91 Civic intermittent problems -Symptoms update

This question is for a 91 Civic HB with 190K.
The first symptoms were engine misfiring and car jerking when I hit the gas,
occasionally. Then I started having intermittent starting problems. Engine
turns but won't start. It happened when the car was cold or warm. Dash
lights work and I can hear the fuel pump when I turn on the key. Couple of
hours of wait solved the problem.
I pulled out the spark plugs. Considering the mileage of my car, there was
some oil on the plugs. Oil consumption is less than a quart per 1000 miles.
I replaced the spark plugs, oil, air filter, PCV valve and problems seemed
to go away for a while (2 months). Then same things started to happen again
recently, replacing the plugs won't help anymore. Distributor cap, rotor and
plug wires are ok. No ECU codes present. Ignition coil resistances are
within specifications.
I am mainly considering three possibilities: Oil fouling of spark plugs,
ignition coil/igniter/distributor failing or faulty fuel injectors.
I am getting more than 30 mpg, no over heating and engine is idling
smoothly.
Any help is greatly appreciated.

 

--------------------
Sean,
Don't confuse liquid oil on the threads of the plugs with burnt-on oil
on the electrodes. The former is just the o-ring seals inside the valve
cover where it mates with the head. Minor problem.

Did you ever run some gasohol or injector cleaner thru the engine? When
it finally starts, does it 'chug' and / or blow smoke for the first ten
seconds?

'Curly'

 

Actually the oil was at the tip of the spark plug, around the center
electrode.
I use fuel injector cleaners quite often. I haven't noticed excessive smoke
from the tail pipe. Do you thing the cleaners have something to do with it?

 

Just a guess, but do you think your exhaust is free flowing? Maybe your
catalytic converter is plugged? It sounds like you did a lot of
replacing basic maintenance parts, but I didn't see the fuel filter listed.

Here's a link to the UK 1988-1991 Honda CRX manual.

http://www.honda.co.uk/owner/CRXManual/index.html

It is all Acrobat PDF files. I think it should help some. It seems
fairly similair to my USA 1991 Honda Civic manual.


Mark

 

I have replaced the fuel filter 2 years ago, I guess it is time to replace
it again.
Not sure about the exhaust or the catalytic converter. Any idea how to check
them?

 

Sean,

I noticed after my previous post that the UK CRX has a DOHC engine, so
that manual may not apply as much as I hoped. I think I had used it for
suspension, so it worked for me. I think Caroline (a new screen name
now?) uses the UK Concerto manual to compare to the USA 1988-1991 Civic.

I doubt your fuel filter would be the problem if its only 2 yrs. old. I
have heard that the pipe that connects the cat to the exhasut manifold
has 2 layers, or sort of a pipe within a pipe, and that the inner pipe
can collapse. Try whacking around it with a wrench or whatever and see
if it sounds solid. I think cats can plug too, so maybe if you whack
that a bit and it sounds like its full of loose material it may be worth
unbolting and inspecting.

Maybe Jim Beam, motsco, Tegger or someone more knowledegable will reply
after some time, but I haven't had your problem specifically. I will say
that when I got my 91 Civic it ran fine, but after 10k miles it didn't
run so well and I eventually found the timing belt off a tooth. If you
can find a timing light, it may be worth checking your ignition timing.
If it is WAY off, your T-belt may be installed incorrectly.

Mark

 

If you've investigated the EFI main relay and ignition switch possibilities
and ruled those out, it sounds suspiciously like the coil breaking down
under load. Static resistance tests won't find failure under load.

You may be able to get a coil cheap at a wreckers to try out.

 

in addition to what those above have said, double check your plug leads,
distributor cap & rotor arm too. they're relatively cheap to replace
and bad ones can sometimes lead to problems like you describe. when the
mix in the cylinder changes, ie. when you put your foot down, the
voltage necessary to spark the mixture changes [voltage decreases with
increasing throttle iirc]. this means that if the plug is trying to
spark at a lower voltage than say a defective plug lead will conduct at,
you can experience a misfire. likewise, if you have a cracked
distributor cap or rotor arm, warmup can cause condensation & conduction
of the spark to earth. problem goes away when the engine cools again.
frustrating!

check the plug leads with a resistance meter, or just replace if they're
old. examine the inside of the distributor cap under strong light for
any signs of cracking or spark tracking. same for the rotor arm. both
these parts should be replaced periodically anyhow.

 

Can you describe what happens in the engine when you are going up a hill and
floor the accelerator? If you are on a high gear, speed won't increase. What
happens to the extra gas?
Seems like my engine misfires when you increase the throttle but speed
doesn't change, rather than smooth acceleration.

--
Secin Guncavdi, Ph.D.
Electrical and Computer Engineering
University of Wisconsin

 

Can you describe what happens in the engine when you are going up a hill and
floor the accelerator? If you are on a high gear, speed won't increase. What
happens to the extra gas?
Seems like my engine misfires when you increase the throttle but speed
doesn't change, rather than smooth acceleration.

 

if you're not in the right rev range, you're not getting a good charge
into the cylinders, so the ability to produce more power is limited.

goes out the tail pipe.

that's not necessarily a sparking problem. you sure the injectors don't
need cleaning?

regarding the possibilities for incomplete ignition, let me say i'm real
rusty on this stuff - it's been a long time since i did the theory so
feel free to laugh if i get it wrong.

iirc, the ability of the air in the plugs spark gap to break down &
conduct electricity depends on the density of the air and the size of
the gap. inside the cylinder and subject to the engine's compression &
changing fuel charge, gas density varies, and so does the voltage
necessary to spark it. if there's cracking in the distributor cap, or
bad plug leads, the voltage necessary to spark the plug may exceed an
alternative leak to earth at some gas densities & not others, hence
erratic ignition behavior.