Ford EEC-IV Problem
flde...@mmm.com
OK (111), as does the KOER check. A 172 (lean) code is stored in continuous memory. Ford replaced the oxygen sensor,but
won't do anything else under the emissions warranty. The Check Engine Light seems to come on after approximately 30 minutes
of driving and it can either be at highway speeds or while driving slow. There are no noticeable changes in how the truck drives,
but the gas mileage seems lower than previous and the exhaust pipe is black indicating that it is running rich. I have removed the
connector from the EEC-IV and checked the pins of the connector (all OK) and have done the same with the connector that is
between the engine and the large cable that runs under/through the fuse box on the wheel well. The engine coolant temp sensor
and the air charge temp sensor both have the correct resistance.
Can anyone suggest what to try next? I assume that something is causing the EEC-IV to think that the engine is running lean,
then the EEC-IV is trying to make it richer (why the exhaust pipe is black and the mileage is down). It sounds like the oxygen
sensor, but it is new! Maybe the next step is to measure the oxy sensor output with a high resistance voltmeter and see what
the output is running.
Fred
George B
>I have a 1992 F-150 with the 4.9L I-6 engine that has started to periodically
light the Check Engine Light.
Check out this scenario...you get a spark that arcs through a plug boot to the
manifold. The cylinder just misfired, it dumps an unburned fuel/air charge to
the exhaust manifold. The O2 sensor sees this as a lean condition!
(Remember...it is an OXYGEN sensor not a FUEL sensor). The computer then tells
the injectors to go richer (stay open longer). If the arc persists you could
go to a FULL RICH condition that can get a cat mighty hot. All the while you
are setting a LEAN code while the engine is actually flooding.
ANY excess air entering the exhaust system AHEAD of the O2 sensor can cause
this O2 sensor runaway condition.
The arcing would normally be noticeable as a drivability problem.
A plugged EGR tube could also cause a lean sensor code with excessive gasoline
usage. The valve itself might be working OK but the tube that carries the
exhaust to the valve could be plugged (with soot) or damaged (leaking
somewhere). This would give no noticeable driveability problems.
This scenario would go as follows (EGR plugged)...vehicle accelerating or
cruising, reaches operating temp, computer tells EGR to open...valve opens but
no EGR effect. Mixture is now too lean...computer opens the injectors a bit.
Or EGR tube leaking...air being sucked into exhaust during negative pressure
periods in exhaust fools O2 sensor into a lean condition causing engine to run
too rich. Also...EGR valve sucks in air instead of O2 depleted exhaust
gas...again making mixture lean.
This is one of those problems that can be a real pain in the hips to
troubleshoot because you can not get a data stream out of the EEC IV to see
what the computer THINKS is happening.
George Bonser
gr...@cris.com
-Bodnar,B.L.
Good comment from George. On the other hand, you can always run the Key On
Engine Running (KOER) diagnostic and see what it picks up. I used KOER in my
(ex) Mustang regularly to spot bad electrical connections in the valves
controlling the air injection system.
Also, if the scenario George described (the misfiring) is present, the Ignition
Diagnostic Monitor (IDM) fault code will probably be set since the computer
will not see a proper return wave from the ignition coil's primary (I've had
IDM codes set during engine misfire -- I don't know what algorithm Ford used in
this portion of the diagnostics, but it's certainly non-trivial).
Cordially,
Bohdan Bodnar
George B
boh...@ihgp1.ih.att.com (-Bodnar,B.L.) wrote:
On the other hand, you can always run the Key On
>Engine Running (KOER) diagnostic and see what it picks up. I used KOER in my
>(ex) Mustang regularly to spot bad electrical connections in the valves
>controlling the air injection system.
The tests can only verify that all actuators are operating....they do NOT
verify that anything is FLOWING THROUGH THEM or WHAT is flowing through them.
The EEC-IV is only aware of the fact that a spark was ATTEMPTED not if the
plug actually fired...what is the difference betewwn an arc at the plug gap
and an arc at the plug boot?
The strategy here is a basic one-shot logic. If a pulse does not occur to the
ignition module within a period of time...the one-shot times out and a code is
set. This is probably in software due to timing differences needed for
different RPM. All this code says is that a PIP pulse was missed. If the
ignition is commanded to fire within the proper time window...no code is set,
regarless of where the arc occured...at the plug or within the coil...the
system can not tell.
