Hyundai Excel Ambiguous Codes Read - continued

Sorry that should be Air Flow Sensor and not Mass Air Flow sensor (1995
and later)

Sorry that should be Air Flow Sensor and not Mass Air Flow sensor (1995
and later)

Replace the AFS or NOT.

AFS
I believe that the Haynes instructions are misleading and wrong. Many
sensors including the AFS, cannot be disconnected and tested but must
be backprobed. The voltage between 6-5 is power and 3-6 is output, not
vice versa. The scope shows a great looking square wave which varies in
frequency as airflow. The Karmen Vortex sensor is a complicated piece
of engineering but it seems to still work as designed.

CKP
Crankshaft position sensor (in the distributor) seems to be working as
speced and gives a regular looking square wave. The code being
registered appears consistently to be 1,5 = Motor position sensor. How
is this different from "Crankshaft position sensor" and "Camshaft (TDC)
position sensor"? Is it possible that the code is an indication that
the cam and crank are not synced? Would this engine run if the two were
not synced?

Oxygen sensor and street behavior
The oxygen sensor swings between .2-.8V when idling for short periods
of time, however, moves to the range .9-1.0V when the gas pedal is
depressed.

Next steps
I will replace the ECU when I get one (used) and will continue to test
sensors.

=======
=======
wrote in message:

> Next steps
> I will replace the ECU when I get one (used) and will continue to test
> sensors.

========
========
I do some work for a used car lot.

They've brought me 2 used ECUs in the last 8 months to install because
they didn't want to spend the money on a reman unit.

NEITHER of the 2 vehicals were repaired by installing the used ECUs.

The first was a Honda Accord. When I told them the ECU was bad, gave
them
a replacement price, they requested for me to install the used ECU. No
prob.
They paid my labor on the diagnosis. Supplied the used ECU. I
installed it.
Then I called them up and asked if they wanted me to charge another
$289
to diagnose the symptoms that the vehical had now that the used ECU was

in it, or would they like to opt for a reman? Their call, not mine. I
ended up
letting them provide a reman unit, just to prove a point.

The second vehical was a Nissan Pathfinder. When I called them up and
told
them the ECU was bad, they did the same thing. So did I.
I got paid for my diagnosis, paid to install their used ECU, made my
phone call
and asked them if they wanted me to charge them for diagnosing the new
symptoms
on the truck, or if they would like ME to install the ECU. They took
the vehical,
put a reman ECU in it. THEN, brought it back to me because they
couldn't figure
out why the damn thing was'nt spitting out codes, tranny was now
shifting,
but the idle was rough as a cog. I got paid $129 for driving the truck
for 2 hours
to a seminar. (Relearn the computers memory) Something that would
have been
done if they had allowed me to install the ECU in the first place.

But, if they're customers don't mind, neither do I. lol



any whoooo.......
this is just a warning to you. Make sure that the ECU get has a
warranty.

Pull codes on the vehical BEFORE you change the ECU, and make special
note
of the symptoms the vehical has.

Then, pull codes on the vehical AFTER you install the used ECU if you
have
further drivability concerns. That's the quickest way to detect a bad
ECU when
using used ones on interchanges. I've seen bad used units quite a bit.
Not all
the time, but enough to where I will NOT use them. Unless the customer
supplies
it, and then I get payed for my initial diagnosis and the jobs done.
When the used
ECU is installed, you HAVE TO...look at the vehical as a new job if it
poses ANY
symptoms what so ever. It's the foundation of diagnosis. Diagnose the
problem
in a systematic way, each time, every time. And, never "guess" that
the part you
just installed is good when it could be bad.


again,
just a warning and some advice.


hope all works out well for you.

wrote:
> Replace the AFS or NOT.
> AFS
> I believe that the Haynes instructions are misleading and wrong. Many
> sensors including the AFS, cannot be disconnected and tested but must
> be backprobed. The voltage between 6-5 is power and 3-6 is output, not
> vice versa. The scope shows a great looking square wave which varies in
> frequency as airflow. The Karmen Vortex sensor is a complicated piece
> of engineering but it seems to still work as designed.

As previously stated. You still aren't addressing the possible Baro
code, and the fact that there is a Baro sensor built into your AFM,
which could shift fuel strategy if out-of-range. All you have to do is
test from the Baro wire to ground as determined by your wiring diagram.
I think they are terminals 6 and 4 (from memory)

> Next steps
> I will replace the ECU when I get one (used) and will continue to test
> sensors.

If this doesn't fix it, you may well have spent more than the car is
worth. Keep things in perspective before you do something pound
foolish.

Toyota MDT in MO

>
> Oxygen sensor and street behavior
> The oxygen sensor swings between .2-.8V when idling for short periods

This is about a normal operastion for an o2 sensor; it could be lazy or have
other problems but for interner diagnostics it appears to be ok



> of time, however, moves to the range .9-1.0V when the gas pedal is
> depressed.
But if you hold 2000 rom does it start switching again or does it stay at
those numbers.
Near 1 volt the o2 sensor is seeing a rich condition; OK if you just romped
on it; but it should stabalise and start going from .2ish to.9 ish. (do not
be concerned about where it it in this range.0-.9 as long as it goes from
low to high. IF it stayes at one range or another then IS the O2 sensor
sticking or is it actually reading the resulth of the post combustion burn
and is showing you a clue to the real problem.
No one said auto diagnostics was easy.


--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist

http://autorepair.about.com/cs/troub...l_obd_main.htm
http://www.troublecodes.net/technical/



>

I feel a little bit stupid for not being able to tell black from blue
smoke however, It now appears that there is a mechanical problem. My
cousin (a BMW tech) has suggested oil control rings may be a problem
after looking at the car and the results of my efforts.

Symtoms:
Idles roughly
Starts with blue smoke
Accelerates with blue smoke
Some smoke when idling.

Sensors tested:
Air flow sensor - OK
Crank position - OK
Temperature sensor - swings between 10K and infinity after 5 mins - not
OK but will leave it for now
Fuel pump, injectors, pressure valve- tested as suggested by Haynes and
my cousin -OK
Plugs - clean after 20 mile of freeway driving black after city driving
idling
Leak down - 1-10%; 2-6;3-10;4-20 (leaking through crankcase and
cylinder head)

The initial cylinder pressure readings plus my lack of observational
skills put me off initially, however, I will do a re-ring and re-valve
stem seal with the engine in the vehicle.

I would like to know how the sellers mechanic made it pass Aircare
(they tried twice, the second time it passed with the NOX readings
raised from 84 ppm to 517 and the idle HC lowered from 2000 ppm to 16)
and whether a recent timing belt replacement had anything to do with
it.

Thank-you for your help. I'll keep the group posted.