Honda Car Forum

Dear All,

Recently, my friend's 1.5L Civic EK had slight hesitation on acceralation,
some consumption of engine oil and decrease in mileage (increase gasoline
consumption). I had the air-cleaner and spark plug for him. The air-cleaner
looks satisfactory but the colour of the spark plugs are a bit strange -- it
is purple around the point gap. Any idea of the problem and what is causing
the purple colour. Thanks in advance.

Perpetuus

For the oil consumption and decrease in mileage, I'd replace the PCV valve
first. A clogged or malfunctioning PCV valve can cause (1) an increase in
pressure in the crankcase, forcing oil past seals it ordinarily wouldn't get
past. and (2) the ECU to be fooled so that it causes the engine's combustion to
run rich.

See how it runs then. If the slight hesitation is still present, I'd start with
general tuneup type things, starting with a new fuel filter and new plugs. If
these don't fix the problem, then try also new ignition wires, distributor cap,
and maybe distributor rotor. Lastly, check the timing, adjusting the distributor
housing as necessary.

I was curious about your purple spark plugs and so googled for {"spark plug"
purple} got a few hits right away. E.g.:

"Red to purple deposits on one side of the core nose are an indication of a fuel
additive. While many of these deposits are non-conductive and do not contribute
to lack of performance, some fuel additives contain octane boosters that leave
conductive deposits on the core nose. Care should be taken to select fuel
additives which are compatible with ignition systems and do not contain
conductive materials such as octane boosters."
http://www.nightrider.com/biketech/spkplghnbook.htm

http://www.circletrack.com/techarticles/71898/ said this is a symptom of
overheating (but why?)

Only use a brand of spark plugs recommended by the owner's manual.

The year and mileage on a vehicle is often helpful to discussion here. Maybe you
could provide these in your next post. :-)

"Zebra" <t_perpetuus@hotmial.com> wrote
> Recently, my friend's 1.5L Civic EK had slight hesitation on acceralation,
> some consumption of engine oil and decrease in mileage (increase gasoline
> consumption). I had the air-cleaner and spark plug for him. The air-cleaner
> looks satisfactory but the colour of the spark plugs are a bit strange -- it
> is purple around the point gap. Any idea of the problem and what is causing
> the purple colour. Thanks in advance.

Caroline,

First of all, thanks a lot for the information. They are very useful.
Second, my friend's civic is a 1997 car with approximately 70000+ km. I have
suggested him to change the air filter and spark plugs first. Now, I need to
check with him whether he had add anything into his gasoline. Thanks.

Perpetuus

On Mon, 02 Aug 2004 15:54:07 GMT, "Caroline"
<caroline10027remove@earthlink.net> wrote:

>For the oil consumption and decrease in mileage, I'd replace the PCV valve
>first. A clogged or malfunctioning PCV valve can cause (1) an increase in
>pressure in the crankcase, forcing oil past seals it ordinarily wouldn't get
>past. and (2) the ECU to be fooled so that it causes the engine's combustion to
>run rich.

1. The crankcase is not a sealed system. A clogged PCV will only
result in NO POSITIVE crankcase ventilation. The blowby gases will be
vented out to the cars intake (before the TB). - No increased
pressure in the crankcase.

2. The ECU may be able to trim the fuel at part throttle using the O2
sensor. I have no idead how much air the PCV flows, so the amount of
fuel trimming available may not be enough. Ofcourse whenever the O2
sensor output is not used by the ECU, you are right, the engine will
run richer.

Bye,
Leon

"Leon" <Curb_Weight_69@hotmail.com> wrote in message
news:q992h01nvm00oqhudc0mj2trm18aau8ho1@4ax.com...
> On Mon, 02 Aug 2004 15:54:07 GMT, "Caroline"
> <caroline10027remove@earthlink.net> wrote:
>
> >For the oil consumption and decrease in mileage, I'd replace the PCV
valve
> >first. A clogged or malfunctioning PCV valve can cause (1) an increase in
> >pressure in the crankcase, forcing oil past seals it ordinarily wouldn't
get
> >past. and (2) the ECU to be fooled so that it causes the engine's
combustion to
> >run rich.
>
> 1. The crankcase is not a sealed system. A clogged PCV will only
> result in NO POSITIVE crankcase ventilation. The blowby gases will be
> vented out to the cars intake (before the TB).

Interesting. Through what aperature?

"Leon" <Curb_Weight_69@hotmail.com> wrote
> <caroline10027remove@earthlink.net> wrote:
>
> >For the oil consumption and decrease in mileage, I'd replace the PCV valve
> >first. A clogged or malfunctioning PCV valve can cause (1) an increase in
> >pressure in the crankcase, forcing oil past seals it ordinarily wouldn't get
> >past. and (2) the ECU to be fooled so that it causes the engine's combustion
to
> >run rich.
>
> 1. The crankcase is not a sealed system.