EEC-V might be a different story.
George Bonser
gr...@cris.com
Frank van Son
>Fred
In Europe, Ford, at least on the 2.0i DOHC with EEC-IV, had problems
with poor connection of mass to the sensor. Due to corrossion the
exhaust made bad connection to mass, making the signal from the sensor
being 'disturbing' for the EEC-IV. By connecting/soldering in the
EEC-IV plug the mass of the sensor to a real mass (in my case it was
pin 49 being sensor mass and I BELIEVE pin 20 being mass) the problem
had been solved. PLEASE CHECK THIS UP WITH YOUR FORD DEALER. THIS
PROBLEM OCCURED ON FORD SIERRA'S 1990-1994 AND MAYBE IT DOES NOT APPLY
TO YOUR F-150 MANUFACTURED/USED IN THE US. FURTHERMORE, PLEASE CHECK
THE PIN NUMBERS I MENTIONED, IT COULD BE THAT IN THE US ANOTHER PIN
SETTING IS BEING USED FOR THE EEC-IV.
Met vriendelijke groeten,
Frank van Son
:-)
Het broeikas-syndroom is de droom van elke rechtgeaarde calvinist:
eindelijk mogen we ons schuldig voelen over het feit dat we ademhalen.
:-)
George B
>Diagnostic Monitor (IDM) fault code will probably be set
IDM is used ONLY on DIS (distributorles ignition systems) It is an encoding of
1) PIP 2)CID 3)SPOUT and 4)coil pack current. It is used on the 2.3 dual
plug, 3.0 SHO, and 3.8 SC DIS systems and the EDIS systems. Again...it
measures signal timing and coil current. It is handy for finding bad coil
packs and missing igniton electronics but not much good for arcs along the
plug wires as these do not affect coil current. There is no measurement of
spark voltage or any timing of reflected waves....this would set false codes
if longer/shorter wires were used.
George Bonser
gr...@cris.com
GBlessing
that it told the coil (actually module) to fire and the return pulse from
the coil primary wasn't consistent with a normal firing.
J Blessing ASE Master Tech
flde...@mmm.com
>
> Check out this scenario...you get a spark that arcs through a plug boot to the
> manifold. The cylinder just misfired, it dumps an unburned fuel/air charge to
> the exhaust manifold. The O2 sensor sees this as a lean condition!
I failed to mention that the truck has very low mileage on it. It only has 8800 miles on the odometer, but has been driven at least
weekly. The plug wires seem like new and I can not detect (visually) any evidence of leakage. Driveability seems the same as it
was when new, but I've always thought the I-6 is slow to accelerate. I have noticed a drop in mileage from around 16-18 down to 12-14
and the exhaust pipe is black, rather than gray.
> A plugged EGR tube could also cause a lean sensor code with excessive gasoline
> usage
I have taken off the EGR sensor and checked to make sure that it works. The full resistance is around 3500 ohms (book says 5000)
and the minimum resistance is around 350 ohms (book says 100). Could be a misprint in the book, as the throttle position sensor is
stated to be 3500 and 100 ohms. Also applied vacuum to the EGR valve with my hand over the hole normally plugged by the sensor,
then took hand off and heard the clank as the valve closed. This wouldn't prove that the gas is getting through the plumbing, but at
least the valve moves. I will next try applying vacuum to the EGR valve with the idle stabilizer disabled and see if I get a drop in RPM.
Could injectors cause this problem? When the truck was new, I had a noticeable clicking that changed speed with RPM. Ford
couldn't find it, and it finally went away. They thought it might be injector noise being transmitted up into the cab. Since the injectors
control mixture by the open/close ratio, could it be that one injector is not fully opening all of the time? This might be caused by
corrosion on the connector or ?????. Just a thought.
I do a lot of electronics trouble shooting, but it is much easier with the device on the bench and relatively good control of the operating
parameters.
Thanks for the help.
Fred L. DeRoos
-Bodnar,B.L.
>In article <DC9y1...@ssbunews.ih.att.com>,
> boh...@ihgp1.ih.att.com (-Bodnar,B.L.) wrote:
>>Engine Running (KOER) diagnostic and see what it picks up. I used KOER in my
>>(ex) Mustang regularly to spot bad electrical connections in the valves
>>controlling the air injection system.
