I own 4 Toyotas and one Lexus (too many kids)
and the Lexus just threw me for a loop.

'94 Lexus ES300 with 168,000 miles suddenly stalled
while stopped at a light. Rolled to the side and
tried to start it but no luck. All the dash board
lights light up like normal so power was there to the
gauges and starter motor. Waited about 5 minutes and
it started fine with no check engine light. Hooked up
my OBDII laptop and there are no diagnostic codes or
problems recorded.

O2 sensor readings: One looks funny. O2 sensors B1 S1
and B2 S1 plots look fine with sensor voltage (or
current) and fuel trim or lambda both going through a
sine wave dance. Fuel trim staying between 0 and 4.
O2 sensor B1 S2 looks funny: sensor voltage (or
current) on the low side and fuel trim or lambda is
pegged at 100. I didn't know this thing had 3 O2
sensors (at least that's what my computer is trying to
tell me).

There has been an intermittent trouble code about
every 7 months of P0300, P0301 & P0303
(Random/Multiple Cylinder Misfire Detected, cylinders
1 & 3) but no hesitation or performance issues when it
happens. I just clear the codes and wait for it to
come back.

I'm starting to study the service manual but I'm having
trouble figuring out where to start without some kind of
diagnostic code.

Paul.
Phoenix, AZ

"Paul." <paul.blomberg@cox.net> wrote in message
news:RYHQg.192$La2.92@fed1read08...

If there is no check engine light, the likelihood of a code being stored is
pretty low.


If you have 2 catalytic converters, then you probably have 4 O2 sensors - B1
S1, B2 S1, B1 S2, and B2 S2.
In other words, a sensor before and after each catalytic hconverter.

If the catalytic converter is doing its job, the signal from the post-cat
sensors should much flatter than the signals from the pre-cat sensors. If
you look at the factory service manual under DTC P0430, it should show what
the o2 sensor patterns should look like.

The cylinder misfire codes could be caused by ignition system misfires or
from an over-lean fuel mixture. If you have aftermarket ignition parts,
consider using OEM next time you change them because I have seen some
aftermarket ignition parts cause problems. Some aftermarket ignition parts
are fine and some cause problems. I have not been able to detect a pattern
so I recommend OEM ignition parts. A lean-misfire usually brings up other
DTC's unless the pre-cat sensors are beginning to fail, but your scan seems
to indicate that they are OK.

As far as what caused the car to stall, I would check fuel pressure with a
fuel pressure gauge. A fuel pump or fuel pressure regulator that is not up
to stuff or a clogged fuel filter might not deliver sufficient fuel pressure
to keep the engine running and they would not necessarily set a check engine
light. I would check the fuel pump, fuel pressure regulator, and fuel
filter in that order. A failing fuel pressure regulator often causes long
cranking during cold starts, which you did not mention, and a fuel filter
that is clogged enough to starve the engine for fuel would probably not
allow a re-start, leaving the fuel pump as a more likely culprit.
--

Ray O
(correct punctuation to reply)

Ray,

The "funny" sensor is the one after the catalytic converter. Only one
converter on the car. The manual does say that the patterns should look
calmer.

I'll start looking at the fuel delivery system (but I have to buy the tools
first). I got this car from my brother-in-law about 6 months ago so I
really don't know the service history as he also bought it used. Only
things I've done on it is timing belt, waterpump, crank seal, four shocks
and a lot of touch up paint (Colorado car, lots of gravel there in the
winter.)

There is no problem with power of the engine and it easily runs 80 MPH. Car
starts just fine, no long cranking. But I'll check fuel system performance
(any excuse to buy more tools!!)

I'll probably dive into the MAF meter, IAC valve and throttle body and see
how dirty it is and change the fuel filter this weekend. Thanks for the
ideas Ray, at least I have a starting point now.

Paul.


"Ray O" <rokigawaATtristarassociatesDOTcom> wrote

"Paul." <paul.blomberg@cox.net> wrote in message
news:FlJQg.199$La2.130@fed1read08...

