Efficiency: 90-93 Accord 2.2L 4cyl

Hi Folks,

In January my trusty Accord has changed jobs - from off-peak runs to the
store and weekend trips, it is now my daily commuter. Work is just under 20
miles away - with 16 miles of expressway at one end, and residential
streets on the other end. I've been keeping track of mileage by the tank -
about 14 gallons from full to the light coming on.

Anyway, I've been getting around 24mpg. One tank I drove more or less as
gently as I could, upshifted early, cut my speed a bit etc. That tank I got
26.5mpg. It's better, but honestly it's not enough of a difference for me
all by itself.

Question 1 is for folks who have the same car: how does your mileage stack
up against mine?

Question 2 regards improvement: I'd be interested in minor modifications
(or maintenance items I've overlooked) that will improve the efficiency.
Decreasing cruising speed and accelerating more slowly are of course always
options, but I'm interested in something beyond that though. One variable
here is that the weather is getting warmer, so that will change my
efficiency somewhat by itself.


Some things I already know to do or have done:
o tune up items (done in Feb - included air filter, plugs, rotor/cap, valve
clearance)
o tire pressure (checked, ok)
o running temp (I believe it's OK, predictable gauge behavior right to
center line, and ample heater performance)

Any suggestions?

Arthur
Approaching 150k miles, 91 Accord LX sedan manual (2.2l F22A1)

--

P.S. Has anyone actually done what Ricky suggested below? I have a spare of
the check valve of which he speaks, I'm guessing the air pressure drop
across it provides the drop in fuel pressure he mentions.
But it seems to me that provided the system is still running closed loop,
the ECU will modify the injection timing to servo the O2 reading back where
it should be. I'm not interested in running open loop!

The excerpt is from a related thread for these 90-93 Accords:

 

I'd make sure that you aren't shifting TOO early. Lugging an engine will
give you worse fuel economy, not better. Also, when you change the plugs,
use NGK or ND. And if you need to change the cap, rotor and wires use the
Honda parts. (they are cheaper than the after market stuff and there won't
be any question about too high of resistance). While you are adjusting the
valves, pull the timing inspection plug out of the tranny and make sure the
timing belt hasn't slipped a tooth. I'd also set the timing and base idle
speed. Cleaning the throttle body couldn't hurt either. Also having the
injectors cleaned, either on the car or off could make a large difference in
mileage. I would think that car should get close to 30 MPG with a lot of
highway driving.

 

I drive a 92 Accord, 2.2L, 4 CYL, AT, with 153000 miles as my daily drive,
about 15-20 miles a day generally. I get about 25 mpg city and about 30 mpg
highway when i go out of town.
With a MT, you are getting less mileage than my AT, so something's surely
wrong. I don't use any of those after-market STP, etc all-in-one system or
fuel-injector cleaners.
I use NGK plugs, if that helps.

 

I have a '91 Accord automatic with 215K miles and it gets about the same gas
mileage as it did when it was new; city 20-24mpg, depending on the season
and type of driving, to 29-30 on the highway (steady 70 mph). You city
driving component is where you are taking the hit. If you are getting 20
mpg in the city and 29 on the highway, using your percentages that's
5+21.75=26.75. Not much different from what you report. How agressive do
you drive, how up&down is your highway component? spending a lot of time at
stops/lights. Take the car for a 100+ mile highway trip and see how it
does. If it's in good shape and tune, you should get 30ish for an automatic
and 32+ for a manual tranny at 65-70 mph.

Lugging will hurt your mpg's. A good shift range is 3000-4000 rpm's. You
won't lead the pack, but it will get you decent mpg's and help the longevity
of the engine (think like the airplane mechanics do: wear is directly
proportional to engine speed).

I have used ND, NGK, Bosch and Autolite platinum plugs with all giving about
the same results. The last set went 80-90K miles with no big change in fuel
economy when they were changed. Regular plugs aren't rocket science.

Is your air filter clean?

Injectors can be cleaned up a bit by running a few tanks of premium through
the engine. The increased octane won't make any difference to your engine,
but premium fuels generally have better additive packages than regular. One
of the symptoms of dirty injectors is rough idle and or poor acceleration.

Try inflating your tires to 35 psi if you haven't already done so. The
honda spec for air pressure is a compromise for ride quality.

A dirty or clogged egr will affect mileage (and idle) as well as a faulty O2
sensor (which will trip the check engine light--but if it's starting to fail
may not have done so yet. Many people replace the O2 sensor after 100K
miles, I still have the original--go figure.

Gas mileage can change substantially with the seasons. If you live in a epa
clean air non-compliance area (any major city or downwind of one) the winter
fuel blends give lower mileage than the summer blend. Ethanol blends, 10%
or so alcohol--see major city comment, will also cut mileage slightly.

Use 5W30 oil all year, if you aren't already doing so.

Mileage is a sum of the parts thing. An mpg here another one there and soon
you'll be up to 28-30+.

