Fuel economy loss

I have a 98 civic si and I was getting 525km per 40 litres in the
city.
Over last year the fuel usage has gone up and I can't figure out why.
Currently I am getting only about 450km per 40 litres in the city.
My idle is fine and the engine does not seem to run roughly.
I have noticed that around 2500 rpm I used to get a little surge of
power and then again at 3100 rpm.
As of the last while the surge of power at 2500 rpm is intermitent. I
would suggest that the power seems to go away with the engine getting
to running temperature however I have no proof just how it seems to
me.

Anyone have any ideas of what might be the difficulty.
I can tell you I have never replaced the PCV valve in the last 100,
000 km. Oh and the car currently has 190, 000 km on it.

Thanks for any help,

Brian

 

See the tips and discussion at
http://home.earthlink.net/~honda.lioness/id11.html

 

Well, there are many factors.
1. Your cylinder compression may not be that good any more due to
higher KM.
- when the car warms up the oil viscosity goes down and because
rings don't seal as good as when the car was new, there is power loss.
Notice that good pickup just before the engine has completely warmed
up.
2. The transmission is not as responsive as it used to be i.e. it
switches to longer gears much sooner. So when you are going 60KM per
hour in the 4th or 5th gear car feels lazy, and takes a while to
upshift

I am not sure what you mean by intermittent. Sounds like ignition
problem, maybe spark plug problem, contaminated fuel delivery system,
injectors etc.

Does the engine run quietly or can you hear a lot of different
mechanical noises?

Dan.

 

First off thanks for the post Dan,

Sorry I forgot to mention it is a standard.

The car is quiet except for a slight squeak when there is high
humidity. What I mean by intermittent is that sometime when I am
driving and I get to the 2500 rpm point I feel the little power surge
and then sometimes I don't. Usually once the car is up to running
temperature I find that surge of power is no longer there.

Any ideas? I can definitely look into the compression of each
cylinder. What does everyone recommend for cleaning out fuel
injection systems?

 

Compression tests are normally done when the engine is cold.

I did a test on my 98 civic (not a vtec) about a year ago, It had 250000kms
on it. I got 190lbs of compression (+/- 4-6 lbs) on all cylinders. That is
indeed the factory compression.

However, to get a better picture of the condition of the rings, how well they
are sealed, as well as the valves and how well they are sealed, you need to
do a leakdown test. Any competent honda mechanic should be able to help you
with this. Then you can determine whether the problems you are having are
valve related or cylinder/piston related.

Its a special tool that you plug into the spark plug hole on a cylinder with
both valves closed. You then run compressed air through the tool, and it has
a scale on it to tell if the level of leakage is acceptable (using Red-Yellow-
Green criteria with an actually CFM rating to quantify the level of leakage).
Also, you can tell where the leakage is occuring... if the air is leaking out
of the intake, it means your intake valves are not seated properly. Out of
the exhaust means exhaust valves. Anywhere else, probably means piston rings.


I did perform this test on my 93 Nissan Altima before I bought it from my
brother. It leaked like a sieve through the intake, and the highest
compression I could get out of any cylinder was about 85lbs. Kinda funny too,
because the car actually seemed to be running quite well. I poured some
Lucus Oil Upper cylinder cleaner into the fuel and drove the *(&^ out of it
for about a week, and performed the same test. Now I have 160lb compression.

I have not performed the leakdown test on my civic as yet.

So you can try the Lucas Oil stuff (available at your local canadian tire or
partsource, I assume you are in Canada if you are talking KMs), or try to
find Chevron Techron fuel injector cleaner. Many people on this group have
had great success with that product.

As far as fuel economy on my civic, normally I get about 450-500kms on 40L of
fuel, mostly highway driving. Now have 282000kms on the motor. (its a 5 spd
too). Keep in mind that mine is not vtec though, and that does make a
difference (vtecs use more, generally speaking)

t

 

This mileage seems quite low for the 98 Civic with manual tranny (it
translates to about 28-29 MPG). Was it that bad when there were fewer
km's on it?

Serban

 

nope, was much better. My wife drives it with a heavy foot though.

 

Thanks for the help folks.
I am going to try the Lucas oil upper cylinder cleaner then do a oil
change and put in a new PCV valve at the same time.
Hope that fixes it and if it doesn't I will go with some of the other
solutions. Such as checking the compression, etc.

 

Another relatively cheap thing to try if you're not already doing it
is to switch from 5w20 to 0w30. It should be synthetic as rings seal /
work better with synthetic due to the uniformity of synthetic
molecules. I have a 2003 Accord (4 cyl) with just under 320,000Km and
I use Amsoil 0w30 from 44,000Km. The engine is not maintained by any
Honda / mechanics shops. The reason I switched from 5w20 to 0w30 is as
follows and I will mention only the ones that may relate to your
dissatisfaction. The main reaon to switch for me was cylinder assembly
wear and tear. No matter how often you change your 5w20 honda motor
oil, the viscosity at the optimum operating temperature is
approximately 10% less than with 0w30. Since I am a little more
heavier footed than most drivers it means that the internal cylinder
moving parts could on occasion exceed the temperature range and enter
in the "danger" zone for the 5w20 oil i.e. viscosity below 7 or even 6
(i.e. it is about 9 for 5w20 Honda oil at normal operating car
condition i.e. hwy cruising between 90-100Km/hr). So the film becomes
very thin until the water cools down the system, and eventually the
viscosity increases back to 9. With 0w30 you have that extra viscosity
capability at higher internal temperature. The end result is reduced
engine wear when you are pushing the engine. I change the oil and
filter every 32,000Km. Prior to oil change I drive the car with higher
RPM on occasion (5-6k RPM) to burn carbon / film etc. if any is there
(most likely nothing there). I then drain and fill it with 5w30
Autolab (cause it is cheap) fresh oil and run the engine for about ten
minutes to wash it. I drain it and refil with synthetic. Does all this
work well? I have done this on every car I've had since mid seventies
on same oil (Amsoil. It doesn't have to be Amsoil - key here is
synthetic). I am a bit surprised at the gas milage that you're
getting. At 320,000Km Accord at 100Km/h I use between 5.8 and 5.9 l of
gas per 100 kilomteres i.e. over 1000Km per tank (I only do hwy
driving). If you eventually perform a compression test and fiind out
that compression is low due to rings, you may try 0w40 synthetic. that
has even better sealing properties at normal and higher engine working
temperature. The negative effects of higher viscosity oil at normal
operating temperature is higher fuel consumption.

Good luck.

Dan

 

On Civics the standard oil is 5w30, not 5w20.

To be honest, i have neglected the civic for the last 2 years at least. I
will probably do some of the same as the OP, new PCV from Honda, check timing.
I think I'll do a brake check too, perhaps one of them is binding and causing
my mileage to drop...

Couple other things too, a bolt on my valve cover is busted, need to fix that.
.. its just sitting in there with some RTV sealant around it to prevent crap
from getting in. Snapped bolt on distributor cap. Not sure if that will
affect anything. Check all idler pulleys and accessories.

I was kinda hoping to wait to do this at the next Timing belt change (coming
up next summer), but i have some time now, so it's proabbly a good idea.

t