I don't know what you mean. For one, I call the oil pan gasket a seal that may
be compromised because of excessive crankcase pressure.

> A clogged PCV will only
> result in NO POSITIVE crankcase ventilation. The blowby gases will be
> vented out to the cars intake (before the TB). - No increased
> pressure in the crankcase.

Numerous authorities beg to differ. E.g.

"A restricted PCV valve can cause this excess pressure to find new avenues to
vent, and an oil gasket or seal is usually "blown out" to let this pressure
escape." http://www.trustmymechanic.com/valve_cover_leak.htm

"Engine is using more oil than normal. Oil puddles under the car when parked...
The PCV system is not working properly: Replace PCV valve."
http://autorepair.about.com/cs/troub...a/bl303a_3.htm

These are merely the very first two hits of a Google search for {"PCV Valve"
"oil leak"}.

And here's the Car Talk guys on the subject:
-----
RAY: Blow-by occurs when combustion gasses slip by old, worn-out piston rings
and end up in the crankcase, where they don't belong. Actually, a small amount
of blow-by is normal and is easily expunged by the crankcase ventilation system.
But on old heaps (i.e., yours), worn-out rings can let so much stuff into the
crankcase that the ventilation system just can't handle it.

TOM: So the pressure in the crankcase builds up until gasses and oil try to
escape any way they can. And we often see air-filter housings full of oil, seals
blown out or leaking, and the occasional dribbling dipstick.

RAY: The solution is an engine rebuild, which would include a ring job. But
before you consider that route, or ditch the truck, I've got two other things
for you to try.

TOM: If you've lived a really good, clean life, your problem might just be a
plugged crankcase ventilation system. So have your mechanic check out your PCV
valve and the hose it's attached to. ...
-----
http://lang.motorway.com/home/articles/qandaoilydip.asp

The fact is that a clogged PCV valve results in one less possible avenue through
which blowby gases may escape. The average pressure in the crankcase of course
will tend to be higher as a result.

Also, you might want to consider that how serious oil leakage may be when a PCV
valve is clogged will likely vary from one car design to another.

> 2. The ECU may be able to trim the fuel at part throttle using the O2
> sensor. I have no idead how much air the PCV flows, so the amount of
> fuel trimming available may not be enough. Ofcourse whenever the O2
> sensor output is not used by the ECU, you are right, the engine will
> run richer.

According to my reading, it's very ambiguous as to whether a malfunctioning PCV
valve may affect correct combustion in open loop, closed loop, or both.

It may depend on the specific car design. There is quite a lot of minor
variation from one PCV system to another.

On Wed, 04 Aug 2004 21:08:07 +0300, Leon <Curb_Weight_69@hotmail.com>
wrote:

>On Mon, 02 Aug 2004 15:54:07 GMT, "Caroline"
><caroline10027remove@earthlink.net> wrote:
>
>>For the oil consumption and decrease in mileage, I'd replace the PCV valve
>>first. A clogged or malfunctioning PCV valve can cause (1) an increase in
>>pressure in the crankcase, forcing oil past seals it ordinarily wouldn't get
>>past. and (2) the ECU to be fooled so that it causes the engine's combustion to
>>run rich.
>
>1. The crankcase is not a sealed system. A clogged PCV will only
>result in NO POSITIVE crankcase ventilation. The blowby gases will be
>vented out to the cars intake (before the TB). - No increased
>pressure in the crankcase.

It's not sealed but as discussed umpteen times here recently a PCV valve,
as implemented by Honda, is a metered air leak through the crankcase. The
blow-by gases plus the leaked air is *sucked* into the inlet manifold
through the valve, therefore there must be a reduced pressure vs. no PCV
valve. If the valve is clogged, yes the blow-by gases will pass through
the breather tube, to upstream of the throttle valve, but there is nothing
sucking them there... i.e. higher pressures in the crankcase.... which are
pulsed in all but a few rare V8 configs.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

"Steve Bigelow" <stevebigelowXXX@rogers.com> wrote
> "Leon" <Curb_Weight_69@hotmail.com> wrote
> > <caroline10027remove@earthlink.net> wrote:
> >
> > >For the oil consumption and decrease in mileage, I'd replace the PCV
> valve
> > >first. A clogged or malfunctioning PCV valve can cause (1) an increase in
> > >pressure in the crankcase, forcing oil past seals it ordinarily wouldn't
> get
> > >past. and (2) the ECU to be fooled so that it causes the engine's
> combustion to
> > >run rich.
> >
> > 1. The crankcase is not a sealed system. A clogged PCV will only
> > result in NO POSITIVE crankcase ventilation. The blowby gases will be
> > vented out to the cars intake (before the TB).
>
> Interesting. Through what aperature?

He's talking about, for example, the breather hose on various 1990s Civics and
other Hondas. It connects the region contained by the valve cover to the air
intake just upstream of the throttle body.

For a schematic and drawings of this, see
http://www.honda.co.uk/owner/CivicManual/pdf/11-109.pdf

A lot of web sites that discuss crankcase ventilation have a similar schematic.

