'90 Civic: Extremely sluggish low-end acceleration, poor fuel economy

A few more issues from my poor little car for anyone who can shed some
light...

My '90 5-spd Civic Ex has been bogging down at low RPMs since I bought
it last fall. When I accelerate from a dead stop I have to goose it to
about 2500rpm and then pop the clutch a bit to get it to take off as
quick as I think it should. Especially in an up-hill situation. (no AC)

If I drive it like other small manual 4-bangers I've owned (Corollas,
etc), it will literally take 5-10 secs to get to the point where I
think I should shift to 2nd. Gas pedal down half way or floored makes
no difference. Also, doesn't matter if the car is at temp or just
started. After 1st gear and I'm moving a bit, there's no problem. I
seem to remember reading about a potentiometer (maybe in the throttle?
can't remember the details) that, if the contacts were dirty, would
cause this type of thing. Maybe I'm just crazy and I dreamed this....

I'm also getting only about 15-18mpg in town and 20-23mpg hwy this
summer... seems incredibly low. Was getting the same last winter, but
wrote it off to cold weather. Spark plugs are about a year old, newish
air filter, and OEM O2 sensor's only 6 months old.

ECU's not throwing any codes.

-Back pressure too low/high? (bad catalytic converter?)
-Bad plug wires? (I'm sure they're not Honda OEM wires, but I think
they're only about a year old)
-Clogged EFI?
-Timing out of adjustment? I didn't fool with the dist. when I changed
the timing belt, mostly because I couldn't find a damn marking anywhere
on the crankshaft pully to save my life. Ran like a top after the belt
change, so I'm confident it's not a tooth off...

HELP!

Any advice would be greatly appreciated...

Regards,
-Bruce

 

That mileage is pathetic.

When's the last time you replaced the PCV valve? I replaced mine on my 91
Civic for the first time (way overdue) two years ago, and the mileage shot
up.

The plug wires?

Fuel filter?

Air filter?

All of these are easy to do, inexpensive, and could be a part of, if not
the, problem.

 

this is confusing - it's run bad since you got it? but it ran great
after you changed the belt, now runs bad again? if that's true, check
your timing belt, it's probably skipped a tooth.

 

Sorry.... that was kind of vague.

What I meant is that it runs great except for this 1st gear hesitation,
but that it's done it since day one. There was no difference
what-so-ever after the T-belt job. It starts on the first crank every
time, idles great and drives very smoothly (always has) except for the
sluggishness in 1st gear in low RPMs.

 

Do Honda plug wires make that much of a difference? What about brands
of plugs? The wires I have now are the most expensive ones at Autozone
and the plugs were about $2 each IIRC.

Air filter is only a few months old, doesn't look dirty at all.

I've heard the fuel filter is an easy job, but I've never done one
before. Where is it located and what does it look like? I guess if I
just buy one it will help me find it. I think my Haynes manual says
it's on the firewall, but it also states that the fuel pressure must be
released to do this, and it's pretty vague about that procedure.

Thanks

 

I checked the PCV valve a few weeks ago... I was told if the bead
inside is loose, it's ok. I blew some degreaser through it just to be
sure, but there is no moisture build-up in the crank case. I guess for
a $3 part I might as well get a new one, but I don't think it's the
problem.

Do Honda plug wires make that much of a difference? What about brands
of plugs? The wires I have now are the most expensive ones at Autozone
and the plugs were about $2 each IIRC.


Air filter is only a few months old, doesn't look dirty at all.


I've heard the fuel filter is an easy job, but I've never done one
before. Where is it located and what does it look like? I guess if I
just buy one it will help me find it. I think my Haynes manual says
it's on the firewall, but it also states that the fuel pressure must be

released to do this, and it's pretty vague about that procedure.


Thanks

 

I don't buy this. There's a spring in there and it will lose its optimum
effectiveness over time, despite the little test one can do to hear the bead
operate the valve. The valve is a control valve, meaning it often operates
somewhere between fully open and fully shut, so the spring's integrity
should be vital.

Particularly if it's the original PCV valve, I would replace it. Just one
easy thing to eliminate.

Now I fully remove my Civic's PCV valve once a year and spray PB Blaster
into it.

Buy the OEM PCV valve for around $20 at your dealer's. Word on the street is
that the non-OEM versions are not good.

My understanding is yes. Buy the OEM plug wires. (I am frugal, by the way,
but over the years I've learned my lesson on certain Honda engine parts and
find the extra bucks laid out now saves me trouble later.)

Buy what the owner's manual recommends. My 91 Civic manual lists the exact
plugs for three different manufacturers (NGK, ND, and Champion). I don't
think platinum makes any noticeable difference, so don't let the salesperson
at Autozone or wherever talk you into the platinum version unless you think
it's cost-effective and/or improves performance.

I think NGK is popular and a safe bet among people here.

Lose these.

Sounds good.

That's where it is on my 1991 Civic.

Autozone should have a free online repair guide for your Civic that matches
Chilton's. The Chilton manuals are better than Haynes, in my experience.

Or go to http://www.honda.co.uk/owner/ConcertoManual/index.html. Go to the
"Fuel and Emissions" sections, and click on "fuel filter." There's a drawing
there that may help. The Concerto engine is very similar, if not identical,
to the early 1990s Civic engines. The torque specs vary, though, so you
should go to Autozone or get a Chilton's to get the exact torque specs for
your fuel filter.

Many years ago during the first time I replaced the filter, I found getting
the bolts loose a little tricky. I had to find ways to brace wrenches etc. I
also didn't have the best wrenches for the job. Now I do. Having done this
four or five times, it's now a piece of cake.