>
>The tests can only verify that all actuators are operating....they do NOT
>verify that anything is FLOWING THROUGH THEM or WHAT is flowing through them.
>
This is incorrect. The computer uses the O2 sensor to determine whether the
exhaust is leaned or not -- it does NOT use current sensing to determine
whether the valves are actuated or not. This won't determine whether the
catalytic converter is being fed air, but certainly will provide fault
detection for the TAB and TAD solenoids, valves, air pump, etc. Put
differently: most of the electrical and pneumatic circuits have fault
detection capability.
If you don't believe me, try running the KOER test with the O2 sensor cold and
see the test fail. Or, run the test with a hot sensor and disable the
portions of the air injection system and see what happens. You won't detect
downstream pneumatic circuit failures (e.g., cracked tubing at the catalytic
converter) but you certainly will have detection at the upstream portion.
>The EEC-IV is only aware of the fact that a spark was ATTEMPTED not if the
>plug actually fired...what is the difference betewwn an arc at the plug gap
>and an arc at the plug boot?
Simple -- what's the energy requirement to fire a sparkplug in a compressed
gas environment as opposed to the energy requirement to fire a something (e.g.
a short across a boot) at atmospheric pressure? The latter is much lower than
the former. This is reflected as a low impedance across the primary side of
the coil (which is nothing more than a pulse transformer). This results in a
reduction in the pulse height on the primary side of the coil (pull out any
electrical engineering textbook which covers basics of transformer operation
and you'll see this in the equations). If this reduction is great enough, the
voltage comparator in the computer will not see a pulse of proper amplitude
==> IDM code set.
>
>The strategy here is a basic one-shot logic. If a pulse does not occur to the
>ignition module within a period of time...the one-shot times out and a code is
This is correct. Here's the rest: the IDM signal is taken off of the primary
side of the ignition coil. It goes via a resistor (in my vehicle, it was 22k
ohms) back to the computer. Pull out a wiring diagram for a typical Ford
computer system and you'll see this.
If the computer was merely looking at the Profile Ignition Pickup signal,
you'd lose fault detection capability for the module, ignition coil, and much
of the secondary side of the ignition system. Consequently, PIP *is not*
looked at. The PIP signal may be present and the IDM code will still be set.
My experience was that I could set the IDM code by disconnecting the ignition
coil or shorting its secondary (note: PIP signal is present in this case).
Also, misfiring would set the code. This was on a 1986 Mustang w/FBC and
EEC-IV. Perhaps, there are misfiring cases which would not set this code;
however, I never ran across them.
>set. This is probably in software due to timing differences needed for
>different RPM. All this code says is that a PIP pulse was missed. If the
>ignition is commanded to fire within the proper time window...no code is set,
>regarless of where the arc occured...at the plug or within the coil...the
>system can not tell.
>
>EEC-V might be a different story.
>
>George Bonser
>gr...@cris.com
Much of this IDM stuff is covered in Ford's technician training material
(which I have someplace at home). The rest can be inferred by knowing
something about pulse electronics and putting oneself in the engineers' shoes
and asking: if I wanted to detect these types of faults, what would I do?
*WHY* would a 22k resistor be needed to run the signal back to the computer?
etc.
Cordially,
Bohdan Bodnar
-Bodnar,B.L.
>In article <DCBsI...@ssbunews.ih.att.com>,
> boh...@ihgp1.ih.att.com (-Bodnar,B.L.) wrote:
>
>>Simple -- what's the energy requirement to fire a sparkplug in a compressed
>>gas environment as opposed to the energy requirement to fire a something
>(e.g.
>
>
>First the system has NO IDEA how much energy is needed to fire the plug...only
>how much current the coil draws while being "charged". The spark occures when
>the cvharging current is switched OFF allowing the magnetic field to colapse
>very quickly inducing a high voltage to the secondary. This voltage will rise
>as high as necessary to arc. It will go to a billion volts if it needs
>to...but it normally arcs before that. At this stage there is NO current being
>applied to the coil and the system is NOT monitoring coil secondary voltage.