But merely having an "alternate" escape route is not enough to maintain the same
crankcase pressure that would be present were the PCV valve operating correctly.

On Wed, 04 Aug 2004 22:00:10 GMT, "Steve Bigelow"
<stevebigelowXXX@rogers.com> wrote:

>
>"Leon" <Curb_Weight_69@hotmail.com> wrote in message

>> 1. The crankcase is not a sealed system. A clogged PCV will only
>> result in NO POSITIVE crankcase ventilation. The blowby gases will be
>> vented out to the cars intake (before the TB).
>
>Interesting. Through what aperature?
>
Sorry, I meant a clogged PCV *valve*. Then the blowby would go
through the little tube from the top of the valve cover to the intake,
before the TB.

Bye,
Leon

On Wed, 04 Aug 2004 22:24:02 GMT, "Caroline"
<caroline10027remove@earthlink.net> wrote:

>"Leon" <Curb_Weight_69@hotmail.com> wrote
>> 1. The crankcase is not a sealed system.
>
>I don't know what you mean. For one, I call the oil pan gasket a seal that may
>be compromised because of excessive crankcase pressure.

There is a little breather tube that goes from the top of the valve
cover to the intake, before the TB. This is part of the crankcase
ventilation system and if it's not clogged the crankcase pressure will
never blow out any seals.

>> A clogged PCV will only
>> result in NO POSITIVE crankcase ventilation. The blowby gases will be
>> vented out to the cars intake (before the TB). - No increased
>> pressure in the crankcase.
>
>Numerous authorities beg to differ. E.g.
>
>"A restricted PCV valve can cause this excess pressure to find new avenues to
>vent, and an oil gasket or seal is usually "blown out" to let this pressure
>escape." http://www.trustmymechanic.com/valve_cover_leak.htm

So, there are some inaccuracies. I should have said: "a clogged PCV
*valve*..." and trustmymechanic should read: A restricted PCV
*system* can...

>"Engine is using more oil than normal. Oil puddles under the car when parked...
>The PCV system is not working properly: Replace PCV valve."
>http://autorepair.about.com/cs/troub...a/bl303a_3.htm
>
>These are merely the very first two hits of a Google search for {"PCV Valve"
>"oil leak"}.

>And here's the Car Talk guys on the subject:
>-----
>RAY: Blow-by occurs when combustion gasses slip by old, worn-out piston rings
>and end up in the crankcase, where they don't belong. Actually, a small amount
>of blow-by is normal and is easily expunged by the crankcase ventilation system.
>But on old heaps (i.e., yours), worn-out rings can let so much stuff into the
>crankcase that the ventilation system just can't handle it.
>
>TOM: So the pressure in the crankcase builds up until gasses and oil try to
>escape any way they can. And we often see air-filter housings full of oil, seals
>blown out or leaking, and the occasional dribbling dipstick.
>
>RAY: The solution is an engine rebuild, which would include a ring job. But
>before you consider that route, or ditch the truck, I've got two other things
>for you to try.
>
>TOM: If you've lived a really good, clean life, your problem might just be a
>plugged crankcase ventilation system. So have your mechanic check out your PCV
>valve and the hose it's attached to. ...
>-----
>http://lang.motorway.com/home/articles/qandaoilydip.asp
>
>The fact is that a clogged PCV valve results in one less possible avenue through
>which blowby gases may escape. The average pressure in the crankcase of course
>will tend to be higher as a result.
>
>Also, you might want to consider that how serious oil leakage may be when a PCV
>valve is clogged will likely vary from one car design to another.

If an engine is producing so much blowby that the breather tube has
trouble venting out, blown seals is the least of one's worry. A new /
rebuilt engine is in order.

I agree with that a "clogged PCV valve results in one less possible
avenue through which blowby gases may escape." That does not mean
that the crankcase pressure (which is pulsing as the NG's guru George
explains) will be significantly higher.

A clogged PCV valve results in just that: no positive crankcase
ventilation. The crankcase gases will just vent out the tube on top
of the valve cover, which is not a small orifice and will not increase
the crankcase's pressure . A PCV system is the equivalent of having a
fan sitting on your house window venting out the stale air. The fan
does not significantly decrease the air pressure inside the house
because there is "another window" (the breather tube) open. That's
all a PCV valve does, vents out the stale air.

>> 2. The ECU may be able to trim the fuel at part throttle using the O2
>> sensor. I have no idead how much air the PCV flows, so the amount of
>> fuel trimming available may not be enough. Ofcourse whenever the O2
>> sensor output is not used by the ECU, you are right, the engine will
>> run richer.
>
>According to my reading, it's very ambiguous as to whether a malfunctioning PCV
>valve may affect correct combustion in open loop, closed loop, or both.
>
>It may depend on the specific car design. There is quite a lot of minor
>variation from one PCV system to another.

Bye,
Leon