95 Camry Ignition problem hard to start

On Feb 20, 10:42*am, Mark > wrote:
> On Feb 20, 10:03*am, "Bill" > wrote:
>
>
>
> > > Also I put it in ECM test mode where is sets codes without delay.
> > > It
> > > set a code 31 twice in that mode, which is MAP sensor. *I monitored
> > > the signal voltage out of the MAP sensor and it is appears perfect,
> > > I
> > > as watching it on a scope even while the car stalled.
>
> > And where did you monitor this from? The MAP sensor itself?
>
> > There would be wires going from the MAP sensor to the ECM as well as
> > connectors. Perhaps there is a loose or poor electrical connection or
> > a wire is grounding out to a sharp metal object.
>
> > A diagnostic code for a sensor means there could be a problem with the
> > sensor and/or a problem with the wiring from that sensor to the ECM.
>
> > A *nasty* problem is that someone stuck a too large test probe into a
> > female connector and that terminal no longer gets a good grip on the
> > male pin.
>
> Bill,
>
> I monitored the MAP sensor output directly on the wire right next to
> the MAP sensor. *I agree with you, the next step is to monitor the MAP
> voltage right at the ECM. *I removed the glove box then ran out of
> time yesterday. *That will be the next step.
>
> But it's starting to look like an ECM issue. *I ordered a cheapie on
> EBay.
>
> Mark

I replaced the MAP sensor with a junk yard part...no change...

Next step...
The car recently developed an exhaust leak at the front pipe to
manifold flange. There is chance this is effecting the O2 sensor so
I'm having that fixed... and we'll see what happens..

Mark

> I replaced the MAP sensor with a junk yard part...no change...
>

Try replacing the wiring and the connectors to the MAP sensor.
This is like a table lamp in a house which is not working. Someone
replaces the table lamp and it still does not work. But then they
replace the worn out electrical outlet, then it works! Or "jiggle" the
plug and it works. Connectors and wiring can have problems....

FYI - Research what would cause a diagnostic code for the MAP
sensor...

On Feb 22, 1:04*pm, "Bill" > wrote:
> > I replaced the MAP sensor with a junk yard part...no change...
>
> Try replacing the wiring and the connectors to the MAP sensor.
> This is like a table lamp in a house which is not working. Someone
> replaces the table lamp and it still does not work. But then they
> replace the worn out electrical outlet, then it works! Or "jiggle" the
> plug and it works. Connectors and wiring can have problems....
>
> FYI - Research what would cause a diagnostic code for the MAP
> sensor...

thanks Bill..

I'm looking for more in depth info...

Can a MAP code get set as a result, not a cause, i.e if something else
casues the engine to stall and or backfire, can that unexpected
pressure set a MAP code even though nothing is wrong with the MAP
system?

Can an exhaust leak at the front pipe flange cause the O2 reading to
gradually get the ECM calibrations screwed up enough to cause these
symptoms?

The symptoms also seem to fit a distributor pickup coil problem but no
code has been set for that.

I know in the end it will be something simple that caused this weird
sequence of problems...

Mark

"Tegger" > wrote in message > That's counter-intuitive,
actually.
>
> The coil needs a certain number of milliseconds to saturate. That number
> of
> milliseconds is constant, regardless of engine speed. One drawback of the
> old points-and-condenser system was that actual coil-charge time varied
> with engine RPM (shorter at high-rpm). Modern electronic systems do not
> have this issue.
> Tegger

I think you are just a little off the tangent here.

The old Kettering systems (points and condensor) had to approach saturation,
and that TIME was pretty much constant regardless of RPM.
What I think you meant to say was that with higher RPM, these old systems
did not have enough time to satisfy the RL constant and ignition performance
dropped off.

Some of the newer systems dont use this principle at all. F. eks. a
capacitive discharge system charges the capacitor under high voltage
conditions, so the time function is not as important. It fires a coil as
a stepup transformer (approximately).. There are other variations.

On Feb 22, 2:05*pm, Mark > wrote:
> On Feb 22, 1:04*pm, "Bill" > wrote:
>
> > > I replaced the MAP sensor with a junk yard part...no change...
>
> > Try replacing the wiring and the connectors to the MAP sensor.
> > This is like a table lamp in a house which is not working. Someone
> > replaces the table lamp and it still does not work. But then they
> > replace the worn out electrical outlet, then it works! Or "jiggle" the
> > plug and it works. Connectors and wiring can have problems....
>
> > FYI - Research what would cause a diagnostic code for the MAP
> > sensor...
>
> thanks Bill..
>
> I'm looking for more in depth info...
>
> Can a MAP code get set as a result, not a cause, i.e if something else
> casues the engine to stall and or backfire, can that unexpected
> pressure set a MAP code even though nothing is wrong with the MAP
> system?

Yes, anything that can effect manifold pressure can cause a code to
set, ie cam or ignition timing etc.

> Can an exhaust leak at the front pipe flange cause the O2 reading to
> gradually get the ECM calibrations screwed up enough to cause these
> symptoms?

A pre-02 sensor exhaust can drive the mixture rich, but I doubt it
could cause what you described.

