after all. I put the distributor back
to where it was, and I plan to get a timing light soon, or at least
take to a mechanic for proper ignition adjustment.

next I plan to replace the PCV valve, the mileage is terrible (25 city
30 highway) and I drive very gently. I just replaced the spark plugs
with OEM, and checked and cleaner the rotor, cap and wires (all were 5
to 10K). I also run some TECHRON...

My other Civic (2001) gets 30-32 City and 36-40 highway and I drive
much more aggresively. With the gas prices soaring, It makes sense to
troubleshoot this problem on my 97 Civic.

Thanks

chibitul wrote:
> hi, I just want to check someting:
>
> suppose the car has distributor-style ignition (not electronic!) and
> there is no knock sensor (1997 Civic LX)

the 97 is fully electronic. it has a "distributor", in that it has a
rotor arm and single coil, but the spark management is all electronic.
it does not have a knock sensor.

>
> If there is carbon build-up, and ignition occurs too early (due to
> higher compression ratio), using a higher octane should help, right?

not unless you have a seriously coked up engine. and even if you do, a
couple of hours rodding that thing at full throttle up the steepest
hills you can find will work wonders to clean it out. the honda
combustion chamber design is actually fairly knock resistant - it takes
a lot to get it to do it, and even then, it'll usually be a symptom of
some other fault.

> changing timing might not hlp, because the fule might ignite on its own
> (detonation?).

what mileage? octane does not affect carbon buildup. gas quality does,
air filter cleanliness does, spark efficiency does, oxygen sensor does,
big time. and even if your air filter is clogged, that'll reduce knock
because the mixture goes rich, not lean. too lean is a common precursor
to knock.

>
> If, on the other hand, there is no carbon buildup, and the timing is
> advanced too much (from the distributor), then the ignition occurs due
> to the spark plug, and it occurs too early, no matter what octane you
> use, right? in this case you need to adjust the timing to get rid of
> pinging, using a high octamne does nothing.

do *NOT* mess with the timing. set it to factory spec & LEAVE IT! the
ecu on the 97 does some sophisticated math based on a number of sensor
inputs to calculate timing. if you set the sensors wrong, what you're
doing by bessing with the distibutor, you could have an expensive
failure on your hands. again, set it to factory & leave it.

to answer your question, on a car set for high octane, it will spark
earlier than one set for low octane, but that is a function of slower
combustion speed for higher octane. so, yes, if it's too far advanced,
increased octane will not "help". ignition timing should always be
set at factory and not "adjusted" for fuel grade - the ecu & honda
engineers have a much better idea of what works best here than you or i.

>
> I am asking because even though I do not have a timing light yet, I
> tried to "adjust" the timing on my Civic (maybe the proper way to put
> it is "change" rather than "adjust"). Anyway, I rotated the entire
> distributor back and forth, but i have not noticed a significant change
> in that sound I believe to be pinging. I could feel the engine loosing
> power, but when I drove the car I got roughly the same "pinging"
> sound... maybe it is not pinging after all. I put the distributor back
> to where it was, and I plan to get a timing light soon, or at least
> take to a mechanic for proper ignition adjustment.

pros mark the distributor against the housing so that even if the
distributor is removed completely, it can be replaced to the same
timing. the timing light is to confirm it was done right or to set a
new component if complete replacement is required. never mess with the
timing on any vehicle unless you have the tools to re-set it right.

>
> next I plan to replace the PCV valve, the mileage is terrible (25 city
> 30 highway) and I drive very gently. I just replaced the spark plugs
> with OEM, and checked and cleaner the rotor, cap and wires (all were 5
> to 10K). I also run some TECHRON...

pcv valve, air filter, thermostat, oxygen sensors, egr [if present],
etc. read tegger's faq's. sometimes, "cleaning" distributor caps
leaves partially conductive film inside, so replacement is a better
policy. any doubts on anything much over 60k, replacement is the safe
choice. same goes for leads. NEVER clean plugs yourself unless you
have one of those abrasive blower machines.

>
> My other Civic (2001) gets 30-32 City and 36-40 highway and I drive
> much more aggresively. With the gas prices soaring, It makes sense to
> troubleshoot this problem on my 97 Civic.
>
> Thanks
>
with respect, i don't recommend you do more work on this car yourself
unless you get some more theory & practice under your belt. signing up
for a local car maint class would be the best way to go. you can easily
do a lot of expensive damage to a modern car if you don't know what
you're doing.