1990 civic wagon fuel economy

I have a 1990 Honda Civic Wagon, 2WD, 5-speed manual transmission.
Currently I am getting around 26mpg (9l/100km) city, and 29mpg
(8.1k/100km) highway on a good day. This seems somewhat poor to me, so
I am wondering
a) if these figures are in the normal range for a car of this model
year and age
b) what I can do to improve fuel economy?

I've checked the air filter and it seems clean, the gas cap and tank
have been replaced, and I keep the tires at 32psi (221kpa). What else
could I do to help out, and how much would it cost?

I know this question gets asked from time to time, but was wondering if
I might be able to get some more specific information.

Thanks!

 

Also the timing belt is new, the warm idle is around 1100rpm, and I
usually shift somewhat early around 2750rpm. Average highway cruising
speed is about 118km/h or 73mph.

 

EPA estimates for your car were 31 city/34 highway. Here's a partial
checklist:

I read your second post, and you might want to try reducing your speed a
bit. Try 110km/h (68mph). Also, go easy when taking off from a stop if
you tend to floor it.

Assuming 32psi is the Honda-specified pressure for your tires, are they
the correct size?

How are the spark plugs, wires, distributor cap and rotor? Are they OEM?

Is the weather becoming colder in your area? Cold temperatures will
greatly decrease your mileage.

 

How many miles are on this car?

I'm pretty sure your 90 Civic Wagon has the same engine
(code #D15B2) as my 91 Civic LX sedan. Your mileage
definitely seems low.

Try some of the tips at
http://home.earthlink.net/~honda.lioness/id11.html .

If the PCV valve has never been changed before, I'd pay
particular attention to it, per the site above. An update on
what you find would be welcome.

Next, I echo what High Tech Misfit said about the plugs,
wires, distributor cap, and rotor.

Then I'd start replacing/checking the other things I list at
the site above.

Do not coast on hills. Keep the car in gear. The engine
control system is actually less efficient, gas-wise, when
coasting.

See your owner's manual for the optimal shift points, though
what you're doing with shifting doesn't sound too far off.

 

I have a 1990 Honda Civic Wagon, 2WD, 5-speed manual transmission.

Now being a smart ass as I often am, the op has a European spec car and
is therefore probably using miles per gal (UK) and the EPA is using
mpg (US). (I did not convert back from his 9l/100km to check this
assumption)

A UK gal is about 1.2 US gals, so 31/1.2 = 25.9
and 34 / 1.2 = 28.3

so 25.9 to 26
and 28.3 to 29

seems pretty close to me.

 

Actually, the OP is in Canada and converted his litres/100km to miles per
U.S. gallons.

For his city mileage:

100km / 9.1 l
= (100 x 0.621) miles / (9.1 x 0.264) US gallons
= 62.1 miles / 2.40 US gallons
= 25.88 miles per US gallon

And the OP said 26mpg.

I'll leave the highway mileage conversion up to you.

 

I am in Ottawa, Canada, and it is a Japanese manufactured Civic (based
on the VIN). What makes you say it is a european spec car? My
conversions were also to US mpg.

Although the weather is becoming colder here, those figures are about
normal through the summer and the fall; as it gets further into winter
here, I usually see my mileage drop by an additional 1-2mpg. I keep the
car in gear all the time and never coast.

The car, I'm pretty sure, has a 1.5L D15B2 engine in it. The mileage on
the engine is about 265,000km or 164,663miles. The spark plugs, wires,
fuel filter, air pilter, pcv valve, distributor cap, and distributor
rotor were all changed at 205,000km; the spark plugs changed again
(NGKs) at 250,000km along with the oxygen sensor. Perhaps it's time to
start looking at some of those in more detail (if so, which?). The
coolant system just had a flush as well.

Thanks again for all of your advice.

 

that's not cause for concern.

is the sensor oem? aftermarket ones can be terrible. oem have fast
reaction times and produce much better performance.

other things to check:

1. check or replace the coolant sensor. if it's not sending accurate
information, the ecu will inject excess fuel. you get a similar result
if the coolant level is insufficient. to be sure of coolant, remove
the radiator cap, do NOT rely on the fluid level in the expansion bottle.

2. be certain the ignition system is ok. apart from ensuring all the
usual suspects are in good condition, i can report that performance and
therefore mileage can be substantially improved if an ailing ignition
condenser is replaced. also make sure the ignition timing is correct.

3. ensure the injection system is ok. run injector cleaner through the
system. a leaky injector can dump a lot of gas.

