Mileage issues on 98 Civic

I replaced my cap, rotor, and PCV valve with Honda parts about 4
weeks ago on my 98 civic 5spd (205000kms). I noticed a big difference in
acceleration. So I gave myself a week to enjoy the newfound peppiness,
and then started driving normally again.

However, even after resuming normal driving, my mileage is definitely
worse than it was before.

Before I got easily to 1/2 tank (23-25 liter fillup) and the trip
Odometer would read between 270 and 330kms depending on the driving mix.
(usually about 50/50 city/hwy) Now I get to about 260kms tops on the same
amount of fuel and driving ratio.

It is a little cooler out now than in summer, but its still above
freezing, so the mileage decrease experienced from the cold should not be
a huge factor yet.

I thought maybe my plug wires (about 2.5 years old) were bad. I did
an Ohm check on them, they are all around 3000 - 6000 ohms. My #3 wire
didn't even register any resistance. Could that be a problem? I pulled
that wire while the car was running, and there is definitely spark going
to the #3 cylinder.

So there definitely doesn't seem to be any problems with the
wires, but that it doesn't register resistance I thought was kinda weird.
Also, if there was a huge problem with #3, wouldn't I get a Check engine
light?

I also replaced my spark plugs last March with NGK plugs from a
Reputable parts store. I looked at them today, and they still look fine.
So no probs there.

Also, when I did the PCV valve, I noticed that the old one (which
Has probably never been replaced) was still functioning perfectly. A
Little gummed up, but still had that rattle when I shook it.

In my previous experiences, when a part is replaced due to wearing
out, generally the problem shifts to another problem part, until you
replace everything and it finally works properly. In this case, I'm
pretty sure I've done everything I can. Am I missing anything?

 

Weird, yes - there definitely is something wrong with that wire!
It's internal conductor has started to disintegrate and has formed
a spark gap, thus preventing your Ohmmeter from measuring
a sensible reading. However, the HV spark can still jump that gap
and fire the plug.

Replace it and the others too since they will follow soon, surely.

Not neccessarily because the plug is still firing but at reduced energy.

 

My gas consumption has gotten worst, but only by about 1%. Instead of
getting 6.4L/100KM combined hwy/city, I'm now getting 6.7L/100KM. I expect
about 10% reduction as winter progresses.

From my experience, some of the causes for the poor winter mileage are:
Winterized gas which will return about 2% reduction in fuel efficiency. If
you're using premium instead of regular fuel, that would be another 2%
reduction. Then there's the colder weather which could add another 2% to 5%
on your mileage consumption (depending on the amount of cold start-ups per
day). And to top if off, there's the heavy snow tires which have poor
rolling resistance...

Pars
98 DX Hatch

 

I would replace the spark plug wires (as was mentioned) but I would
also recommend getting your spark timing checked. If your timing is
out, it is one factor that can affect your fuel consumption.

-k

 

Check and maintain tire pressure too, if possible at least every two
weeks. In my experience, tire air pressure varies more with seasonal
temperature changes.