"TeGGer®" <tegger@istop.c0m> wrote
> > As far as time to change the PCV, I think, well hope, that might me
> > premature. Does anyone know if cleaning it out is easy/practical?
> >
> >
>
>
> With the car fully warm, squeeze the PCV valve hose shut with a pair of
> pliers. If the idle changes or the valve clicks, the valve is fine.
>
> The idle will change, then smooth out again as the ECU adjusts the air
> mixture. If the idle does not change when the hose is pinched shut, the
> valve is plugged. Either way, a blocked PCV valve is not your problem
here.
> A blocked PCV valve will not cause the sort of decrease in gas mileage
that
> you are experiencing.

An old or blocked PCV valve may very well cause a significant decrease in
gas mileage. But I'm doubtful the PCV valve is behind the stalling.

Even if it's not plugged, the PCV valve's parts wear over time. Change it
with an OEM one. It's not hard to do, like Chopface said. You can do the
test that Tegger describes above; you should also hold it for at least 30
seconds and listen for a "click" sound. If there's no click sound, then the
valve isn't working.

My 1991 Civic was getting poor gas mileage around spring 2003. The PCV
valve had never been replaced. I didn't know enough to do the tests above;
I just replaced it, for around $20 with a dealer one. The old (and
original) one was chock full of waxy buildup. My mileage shot up 10-20%. It
was very noticeable. Other reports on the net document that a
malfunctioning PCV valve most certainly may affect gas mileage. It messes
up the ECU's take on the engine's condition, and the computer sends a
signal that results in rich (=excessive fuel) fuel-air mixtures.

I now clean out my PCV valve every few months or so. It typically has a few
specks of gunk in it. And I do mean little specks--Q-tip pick-able. It
would take a long time for this to build up to anything that would block
it. I remove the valve completely about once a year and spray it with a
little WD-40, too.

> You need to get the Check Engine light code. Pull the carpet back from
the
> passenger footwell until you see the ECU. Turn the ignition to ON (but
not
> to START), and count the sequence of long and/or short blinks from the
> ECU's red LED. Report back here.

Ya, really. Start there. Various online manuals describe this.

If it's the O2 sensor, the good news is that it's very cheap to replace on
the 1991 Civics. I have a 1991 Civic and replaced the O2 sensor last
summer, as a pre-emptive measure and because it was so cheap, around $45
total, using an online site that had OEM sensors.

And replace that timing belt!