George, READ what I wrote CAREFULLY. *NOWHERE* will you see anything about
"...monitoring coil secondary voltage." Also, I do not need a high-school
level description of basic transformer operation -- I have a a few degrees in
electrical engineering and HAVE designed pulse circuits. If I need references
to some exotic high voltage systems, I can always pick up the phone and chat
with guys who design Zenith's HV power supplies for television sets (former
classmates).
The similarity between automotive ignition systems and television high voltage
power supplies (or any step-up switching power supply using PWM control) is
very high.
The fact is that many aspects of the operation of the secondary side can be
inferred by looking at the reflected signal on the primary side of a
transformer -- you can find the pertinent equations in ANY undergraduate book
dealing with basic circuit design (do you want references?). The combustion
chamber and sparkplug merely form a gas diode (non-linear load) whose
effective impedance is reflected back to the primary side of the ignition
coil. The cathode is the center electrode whereas the anode ("plate" if
you're into vacuum tubes) is the outer electrode of the sparkplug. Understand
this and you'll immediately understand WHY the ignition coil has to be wired
correctly (w.r.t. polarity) and you'll immediately understand what I meant
about "energy requirements." The term of interest to automotive technicians
is "reserve energy."
>
>
>The Ford ignition system monitors coil current...which happens BEFORE the
>spark occurs. The system can NOT TELL WHERE THE SECONDARY ARC OCCURED PERIOD.
This "variable dwell" is used BY THE IGNITION MODULE -- *NOT* BY THE COMPUTER.
The computer has NO information as to pulse's duty cycle the IGNITION MODULE
is using. GM's HEI was doing exactly the same thing in the 1970s.
>It can only tell that a pulse was received from the module, sent to the
>computer, computer sent a pulse back to module, coil charged, and transistor
>shut off. Since an arc then MUST occur there is no sense checking for it. The
>system required to monitor a reflected wave traveling at light speed to
>resolve the arc position within a half inch or so would be beyond the scope of
>the average production automobile.
Please read my previous posting. All that's needed is to monitor the
amplitude of the waveform on the primary side of the ignition coil immediately
after the ignition pulse terminates. The monitoring can commence during the
pulse (e.g., start of ignition pulse, 1/2 way through...) -- time gates aren't
needed. The technology to do this has been
available FOR LEAST 50 YEARS (reference: MIT's RADIATION LABORATORY books,
1946 -- VERY GOOD description of high voltage pulse transformer -- read
"ignition coil" -- design). Still not convinced? Stick a triggered sweep
'scope ("lab scope") at the IDM connection going at the computer and see what
happens to the signal when you (1) short an ignition wire (2) open the
ignition wire. After this, pull fault codes and see what you get. For that
matter, take a look at any automotive technician level textbook on ignition
systems (do you want a reference on that, too? I still have a few of these
books at home) which shows what the PRIMARY waveform looks like.
This stuff isn't rocket science -- the fundamentals have been known for
decades.
>
>The system has no idea if the spark occured inside or just outside the
>cylinder.
>
Hey! We FINALLY agreed on something! Remind me to buy you a coffee if you're
ever in the Chicago area.
>George Bonser
>gr...@cris.com
>
Cordially,
Bohdan Bodnar
bohdan....@att.com
George B
>Simple -- what's the energy requirement to fire a sparkplug in a compressed
>gas environment as opposed to the energy requirement to fire a something
(e.g.
OK here is a sorely needed lesson in Ford ignitiion.
First the system has NO IDEA how much energy is needed to fire the plug...only
how much current the coil draws while being "charged". The spark occures when
the cvharging current is switched OFF allowing the magnetic field to colapse
very quickly inducing a high voltage to the secondary. This voltage will rise
as high as necessary to arc. It will go to a billion volts if it needs
to...but it normally arcs before that. At this stage there is NO current being
applied to the coil and the system is NOT monitoring coil secondary voltage.
It is the SAME principal used in TV "flyback" tranformers. A transistor turns
on drawing current through a coil. The coil at first resists the change in
current as the magnetic field is being built. Once the field is built
completely the coil is said to be "saturated" and becomes like a "piece of
wire". If the current is not limited at this point or unless the transistor
switches off the coil will overheat and it and/or the switching transistor
will burn up. On older systems contact points were used instead of a
transistor and anyone with an old car that left the ignition on with the point
s close can attest to the problems it caused.