Good Luck.
PS

 

Have you ever changed out the PCV valve?

It's under $20 at most places. I changed mine out on my 91 Civic for the first
time at 140k miles. My mileage went up 15% to 20%.

 

I have a 1993 Accord LX automatic Canadian model, which is similar to the
American base DX model. The best I have gotten on the highway is 36mpg, but
I usually average 32-34mpg. This is with the cruise control engaged.

 

Hi,
Apolgise for my question (i'm French...)

What is PCV valve for?..

Thanks.

Philippe

 

Positive Crankcase Ventilation.
Unburned hydrocarbons that "blow by" the piston rings can be found in the
crankcase of older cars. The PCV valve draws the vapors into the engine to
burn them.
At one time there was a thing called a "road draft tube". The blow by was
vented under the car so that the fumes wouldn't bother the occupants, but
unburned hydrocarbons are a gross contributor to visible air pollution.

 

Both you and PS mentioned shifting too early. It certainly could be true
since the Owner's Manual lists "shift speeds for maximum efficiency", and
if you follow it you end up shifting from about 3k to 2k each time. I'll
try a tank or two shifting at their points.

For the record though, I'm not lugging it. I'm not interested in excessive
detonation pressure/fractured crowns and/or premature clutch wear!

....

I've been shifting earlier for two reasons: the first is the fairly well
known BMW report done some time back (that was a bit a of a surprise to
some folks) that said, as I understand it, without lugging it, maximum
efficiency is attained by shifting as early as possible. Previous to this,
apparently folks had thought the best thing to do was to wind it way up.
This updated philosophy seemed to have been adopted in the shift schedule
of my old 88 Camry - an efficiency aware car.

The second reason is that for me, shifting early is a way to keep the
responsiveness down a bit. This makes it less tempting to give it more gas
(since the response isn't very exciting anyway). Yeah, I should ease off,
but DAMN - I love the 3rd gear in this car all the way through the rpm
range, and 2nd gear at about 4k is pretty fun too.

So anyway, even though shifting early has improved the situation somewhat,
I'll try the shift points in the manual.

Thanks,
Arthur

 

OK, thanks for the data. It sounds like I have you beat, or at least we're
real close. I'm getting 25-27 for my mix of city/highway commute, and
though I didn't mention it I get more like 31-32 on the highway. For
sustained travel at 75mph cross country in the summer (2000 miles back in
1996) I pulled closer to 35 (it was long ago, and that's only from memory)

You might (still) be right that something's wrong though. I also don't use
aftermarket stuff. Plugs are new at last tuneup - I guess I can ask what
they used (but I'm not sure I'm sold on the spark-plug effect!)


------------------------------------

This also sounds in line with what I'm getting. If I'm in situations where
the cruise control is usable, I get 31-34 or so. My best might be 35, again
from distant memory (we have a nicer car for long trips now...)

 

I have a '91 Accord automatic with 215K miles and it gets about the same gas

I assume you've got the LX or DX (EX has slightly more performance but
worse efficiency). I think I'm in line with your estimates...maybe a bit
better actually.

Yeah, other folks mentioned this too. This is certainly something I will try.

As an aside: The airplane guys I talk to say it's hours on the engine (I
assume it's still horsepower-hours, but in a prop plane you might know
enough about average, or RMS, power output to just count hours).

On the plugs: yeah, I'm not real convinced that plugs are going to do
anything interesting here (unless they have worn electrodes/poor gap etc,
but mine are good).
Both were done in Feb.

It's possible I have a shitty spray pattern on the injectors. Premium's not
gonna fix it though. I've even run a bottle (maybe two?) of "Fuel Injector
Cleaner" through with no discernible change. Honestly, I'll probably look
for other symptoms before I start suspecting them though. Now I have to go
read up on the symptoms of fuel injector clogging!

Yep, that's not a bad suggestion. Certainly running with them at 30psi
would sap efficiency.
My only concern with running the tires that high is that you start to
sacrifice grip etc.

EGR troubles will throw a code (unless some ports are blocked and some
aren't...a known issue for our vintage car). I had my ports reamed last
year on a hunch, and I _think_ I have more pickup now, but hard to say for
sure.

O2 sensor is an interesting one. I don't have any reason to think it's not
working right. Emissions are excellent (even with the new dynomometer
acceleration profile testing they do here in Mass now.)

Not to mention that when the engine is in warm up mode, it REALLY sucks
down the fuel. In New England when it's consistently 15F or lower, I have
gotten as low as 17MPG for a tank! Anyway, there's not much I can do about
the gasoline formulation...

Well, it's Mobil 1 so it's 5w-40 or whatever.

Thanks for the tips,
Arthur

 

I haven't. I got the car at 100k, so I don't know that it's original.
However, I have checked it for function, and it was fine. Now, the grommet
it plugs in to at the valve cover MIGHT be worn out.

Do you know what the cause-effect is here for loss of efficiency? Would a
leak at the grommet (essentially a leak in the crank case air space) cause it?