4. ensure the cam timing is correct. if the belt has jumped a tooth,
mileage and performance will degrade substantially although the motor
will still run. again in my experience, it's not uncommon for the belt
to be incorrectly tightened on replacement. it may not show as a
problem immediately, but it will after it jumps. with an ignition
timing light, observe the timing marks for a few moments [with the
service connector shorted as per the manual]. if the timing seems to be
fluttering back and forth a few degrees, that's a good indicator of a
loose timing belt. fix accordingly.

 

The coolant flush you mention below makes me suspicious. Did
you do it or a shop? (Just kinda curious on that one.) Check
the coolant level per the owner's manual, and do an air
purge of the system. This time of year, it's going to take a
while to get the radiator fan to come on twice during the
purge, like at least 35 minutes, so have a magazine. Post if
you want more info on what coolant to add, where to find a
procedure for the purge, etc. The cooling system supplies
coolant to some engine control components. If they're not
properly submerged, they'll malfunction and, ISTM, may
affect mileage.

I know you said the air filter looks okay, but it is due for
replacement about every 50k km, and it's cheap and easy to
replace, so I'd replace it.

Do you have a maintenance schedule for this car? It's in the
owner's manual but I also know some web sites that have it.

Were all the new parts you list above OEM?

Add a bottle of a fuel injector cleaner to the gas tank, per
the bottle's directions. I don't think that's critical; I
only started doing it a year or so ago with my 91 Civic, but
plenty here think it's a good practice.

Does the power (that is, acceleration) seem okay?

Well it's not good if it doesn't fix the problem. I
appreciate your thoroughness, as others learn from it. Keep
the group updated, and keep checking back.

 

Dangerous things assumptions - If you VIN starts JH it is a Japan built
car. For your interest it would have been made in Suzuka, and you can
even see a fuzzy image of the plant on Google earth !!!

I think it's at
34 51' 55" N, 136 31' 40" E

The Honda plant in Marysville is at
40 16' 47" N, 83 30' 47 W

Just cut and paste into the google earth search window.



but based on my current track record - who knows?

 

The coolant flush was done at a garage; I put a pellet of leak stop in
as well because I've had a pesky coolant leak that I haven't been able
to diagnose. I changed all the hoses, but the car still loses about
50ml of coolant per 100km of driving. It's small enough to be annoying
in that I'll have to check the coolant every fill up. After the flush
and changing the hoses, however, the leak seems to have diminished. The
rad is original, though, and missing a big chunk out of it.

I do have an owner's manual with recommended maintenance, and the new
parts are OEM. Power in the car seems fine with no hesitation and
healthy throttle response all the way to 6000rpm.

When I get a bit more time later this week I'm going to check the fuel
filter, air filter, and spark plug wires; they are about 60,000km old
now so that could be part of the problem. I'll also check out the
timing. The oxygen sensor and spark plugs are further down the list
seeing as the are only 15,000km old. I'll also look into getting a
bottle of injector cleaner.

I should mention I've owned the car since 250,000km and have always had
this kind of mileage. I've always felt the mileage should be much
better but haven't really gotten around to addressing it. In talking to
the previous owner, he mentioned that his best and worst experience for
the first 250,000km of the car was 9l/100km or 26mpg during the winter
in the city, and 6l/100km (39mpg) on highway trips in the summer.
Seeing as I'm doing 26/29 at the moment I'm pretty confident that there
is room for improvement. The problem is finding out how to get it.

I'll go through my records and see if I can post my mileage pattern.

 

That's less than 1/4 cup. I don't think losing this little
coolant between fillups is the problem, /unless/ the leakage
point also admits air into the system.

it.

As a result of this 'missing chunk' do you feel the radiator
may not be dumping enough heat to ambient? What does the
temperature gage read? My 91 Civic's is noticeably below the
halfway mark.

With this damage, can you even do an air purge of the
cooling system?

Plenty of folks have inquired here about replacing radiators
and where to buy new ones. Consider this at some point.

The wires are supposed to last way longer than the plugs,
fuel filter, or air filter. You'll see it in your
maintenance manual. People here post about wires being much
tougher than in the past, as well. No harm doing a
resistance check on them, though. They should be no more
than about 15k ohms each. Running the car in the dark with
the hood up is supposed to be a quick check as well. If you
don't see sparks coming from the wires, and the resistance
is sat, then they're likely fine.

As long as they're both OEM, I agree.

get it.

Lately I am wondering (based on my own experience and posts
here) whether an aged distributor coil knocks down mileage a
lot. That's not too expensive of a part (around $100 online
OEM), but the labor isn't difficult. If you know it's around
eight years old, then I would replace it as well. It's not
likely to last much longer.

Sounds like you realize this is going to take awhile. Hang
in there.