More of a generic question, but it would help me decide if I want to
let Ford have at my Taurus, or just drive it to the damn scrap yard
and get this over with.
I have an OBD1 scanner (93 taurus) and in the past, it has given me a
few codes that have helped with problems so I know it works, and I
guess I can say that I know how to run the tests. At the moment, with
my high engine speed problem, it shows no codes at all.
All I have to go on with this statement, is that it is what folks have
told me, and that statement is that Ford dealer scanners can access
codes that are not revealed by the $100 scanner that I am using. I
have heard yes and no, but some are adamant that they can retrieve
information that I cannot.
As it is, I have no codes to go on. If Ford can dig out more, and
useful ones, then maybe I have to bite the bullet, but if I am going
to pay them $100 just to read the computer and come up with no codes,
that doesn't seem like the right way to go.
Anyone have any insight or comments? Are there "hidden codes" in the
OBD1 computer that only Ford can view?
I had an idle problem with a 95 5.8 liter. It is also OBD 1. I
couldn't find any codes, and I finally took it to a Ford dealer. The
guy spent 45 minutes trying to diagnose the problem, and I went back
into the service bay with him. He couldn't find any codes either. He
told me all he could do was hook it up to a "box" that would be in
between the EEC and all the sensors. That way he could check each
sensor, and decide if it was a sensor, a short somewhere, or the EEC.
He wanted me to leave it for at least 2 days. The open-ended bill
would start at $300. As my vehicle was driveable, I didn't take him
up on the offer.
What kind of scanner do you have, and is it available, or some kind of
special fordo device?
I only have the code reader, that does KoffEngineOff and KonEngineon
tests, plus clearing existing codes.
Given how much it would cost to leave this up to Ford, a good scanner
might be a better investment for long term.
That would be a "breakout box"
you connect it between the car and the computer. It lets you easiely probe
all the computer wires to check resistance, voltage, ect.
A Ford sevice manual will quite often say "connect breakout box" somewhere
in the diagnostics.
Just so you know, with the service manual, basic electrical knowlege, and
following the book exactly you CAN/WILL fix it.
It is possible to not have a breakout box when it asks for it but you have
to probe wires and figure out which wire is which.
Also, a visual check is always asked for first. Don't overlook the obvious
like a broken vacuum line, blown fuse, stuck throttle cable.....
The Ford shop manual I have covers every detail imaginable, but it
doesn't address the idle/emissions circuits beyond basic, 'this is
what it is'
Instead, it refers me to the Emissions Manual, which I can only find
in one place, for $250! I keep searching ebay, had one guy say he had
one for $10, but he disappeared, so I am without the technical
information I need.
I agree, its not hard to test the circuits, sensors, and voltage
levels, but no knowing what is 'normal' makes it more of a crapshoot
than anything else. I usually connect up a 'harness' of wires that I
bring into the interior, so I can monitor the suspected devices and
sensor with the appropriate meter. What I don't have is, the voltage
to expect at idle, from the TPS, or what the IAC levels should be on a
proper running engine. Its the details that seem to be lacking in the
places I have looked.
My idle issue seems unique, in that it is normal when driving low
speed around town, but out on the road, going 50, when come to a stop,
the engine is idling way too high, making it hard to even get it to
stop. Shut off the engine and restart it, and its all back to okay,
till the next time I drive 40-50mph......
That's my story :-)
Thanks Scott. If you know anything more technical, or of a place that
might have numbers and details, I would sure like to hear about them.
When the idle is high like that, if you reach your toe under the accelerator
pedal and pull up, does the idle drop? I had a similar problem on my '89
Probe, and found the problem was with the linkage for my speed control
(cruise control). After all the electronic and electrical tests I did, it
turned out to be mechanical.
The linkage is good. I have scrubbed the throttle body. When the idle
is up high, I can open the hood and push the throttle manually, and it
is positively as closed as it can be.
I would kill for the easy way out :-)
Ouch! That is pretty much the way I expect to be treated if I ask them
to fix my problem. They have a lot of nerve, but then, the way I see
it, they don't want to do these kinds of jobs, and prefer the 'by the
book' problems where its easier, and they can make plenty of margin on
Thanks, and I hope you are able to figure out your issues yourself.
I've started out to reply to this train of thought several times.....
nothing comes out sounding quite right.....
Bottom line.... I fix these kinds of things as part of my job. I am blessed
with a very good understanding of electricity and practice, training and
experience have helped hone my skills.... When others can't fix an
electrical concern, they bring it to the overpriced asshole... The sad truth
is that they could have saved a lot of money, a lot of time and a lot of
frustration if they'd just brought it to the overpriced asshole first.
Automotive electrical will separate the men from the boys... just having the
tools and manuals (that do cost a lot of money) does not gaurranty that
there is anyone available that knows how to use them to their best
The boy cannot be a man without the details of the electrical system.
I am overqualified for automotive electronics repair, based on my
career, but without information on what happens when, what the levels
should be, and where to look for them, there is little that even the
genius can do.
If I hand someone one of my electronics designs that is not working,
sans any documentation at all, they are not gonna be able to repair
it. :-) That is where I am at with this car at the moment. $300+ is a
lot for the proper manual, and since there are no codes in the ECU, I
doubt there would be much in there that could help.
Okay, I will repair it, but its gonna take a helluva a long time, and
a ridiculous amount of effort :-)
There is not going to be any "hiddin" codes on your 93. Some scanners can
see data and do tests that others cant.
93 is new enough for a good scanner to see data. Do you have a scanner or
"code reader" ? I guess it could be possible for a cheap code reader to not
work correctly or maybe not see memory codes.....Is it a high idle problem?