If the after-cat sensor is active with a pattern like the pre-cat sensor, I
would imagine that you get have DTC P0420 because the cat is failing. The
cat may be on its way out but not bad enough to set a code yet.


No long cranking tends to rule out the fuel pressure regulator and fuel
filter but the fuel pump can be bad.


If the car idles OK, the IAC valve is probably OK.

If the throttle pedal sticks in the closed position, then the throttle plate
(butterfly plate) in the throttle body may be gummed up and need cleaning
with carb cleaner. A gummed up throttle body will not cause the engine to
stall.

If you do not have a volt-ohm meter, it would be a good investment.

Good luck!
--

Ray O
(correct punctuation to reply)

"Paul." <paul.blomberg@cox.net> wrote in message
news:RYHQg.192$La2.92@fed1read08...

I don't know for sure on yours, but I do come across a similar fault on
Vauxhalls in the uk. 9 times out of ten it is the crank position sensor.

mrcheerful

I'll have to check the wiring on that sensor. It was in the way a lot when
I changed the water pump and timing belt. I may have pulled on it too much.

Thanks,
Paul.

"mrcheerful ." <nbkm57@hotmail.com> wrote in message
news:NNMQg.22868$r61.20742@text.news.blueyonder.co .uk...

> If the after-cat sensor is active with a pattern like the pre-cat sensor,

The after-cat sensor is the same pattern but much less amplitude. I'll
watch it though. Maybe I'll run the car around with the OBD laptop attached
and record the patterns with different RPM's and load.


Good to know!! Once I get the fuel pressure gauge I can check the whole
system out.


Electrical gear I have. Digital and analog VOM, ampmeters, etc. I'm better
at electrical problems than mechnical but I like working on both.

Thanks for the help Ray!!

Paul.

"Paul." <paul.blomberg@cox.net> wrote in message
news:CHcRg.336$La2.144@fed1read08...

Similar pattern but much less amplitute is good because that means that the
cat is cleaning up the nasties. If the patterns match frequency and
amplitude - in other words, the same signal, then the cat is not working.


You can probably diagnose 95% of the electrical components in a car with a
good digital meter, and if you know how to use it, even better!

The crank position sensor that someone mentioned is worth checking out,
although I would imagine that a problem in that circuit would set a MIL and
DTC.

In terms of thinking about problems that would not set a MIL, the fuel pump
is a possibility.

Good luck!

BTW, what kind of OBD laptop are you using and where did you get it?
--

Ray O
(correct punctuation to reply)

I use an old laptop and plug in an adapter into the OBDII connection. It
allows me to see plots of O2 and several other systems. It also will log
data and save it for review. Viewing and resetting trouble codes is easy.
I think it only reads the power train codes (Pxxxx).

The connecting cable came from OBDII Automotive Diagnostics
http://obddiagnostics.com/index.html and the software and upgrades are free
with the converter purchase (OBDII interface $83; CAN interface $77). He
also sells the parts if you want to make it yourself and the electrical
drawings/schematics are on his site for free.

One work of caution though, the OBDII connection needs a serial port to plug
into. The newer laptops do not come with a serial port anymore. That's why
I use an old laptop. The older ones are readily available and are more
bullet proof that the newer laptops (2 to 3 year life expectancy before
hardware starts to fail on the high end units). Biggest problem with the
old laptops is the batteries are old and don't hold a charge and I'm too
cheap to buy new batteries.

The unit got a nice write up on
http://www.4x4wire.com/toyota/4Runner/tech/BR-3/ . There are some reviews
of connecting cables at
http://www.obd-codes.com/reviews/sh...php/cat/4/page/ .

Paul.


"Ray O" <rokigawaATtristarassociatesDOTcom> wrote

"Paul." <paul.blomberg@cox.net> wrote in message
news:WufRg.350$La2.102@fed1read08...

Thanks for the info! I have a couple of old laptops sitting around, maybe I
can put them to better use than as a doorstop.

I'm not sure that I can justify another scanner, even though it is better
than the one I have, especially since you can check just about everything
out with a DVM, but maybe for the next go-around...

--

Ray O
(correct punctuation to reply)