The Ford ignition system monitors coil current...which happens BEFORE the
spark occurs. The system can NOT TELL WHERE THE SECONDARY ARC OCCURED PERIOD.
It can only tell that a pulse was received from the module, sent to the
computer, computer sent a pulse back to module, coil charged, and transistor
shut off. Since an arc then MUST occur there is no sense checking for it. The
system required to monitor a reflected wave traveling at light speed to
resolve the arc position within a half inch or so would be beyond the scope of
the average production automobile.
The system has no idea if the spark occured inside or just outside the
cylinder.
George Bonser
gr...@cris.com
George B
I have noticed a drop in mileage from around 16-18 down to 12-14
>and the exhaust pipe is black, rather than gray.
With only 8.8K miles you have a problem that the dealer needs to find. You
mileage should not decrease as a new vehicle is driven it should INCREASE.
I would suggest that you take this vehicle BACK again and demand to know why
the mileage is decreasing and the tailpipe is black.
George Bonser
gr...@cris.com
George B
boh...@ihgp1.ih.att.com (-Bodnar,B.L.) wrote:..stuff..
Ok...follow this.
There is a cut in one of the plug boots. With new plugs, the arc occurs at the
plug gap...as the gap widens the voltage required to fire the gap
increases...eventually the voltage required to fire the plug is EXACTLY the
same as required to arc through the break in the boot. The voltage at the
working cylinders is exactly the same as the malfunctioning cylinder. You can
not diagnose which cylinder is misfiring be measuring either voltage or
current and both the voltage and current are exactly the same between the
functioning and malfunctioning cylinder.
The functioning ones might require 30KV to arc the gap but the malfunctioning
cylinder is arcing the boot at 30KV. There is no way to tell. If the arc is
occuring somewhere along the wire where it has been abraded there may be
little visual spark...just a little twinkle. The current will be the same as
well due to the conservation of energy rules all of the coil packs stored the
same energy (more or less) so if they arc at the same voltage the secondary
current will be the same. The reflected sense pulse will appear identical at
all of the coil packs. All the system can tell is if one cylinder is arching
at a DIFFERENT voltage...not where the arc is occuring...in this case...the
arc voltage is close enough to the others to be within the window and is not
detected as an error.
George Bonser
gr...@cris.com
George B
Lean code set, engine running like crap, cat red hot, system full rich, no
other codes. Only a balance test...the conductive vacuum line as a plug wire
trick, using a test light to ground one cylinder at a time reveals the bad
wire in some cases. Usually due to a spot where the wire has rubbed against
something (hard to spot when running) or a plug boot crack...easier to find.
Vacuum line trick:
Vacuume line is conductive...it is carbon impregnated. (or at least Gates
vacuum line is). Remove the plug wires from the coil pack or distributor and
put a 1-1/2 inch piece of vacuum line on each post. Hook the plug wires up to
the vacuum line. Start the engine...SURPRISE...it runs! OK...take a test light
and ground one side of it ...not an LED test light...must be the old bulb
type. Touch each vacuum line on the plug wires one at a time. As you touch
one...the idle speed should drop. When you hit the dead cylinder the the
engine speed will not change or not change as much as it did when you touched
the others.
This is also useful for finding bad fuel injectors and connecting rod noises.
George Bonser
gr...@cris.com
Donald Wendel
Concerning Ford EEC-IV Problem posted on 07-24-95 at 14:15 :
F>From: flde...@mmm.com
F>
F>I have a 1992 F-150 with the 4.9L I-6 engine that has started to
F>periodically light the Check Engine OK (111), as does the KOER check.
F>A 172 (lean) code is stored in continuous memory. Ford replaced
F>won't do anything else under the emissions warranty. The Check Engine
L
F>Unless you are over 50,000 miles FORD MUST FIX ANY AND ALL EMISSIONS
failures as mandated by the US EPA, you are in the US? Read your owners
manual or ask to see one at a dealer. The only thing they can charge you
for is diagnostic time, which I admit may be quite steep.
. CMPQwk 1.42-R2 . 763
----
+------------------------------------------------------------------------+
|Ye Olde Bailey BBS Zyxel 713-520-1569(V.32bis) USR 713-520-9566(V.34/FC)|
| Houston,Texas yob.com Home of alt.cosuard |
+------------------------------------------------------------------------+
-Bodnar,B.L.