You have replaced the IAC? No vacuum leaks? Has anyone messed with the
minimum air adjustment? Is it possible that the computer thinks its in drive
or reverse when it isn't? Maybe it thinks the AC is on? You should get a
code for that one though. Does your scanner tell you to cycle the AC on and
off? Is the timing adjustable? Does it even have a distributor? Don't forget
you could have bought a bad IAC, wouldn't be the first time. Maybe the
computer thinks its cold when it isn't? That should give a code too because
it should be warmed up before the test. If all else fails I would try to set
the minimum air lower(or higher if its a slow idle problem) (and remember
how many turns you did so you can put it back where it was) just to try
it...Can you see the data for the IAC on your scanner? If so you should be
able to tell if the computer is trying to slow the idle down but it won't,
or the computer is holding it high for some reason (like it thinks the
engine is cold, thinks its in gear when it isn't, thinks the AC is on when
it's not, that kind of thing) It should give you a code for not being able
to controll the idle if there is a problem. Does it idle up and down when
you do the KOER test? It should. It could be a bad computer too. You could
also check the TPS, you should get a code for that but....If its supossed to
be like .6 volts at idle, then make sure it is. If I think of anything else
I'll post it. Good luck.
I am thinking a '93 will be EEC-IV - not OBD... my '93 Cougar is, anyway.
Except for being able to read codes while driving, I don't think the dealer
unit will do better than what you have. I'd look for mechanical stuff,
first. Stuck linkages or a cracked vacuum line... the EGR can get junk in
it after a highway drive and cause odd stuff. A vacuum leak can make a car
do very strange things... Also, you might have a gunked up throttle plate
or linkage. It wouldn't hurt to clean the IAC valve... they are supposed to
be closed while driving and open at idle to provide enough air for idle.
Might be opening too much or sticking...
Hope this is helpful...
I couldn't begin to know the difference between OBD1 and EEC-IV, other
than the stuff in the manual :-)
Since the problem can be cleared by turning the key off and on, I
don't believe its anything like a vacuum leak, or a mechanical issue.
New IAC, and new TPS
The throttle body and linkage are clean enough to eat off of :-)
I am desperate for information on electrical values, so I can try to
pinpoint what the computer is doing.....
Thanks a lot.
take a trip down to pep-boys or the like and take a look at their books. I
bet it will have at least some EEC 4 stuff.
Do you get any codes? Do the key on engine off first----fix codes. Then do
the key on engine running---fix those. Lower code numbers first.
Does your scanner tell you to cycle brake pedal, cycle AC, Go wide open
throttle(WOT) turn steering wheel one full turn? ANY of that stuff during
the key on engine running test? If not something is wrong.....Its been a
while but I think alot of the voltages, resistances, ect are the same on
those same years. If you have NO codes, It sure sounds like the IAC is
sticking. I would take it back and get another one. Tell them it worked for
a week then went goofy. It would not be the first time a new part was bad.
Or shoot some wd40 in it and see if it changes anything. Check ecm
connections under the hood, at least unplug, look for corrosion, and plug
back in.Look very closly at the ones near the battery(acid), be sure the do
the main harness at the ECM too. Someone mentioned the egr sticking but
that will usually set a code and give you the CEL (chk eng light). If you
had the emmisions book you could go to the rough idle part and have fun.
Take a look at those cheap chiltons books or ALLDATA online, or a manual on
DVD maybe? I have never used alldata online. I know the cd version is
good(look like the ford book scanned) Search the net for FORD EECIV too.
The TPS should be about .6 at idle and slowly go up to about 4.5v as you
open the throttle all the way. one off the wires going to it should be a 5
volt reference .
No codes. It cycles the sensors, fan, and other junk, asks for the
brake, the steering and WOT stuff as well. If I don't do one of them,
it does report it as a problem, so it works. Heck, I know it works, it
won't do anything if I leave one of the doors open :-) Took a while to
figure that one out.
Guess it couldn't hurt. I didn't consider it, since the symptoms are
virtually identical to the original one I replaced, but its worth a
I have been doing that. Probably no such thing as did them all, but I
am working up a "schematic" so I can better test what is available.
The resistance is linear. Still haven't checked the voltages. You
mentioning them are the first I have heard anything useful regarding a
The engine for my VW van is sitting on the garage floor, waiting for
someone to go put it back together and reinstall it. So many tasks, so
few "someones" :-)
That helps. Just chatting about stuff often stimulates the thought
I am guessing that since all the places I have brought this up have
not mentioned any control device or sensor beyond the IAC and TPS,
that there is probably no other place to look. I suppose that narrows
it down and helps simplify it.
I just cannot believe there are no codes :-(
With your electronics background, you could probably learn a
lot from a book called "Ford Electronic Fuel Injection" by
Probst. It goes thru the operation of the various
Ford/Mazda systems up thru EEC-IV. It also goes into each
sensor, how it works, how to check them and what values to
expect. It also has wiring diagrams for various models of
vehicles. It can be a complex system but, if you can begin
to look at and understand the components, it makes it much
easier to step back and look at the big picture to consider
what may be happening. I found a copy years ago at a Ford
Motorsport parts department. It was and may still be
available on Amazon. Once you see how the system works, it
is much easier to see how one component interacts with the
others. Most of the test procedires can be done with a good
DVOM. An analog meter can be helpful on a couple of things.
The MAP sensor can be checked with a DVOM but, you will need
something that can measure frequency since that is it's
communication with the ECM. If you work in electronics, I
am sure you have access to more complex instrumentation than
the EFI presents once you understand how it works and have
the expected values.
No. But there are faults that do not show on any computer diagnostic. For
those you need a man who knows what he is doing and be prepared for him to
slowly check things one by one. As you say it can be expensive.
John you may have resolved your problem by now but here are a couple if
web sites which are very educational for future reference:
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