-Arthur

 

I have a 93 Accord LX 5 speed with the F22A1. It has 305k miles on
it, and still running strong. I average about 28-29mpg with a mix of
highway and city miles. I am also a bit of a ledfoot. Hope this
helps!

 

I've been thinking about the shift point that I recommended. So, yesterday I
paid attention to whatpoint I was typically shifting at (I drive by
feel/sound and let up on the gas to force the engine to upshift) I think
that you can probably drop it some. The 2.2 probably is strong enough to
easily handle things down to 2200ish rpm (maybe even lower)--the Honda
manual is right.

Try to drive at a steady speed, the operative word being steady, on the
highway--even if you are not shifting much. The ups and downs can be an
mpg. I try to drive about 1-2 mph slower than traffic and let the others
pass me. That way I don't have to speed up/slow down to get around traffic.
It's less stressful, too. Here in Illinois we have tollways and they back
things up enough that I catch up to all the cars that passed me at the next
tollbooth! Stops, light, exits, etc have more affect on the travel time
than getting back up to 70 asap. Do whatever you can to always be moving,
e.g don't rush to stop lights.

 

Let me see if I undrestand you: you currently ARE getting 31-32 on the
highway. I think your car is probably in decent tune, or close to it and
your driving habits may have more to do with the current mileage than
anything mechanical (see my other post).

The 35 on the long road trip was due to less stops between fill ups and a
steady pace. On long trips, if I go 175-250 between stops (and fill ups) I
pick up an mpg.

 

91 4dr lx, 215k mi

re planes, you're right it is hours on the engines, but they're similar to
OTR diesels, they run at a fairly narrow rpm range for long periods of time
(peaking for short periods during take off and landing). Hours & # of trips
is the easiest way to determine the maintenance intervals. I'll bet that
the maintenance intervals for an airplane engine are shorter if the average
cruising speed is higher.

Wear is all about friction, so, hypothetically, in your car if you drive
1,000 or 10K or whatever at 2500 rpm average, the wear will be less than if
your drove it at 5000 rpm average. It will have experienced 1/2 the cycles,
obviously. Sure lower RPM gets you better mileage, but most people pay no
attention to the longevity issue. Slow it down and the engine lasts longer.
This factor is no doubt built into the oil change monitors on newer
vehicles.

A spark plug can last 80-100+K miles with a good electronic ignition. Just
check the gap every 30-40K miles.

Given the highway mileage that you post elsewhere, I don't think you
injectors are clogged. They do wear, but I can't tell you exactly how to
trouble shoot that--probably excessive fuel consumption, poor performance,
rough idle/acceleration. If you haven't abused your car, I don't think you
have an injector problem.

Don't worry about grip changes, tire manufacturers recommend to increase the
pressure for sustained driving at higher speeds. Underinflated tires
actually increase pressure more than a properly inflated tire. Just don't
exceed the cold psi recommendation on the tire. Adjust for seasons, and
watch the wear pattern: excessive wear in the middle means over inflation.
"Green" tires are 50-60 psi standard!

I've run Mobil 1 for nearly the entire life of the car, so far. Change it
2ce year regardless of mileage (7-10K/change), engine is in great shape.
Don't burn any more oil than I did when it was 3 yrs old. Try 5W30, while
the pour points are only slightly different, if I understand oil viscosities
at all, the 5W30 will lubricate just fine in the summer, better (although
synthetics are better than conventional any time of the year) in the winter
and will have less internal resistance. This is the only reason why the car
manufacturers are going to 0W20 or whatever it is. They can pick up
..25-0.75 mpg just with the switch. Transmission design and fluids have been
changed to inprove fuel efficiency in the same manner. (This is one of the
ways that the mfr's have maintained or slightly increased fuel economy while
greatly increasing the engine output and or size? As I said elsewhere it's
a game of summing small incremental improvements)

Not much you can do about cold weather, save maybe garage the car and drive
it (don't sit at lights--the key is to get the oil up to temp).

 

PCVs are cheap, replace it. Or if you are a true tightwad, flush it with
wd40 and blow through it--it will allow one way pressure;it's just an
inexpensive check valve.

 

I have a '93 LX AT with 131k miles. I drive with an extreme lead foot
and I get 20.5 MPG in city driving. When I made a conscious effort to
drive like a grandmother, I got 26MPH in city driving. I drive with the
air conditioning on 99% of the time, summer or winter.

Andrew

 

Yes, I think you've got it. This is what I was trying to say in the
original post. That is: I don't have reason to believe that the car is out
of tune (although I did ask for others' data to confirm), but I'm not
interesting in severely altering my driving habits, or, if I do, I want
more than a couple mpg increase to show for it.

So, what I *am* interested in is modifications that will improve the
situation (changing drivers is out, and so are major modifications like
engine swap etc.)

-Arthur

 

Right. It is clean. Next time I'm at the junkyard I'll get the grommet though.