Re: modifying and evaluating my 95 Previa

On Aug 16, 9:39 pm, "Ray O" <rokig...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
"Joe" <in2d...@xxxxxxxxxxx> wrote in message

news:34907c70-4492-4f28-a313-2ac8d65cf012@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Aug 16, 9:33 am, "Ray O" <rokig...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:



"Joe" <in2d...@xxxxxxxxxxx> wrote in message

news:1b6ef751-e4c3-445b-8611-53bd869820c8@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

*********
Hopefully, the new PCV valve cures the oil pumping problem. If if
doesn't,
follow the hose all the way to the intake manifold or throttle body.

I lose the hose when after it enters the metal tube. It seems to
reenter the top of the engine toward the driver side, if I'm looking
at the right one. Its hard to follow them between access panels.

I'm not sure how to evaluate the blow by. I still feel it blowing
fairly strong out the fill tube if I have the cap off. It seems to
blow more when it warms up and idles down. But i cant say if its more
or less than before. I wiped the cap off and cleaned off inside the
neck real well so I can see if oil builds up there again. Is there a
more definite way to measure? How much is too much?

I think the rubber hose that vents just below the oil fill cap enters
the intake housing/assembly (whatever its called) near the air filter.
At least i assume that is it, I cant trace that one all the way
either. There is a metal tube ca 1/2" dia (labelled HOT) that keeps
popping out of the rubber hose it inserts in there, just before the
filter, and the metal tube mouth has a coating of oil on it. But there
is no oil inside the air filter or housing, as I noted before. I
assume this is the other end of the hose that vents just below the
fill cap. I dont know if this could be part of the problem but
although it has oil in it it seems unobstructed.

****
OK, time to start working backwards. Check the opening where the metal
tube/hose connects near the air filter housing and make sure that the
opening is not restricted at the connection to the housing.

I am not aware of any actual specification for measuring blowby, but there
are specifications for wet/dry compression tests and leakdown tests to
evaluate valves and rings.
--

Ray O
(correct punctuation to reply)

Everything looks OK on that tube. BUt my @#$% check engine light came
back on.
 drove for most of a day with it out. I presume this is going to be
EGR again. Argggg.
Nobody around here will check it without charging me 70 bucks.  What
do I need to know before buying/using an OBD II tool? I can buy one
for less than 70 on ebay but I dont know if I need seperate chips or
special knowledge to use one.

**********
A basic OBD II scan tool will read, display, and clear standard OBD II codes
and will work on your Previa.  (I have an Actron basic OBD II reader).   One
of the requirements for OBD II is that the connector is standard across all
makes and models after 1996 model year (some vehicles adapted all or part of
OBD II earlier).  The 1995 Previa is partially OBD II compliant.

A code reader that is CAN compliant will be useful for a wider array of
vehicles, including future Toyotas, and this is the minimum that I
recommend.

As you move up in capabilities and price, you get:

- Pending codes - Many OBD II codes have 2-trip detection logic, where the
vehicle's electronic control unit (ECU) has to see the same condition on 2
consecutive trips before it illuminates the check engine light.  The ability
to see pending codes is useful to find out if  your fix has worked or not.

- Drive readiness monitor - This feature will tell you if, after clearing
codes, the vehicle has been driven far and long enough under the right
parameters so that every sensor has been checked at least twice, and will
pass an emissions check.

 - Sensor freeze frame and/or real time data - You can check the actual
values being transmitted from the sensor to the vehicle's electronic control
unit, or ECU.  While any sensor can be checked with a multi-meter, some are
difficult to reach or access, making this feature convenient and
time-saving.  This would be useful in the Previa, where some sensors are
difficult to reach or even find.

- Manufacturer specific codes - Automakers have some specific codes in
addition to standard OBD II codes but the scan tool has to have the
capability of reading them.

If I were shopping for another OBD II tool, I would want all of these
capabilities because I look at a fair number or vehicles. Someone who only
uses a scan tool occasionally probably doesn't need all those capabilities.

Some code readers give you a text interpretation of the code instead of just
the code that you have to look up the code meaning.  The scanner should come
with a book that lists all of the codes.  Plugging in and OBD II scanner and
checking codes is very easy and only takes a minute, but you will still need
some kind of manual so that you know how the vehicle is designed to monitor
and check for a particular code.

For example, for P0401 - insufficient exhaust gas recirculation detected,
some vehicles use an EGR gas temperature sensor placed in the EGR tube
between the EGR valve and intake manifold to monitor EGR flow.  The
temperature sensor varies voltage with temperature.  The more exhaust gas
flowing past the sensor, the higher the temperature.  If the temperature is
too low, the system interprets that as insufficient EGR flow.  It is
possible that the EGR flow is actually low, or it is also possible that the
sensor is giving bad voltage output.

Some other vehicles use an EGR valve position sensor to monitor whether the
EGR valve is open or closed, so it is possible that the EGR flow is actually
low, or that the sensor is bad.

So, for P0401, you have to check whether the EGR valve is functioning
properly, check the systems that control the EGR valve like a vacuum
modulator or vacuum control valve, vacuum hoses, etc. and if the EGR control
system is working, then check the voltages or operation of the sensors.

Bottom line, you will need a repair manual for your vehicle to go along with
and OBD II tool to properly diagnose a condition.
--

Ray O
(correct punctuation to reply)

I would probably only use the tool for reading codes to ensure that
new ones haven't cropped up (what with the light on permanently..),
and to clear codes before taking it to shops that wont work on the
vehicle without taking a reading if the check engine light is on.
Fortunately I dont think I'll need it right away.

I took the Previa in to another shop today. They did a compression
test and all were between 150 and 162. They didnt think I had any
engine worries or needed a leakdown, so I'm heading off to the Yukon
tomorrow and never going back to the first shop that told me I had
blow by and a tired engine again....IThey suggested today my fuel
filter might have caused the sluggishness in recent months (which I
havent felt lately).

Where is the filter on this? Now that I know I'm keeping it I will buy
a shop manual....I recall my 91's filter being along the side
somewhere in the middle, so I'll look there first. I should probably
bring one along on the trip just in case...
.

Relevant Pages

  • Re: modifying and evaluating my 95 Previa
    ... the new PCV valve cures the oil pumping problem. ... EGR again. ... A basic OBD II scan tool will read, display, and clear standard OBD II codes ... Sensor freeze frame and/or real time data - You can check the actual ...
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  • Re: modifying and evaluating my 95 Previa
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