>In article <DCDMs...@ssbunews.ih.att.com>,
> boh...@ihgp1.ih.att.com (-Bodnar,B.L.) wrote:..stuff..
>
>Ok...follow this.
>
>There is a cut in one of the plug boots. With new plugs, the arc occurs at the
>plug gap...as the gap widens the voltage required to fire the gap
>increases...eventually the voltage required to fire the plug is EXACTLY the
>same as required to arc through the break in the boot. The voltage at the
>working cylinders is exactly the same as the malfunctioning cylinder. You can
>not diagnose which cylinder is misfiring be measuring either voltage or
>current and both the voltage and current are exactly the same between the
>functioning and malfunctioning cylinder.
>
This is correct -- strictly monitoring the amplitude of the waveform on the
primary side of the coil will not allow one to detect the fault you have
described.
Stated succinctly: IDM's fault coverage is less than unity. But, then, I
never stated that it was...nor did I imply this...nor did I give you
information which would allow you to infer this.
>
>The functioning ones might require 30KV to arc the gap but the malfunctioning
>cylinder is arcing the boot at 30KV. There is no way to tell. If the arc is
>occuring somewhere along the wire where it has been abraded there may be
>little visual spark...just a little twinkle. The current will be the same as
>well due to the conservation of energy rules all of the coil packs stored the
>same energy (more or less) so if they arc at the same voltage the secondary
>current will be the same. The reflected sense pulse will appear identical at
>all of the coil packs. All the system can tell is if one cylinder is arching
>at a DIFFERENT voltage...not where the arc is occuring...in this case...the
>arc voltage is close enough to the others to be within the window and is not
>detected as an error.
>
>George Bonser
>gr...@cris.com
>
I disagree with some of the stuff in this last paragraph. Kindly relegate
followups to e-mail (unless there are other readers who are interested in this
topic).
Regards,
Bohdan Bodnar
Andy Dingley
>The combustion
>chamber and sparkplug merely form a gas diode (non-linear load)
It is *not* a simple negative impedance gas arc. The pressure changes
inside a combustion chamber have a dramatic effect on the impedance
behaviour wrt. time.
--
Andy Dingley din...@codesmth.demon.co.uk
If all it takes is an infinite number of monkeys with typewriters,
how come AOL haven't written any Shakespeare yet ?
Greg Marciniak
|> I have a 1992 F-150 with the 4.9L I-6 engine that has started to periodically light the Check Engine Light. The KOEO check shows
|> OK (111), as does the KOER check. A 172 (lean) code is stored in continuous memory. Ford replaced the oxygen sensor,but
|> won't do anything else under the emissions warranty. The Check Engine Light seems to come on after approximately 30 minutes
|> of driving and it can either be at highway speeds or while driving slow. There are no noticeable changes in how the truck drives,
|> but the gas mileage seems lower than previous and the exhaust pipe is black indicating that it is running rich. I have removed the
|> connector from the EEC-IV and checked the pins of the connector (all OK) and have done the same with the connector that is
|> between the engine and the large cable that runs under/through the fuse box on the wheel well. The engine coolant temp sensor
|> and the air charge temp sensor both have the correct resistance.
|>
|> Can anyone suggest what to try next? I assume that something is causing the EEC-IV to think that the engine is running lean,
|> then the EEC-IV is trying to make it richer (why the exhaust pipe is black and the mileage is down). It sounds like the oxygen
|> sensor, but it is new! Maybe the next step is to measure the oxy sensor output with a high resistance voltmeter and see what
|> the output is running.
|>
|> Fred
|>
I am not sure of the current status of the MAP sensor but they can cause
a rich condition too. I think that the computer defaults to a rich condition
in lieu of a correct input. I had this problem on an 84 F-150.
Greg Marciniak
Dave Hinrichsen - I-Net - 713-480-7488
>> I disagree with some of the stuff in this last paragraph. Kindly relegate
>> followups to e-mail (unless there are other readers who are interested in this
>> topic).
I've been interested in the topic, and would be happy to see the thread
remain public.
Dave Hinrichsen - I-Net - 713-483-0985
Software Technology Lab - NASA/Johnson Space Center
j...@gothamcity.jsc.nasa.gov