It's not hard nor particularly dangerous to release the fuel pressure. One
just slowly loosens what is called the service bolt on the top of the
filter, holding a rag around it, so some gasoline leaks out and relieves
pressure.

As I trust you can imagine, these are all regular maintenance items, so by
doing them, you haven't really wasted money, and you've narrowed down what's
behind your Civic's problems.

 

It's not. And unless it's aftermarket, there's no "bead", just a plunger
and spring.

 

I fianlly replaced my original a few weeks ago. It had 14 years and 248,000
miles on it. Didn't make a bit of difference to gas consumption or engine
running.

New FAQ page on that saga:
http://www.tegger.com/hondafaq/pcv-replace/index.html

Pics are part-way down.

 

automatic or stick?

if automatic, ensure the timing is correct, clean out the egr valve and
replace the thermostat.

 

By your own admission, you totally baby your car.

Needs work.

You and I continue to disagree on this. A guzillion web sites back up my
(along with like every other regular's) position on this.

 

That is my point. Cars that are not taken care of are the ones that suffer
from this.

And every working mechanic I have ever spoken to about this says exactly
what I put up on that page.

 

5-spd...I've been thinking about checking the timing for a while, but
last time I had the engine torn apart I studied the crank pulley for a
good 10 minutes in fairly good light looking for a timing mark and
found nothing.

Is it a paint mark? or a metal nub? I cleaned it off with some
degreaser when I changed my timing belt and still couldn't find any
mark.

What gives? Maybe this is just related to late-80s/early-90s Civics...
My 88 Toyota PU has a very obvious orange mark on the pulley and it's
really easy to see.

 

if the pulley is rusted, it's not so easy to see, but it's a tiny cut
between the alternator & a/c bands. should be painted too. you can't
see it from the side - you have to look down the gap between motor &
body near the l/h motor mount.

 

Well, I'm going to change the PCV just because I kind of doubt the
previous owner put in an OEM Valve, IF he changed it at all. One less
thing that could be causing my mileage problems, and it probably needs
done anyway.

But, I'd also like to check the timing... any advice on finding the
timing mark on the crank pulley? I assume it's just a little dab of
paint and that I'll have to put some white-out on it to make it visible
with the timing light, but I can't see ANY mark on the pulley. Nada.

And I need to short the contacts under the kick plate in the passenger
compartment to disable the auto-timing adjustment too, right? That
sounds easy enough, but if I can't find the mark on the pulley it's a
moot point.

Thanks guys.
-Bruce

 

Gotcha... should have considered that as I know you have to look down
and line up those two little pointy things on the timing belt cover to
check it. A little white-out will help me see it w/ the timing light
while the pulley's turning.

Thanks

 

I just tried two experiments on my own 1991 Integra just now.

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

Firstly, I tried plugging the PCV hose shut. The idle dropped momentarily,
then climbed smoothly back up to 750 and remained there.

When I let go of the hose, the idle surged briefly, then settled back to
750rpm. As expected, the engine management system was adjusting air flow to
achieve correct idle speed.

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

Secondly, with the car fully warm, I unplugged the PCV valve hose at the
pipe where it enters the intake manifold, so the PCV intake was completely
open as a massive air leak into the intake downstream from throttle plate.

The idle dropped momentarily, then began smoothly surging between 1,000rpm
and 2,500 rpm. As expected, the engine management system, crude as it is,
was attempting to adjust the mixture to be correct. The air leak being too
great, however, it was unsuccessful in doing so.

(Interestingly, air flow from the PCV valve itself stopped dead, suggesting
that ambient air pressure was keeping the valve shut. IOW, crankcase
pressure was lower than ambient.)

I then plugged the PCV intake pipe with my thumb, mimicking a plugged PCV
valve. The idle returned to a smooth 750rpm and stayed there.

I discovered that I could uncover up to a quarter of the PCV intake pipe
before the idle began surging again, the severity of the surging directly
related to the amount of exposed intake pipe.

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

Conclusion: Cars with engine management systems do not suffer noticeable
problems from a plugged or stuck-open PCV valve unless an extremely unusual
situation is present.

History:
I once had a 1975 Toyota Corolla with a carburetor and no feedback system.
This car would not idle at all with the PCV valve removed. Unlike the
Integras's feedback system, the carburetor was unable to compensate for the
excess air. I discovered this quite by accident when an aftermarket PCV
valve came apart on me.

 

Like Jim said, it is hard to see. You should go at it from the top, and with
a flashlight, using the directions he gave.

That degreaser you applied may have helped shorten the life of the pulley's
timing paint marks. The marks are mechanically etched into the pulley,
though, so they should still be somewhat visible.

You do realize it's four marks, all within about 10 degrees (too lazy to
think about the exact degrees apart they are), right?

There was a photo online of the c. 90 Civic's timing marks at a certain site
that I'm trying to pull up now. My Chilton's has a drawing and photo, so
Autzone.com and probably the UK site should have at least the drawings, too,
under "ignition timing." I'll post a link if I find it.

Yes.

 

FWIW, go to http://www.honda.co.uk/owner/ConcertoManual/index.html , and
click on Engine Tune-Up, then "Ignition Timing... " at the bottom for some
drawings of the engine and its timing marks. Check out the CRX manual's
drawings, too, at the UK site. They are slightly different.

www.autozone.com has the drawings and photo (under its free repair guides;
"engine performance and tune-up"; "ignition timing") too. I have been having
error messages when I accessing some of Autozone's sites from home, but I
found that repeatedly refreshing usually clears this up.

Ignore the UK site's steps on this. The c. 1990 Concerto and CRX have a
different set up for disabling the automatic ignition timing adjustment.

 

indeed, but don't make the mark too big - even 2 degrees out made my 91
crx hesitate.