> The symptoms also seem to fit a distributor pickup coil problem but no
> code has been set for that.

Were you able to search the wave form library at iatn.net?

HTH,
Ben

"Mark" wrote in message
> Can a MAP code get set as a result, not a cause, i.e if something
> else
> casues the engine to stall and or backfire, can that unexpected
> pressure set a MAP code even though nothing is wrong with the MAP
> system?
>

That is the thing. And it depends on how the diagnostic code is set.
Information on this would be in a Factory Service Manual set of books
for your specific vehicle. Sometimes these books will say that a
diagnostic code is set only if the engine computer is not seeing a
certain range of values from the wires for a sensor.

Like maybe 2 volts to 11 volts is ok or 100 ohms to 1000 ohms is ok on
the wires going to a sensor (not anything to do with your map sensor).
Then if the engine computer sees 0 volts or 0 ohms, then it would set
a diagnostic code for example. (Like a loose connection or a short.)

But other diagnostic codes may be set depending on the reading of
other sensors / information. So in some cases, something else
malfunctioning could cause an errant diagnostic code.

Diagnostic code setting is done with the computer software in the
engine computer. It is whatever they programmed it to check / look for
that determines what will cause the code to be set.

Here is an example of factory service manual information you would see
for a different newer vehicle (not for your vehicle)...
http://www.obd-codes.com/p0106


> I know in the end it will be something simple that caused this weird
> sequence of problems...

Yes it is always something simple... It is finding it which is the
hard part!

> Can a MAP code get set as a result, not a cause, i.e if something else
> casues the engine to stall and or backfire, can that unexpected
> pressure set a MAP code even though nothing is wrong with the MAP
> system?

The number one source of MAP errors are vacuum leaks.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Feb 23, 10:54*am, ben91932 > wrote:
> On Feb 22, 2:05*pm, Mark > wrote:
>
>
>
> > On Feb 22, 1:04*pm, "Bill" > wrote:
>
> > > > I replaced the MAP sensor with a junk yard part...no change...
>
> > > Try replacing the wiring and the connectors to the MAP sensor.
> > > This is like a table lamp in a house which is not working. Someone
> > > replaces the table lamp and it still does not work. But then they
> > > replace the worn out electrical outlet, then it works! Or "jiggle" the
> > > plug and it works. Connectors and wiring can have problems....
>
> > > FYI - Research what would cause a diagnostic code for the MAP
> > > sensor...
>
> > thanks Bill..
>
> > I'm looking for more in depth info...
>
> > Can a MAP code get set as a result, not a cause, i.e if something else
> > casues the engine to stall and or backfire, can that unexpected
> > pressure set a MAP code even though nothing is wrong with the MAP
> > system?
>
> Yes, anything that can effect manifold pressure can cause a code to
> set, ie cam or ignition timing etc.
>
> > Can an exhaust leak at the front pipe flange cause the O2 reading to
> > gradually get the ECM calibrations screwed up enough to cause these
> > symptoms?
>
> *A pre-02 sensor exhaust can drive the mixture rich, but I doubt it
> could cause what you described.
>
> > The symptoms also seem to fit a distributor pickup coil problem but no
> > code has been set for that.
>
> Were you able to search the wave form library at iatn.net?
>
> HTH,
> Ben

CAR IS FIXED !!!!

Turned out it was a bad ignition coil with a carbon track.
It would occasionally arc at the track and mis fire. The clue was
that it was getting worse and worse, then I decided to pull the plugs
and I reduced the gap and it then ran MUCH better but was not really
fixed. That was a definite indication of a spark strength problem
(not timing or fuel). I opened the distributor and inspected the coil
(it's inside the distributor on this car) and saw a crack in the
potting insulation and what looked like a carbon track. I got an new
coil, put it in and the car has been perfect. I hooked up the old
coil on the bench with a 12 volt 5 amp current limited power supply
and pulsed the primary and saw the secondary arc to the crack. QED.

FYI If you ever test a coil on the bench like this by pulsing 12V into
the primary, it was interesting to see that it did not develop a good
spark unless I also connected a capacitor on the primary.

So the car is fixed and I'm a happy camper.

thanks to all
Mark

Mark > wrote:
>FYI If you ever test a coil on the bench like this by pulsing 12V into
>the primary, it was interesting to see that it did not develop a good
>spark unless I also connected a capacitor on the primary.

This is the coolest damn thing. If you actually look at the waveform on
a scope, it's a huge damped sine. The coil has got a ferrite core, so it
really is only effective at high frequencies. You pulse it, and only some
of the high frequency components of that square wave actually make it through
the coil.

BUT... The coil inductance combined with the shunt cap make a resonant
circuit and the resulting damped sine wave makes it through the coil very
effectively.

Kettering figured this whole thing out and it's a hell of an ingenious
idea.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Mark > wrote in
:


>
> CAR IS FIXED !!!!
>
> Turned out it was a bad ignition coil with a carbon track.
> It would occasionally arc at the track and mis fire. The clue was
> that it was getting worse and worse,



Which you might have discovered days ago had you actually pulled a wire and
WATCHED the spark instead of playing with your toys.



--
Tegger