Conference vmsnet::car$note:carbuffs

   I have a 93 Taurus Wagon with a 3.8L V6. It has 67K miles on it and
   is well maintained. Recently we have started to experience minor engine
   problems. Here are the symptoms:

	(a) The Engine Check light comes on under load and then goes
	    off ~10 seconds after load goes down. For example, if you
	    accelerate hard or the family and gear is loaded and you
	    hit a slight slope on the expressway.

	(b) When the engine is warm and you come to a stop, say after
	    taking an expressway exit and ending at a red light, the
	    idle can be high (1500rpm in D and 2000rpm in P) and in
	    some cases the car engine just shuts itself off. If you
	    manually shut off the car when at high idle and immediately
	    start again, the idle can drop down to 1000rpm all by itself.

   I have not noticed anything unusual with the fuel consumption. Overall,
   it behaves well. The plugs are recent, so is filter and distributor cap.
   I almost get the impression that some sensor is not functioning. Perhaps
   something related to the emissions system has become mal adjusted.

   I would really like to fix it myself. Any ideas what could be wrong?

   Thanks for your help,

   >Per

First you have to dump the trouble code(s) from the ECU, then fix the problem,
then reboot the ECU.  You must have a shop manual to do it.  There is no
other way.

Jim

Re: .31

I have a '93 Taurus with the 3.8L.

I had the identical "check engine" light symptoms and I took it into Ford a couple
of times to try and find the problem.  They told me that my system had no memory
and it could not find out what the problem was (or what sensor had triggered) if
the light had gone back out.  They said they could only trouble shoot it effectively
if the light remained lit.  Mine never did, so they never found a problem.  I've
driven the car for 70000 more miles since the first onset of the problem (50000
was the initial problem -- I now have over 120000) and I'm still ignoring the light.
It's not very satisfying, but much cheaper than paying Ford to ignore the problem
for me.



								Dan

in re .33:

Actually, we saw inclings of this problem a long time ago and asked the dealer
to take a look. And just like in your case, there was no information available
in the car when it got to the dealer for them to determine any cause. The light
never sticks, just comes on and then goes off. The duration depends on how long
you are ''loading'' the car.

Does anyone know how many sensors are part of this cars "engine" assembly?
Specifically, which sensors could contribute to the light, at all. Given
that the problem appear to be exhaust temperature related or mixture related,
there cannot be many of them, can there?

What about the catalytic converter? Are there any sensors on that plumbing?
At 67K we ought to have expired the cat warranty too, so could the problem
not also be the need to replace the exhaust system? Have you replaced yours?

>Per

    
    >per  You have all the symptoms of a partially plugged catalytic
    converter (no solid codes), but the only way to know is with a pressure
    test. The universal Ford spec is 1.5-1.75 P.S.I. if its above that the
    cat is bad.  When I test them I drill a hole in the pipe between the
    exhaust manifold and the cat and shove in my cone adapter hooked to a
    pressure gauge. The reading is taken at idle speed. If its above the
    spec, the cat is bad. Then I zap the hole shut with the mig welder.
    
    -john

Per>
	I replaced the entire exhaust system on my Taurus early on
(maybe 40000 miles).  I can't remember if I had ever seen the 
"check engine" light problem before that.  The exhaust system is 
stainless steel and should "never" need to be replaced, but mine did.
The parts guy couldn't even tell me what one cost when I called him, 
because he had never run across the request before.  I'm pretty sure
the cat was replaced as part of that job.  I don't think it's relevant
to the discussion, though, because all of my problems have occurred 
since then.
	Also, when I asked about the light problem, the service manager
told me that there were 5 or 6 sensors that could trigger the problem, 
so he didn't want to simply "point and shoot" to try to trouble shoot
it.  
					FWIW,
						Dan  

It could also be a bad oxygen sensor.

Jim

    It's the oxygen sensor.  This thing is constantly checking for
    rich/lean mixture, apparently it isn't cycling or doing what's known
    as cross-counts often enough.  When you get off the freeway the sensor
    is slow to richen the mixture, so the engine stalls.  When you refire
    the engine it "remembers" how to run properly.  
    
    When you stomp on the engine and go uphill, the engine is slow to
    figure out it needs to be richened, so the idiot light comes on.
    
    The o2 sensor is cheap and easy to replace.  under $20.  Beat's going
    to the garage and getting jacked around, plus it'll probably fix the
    problem.
    
    Regards,
    MadMike

Thank you all for your help. I am going to try to replace the oxygen
sensor first and move on from there. I will post any progress here.

Cheers,

>Per

    I assume the engine is fuel injected, if so, everything is
    electronically controlled.  The sensors are many, but since the
    problem is sporatic and reproducable under certain conditions, it
    points at the O2 sensor.  This is the heart of the fuel delivery system.
    on a carbureted car, it'll use a o2 sensor and a Mixture control 
    solenoid. On FI, the O2 sensor continuously monitors exhaust
    temperature and the ECM continuously adjusts fuel delivery to the
    injector(s) based on engine demand.
    
    There are other sensors and switches to be aware of, but none that
    i'd finger right off the bat, since the idiot code is not stored, and
    the problem happens predicably.  There are temperature switches,
    Manifold Pressure switches and throttle position sensors, but I would
    think if any of these were busted, your car would run like crap 100%
    of the time.  There is also a solenoid in the transmission which
    controls clutch lockup.  These are a few of the sensors you may have.
    
    MadMike
                                       

    i "think" i saw were this ox sensor is located. on a taurus, if you
    remove the shroud around the fan, and look down to the header comming
    off the block, you should see a sensor on the pipe with wires comming
    out of it. probably should hit it with liquid wrench and let it sit
    overnight if it does not come loose first thing. 
    
    BTW. if this is NOT the sensor i think it is then someone let me know,
    since i'm considering replacing my ox sensor for the same types of
    problems...
    
    jim

    Yes, the oxygen sensor is located in the exhaust pipe, or towards the
    bottom of the exhaust manifold or header.  It has (usually) one wire
    coming out of it that runs to the ECM.  Hit it with some liquid
    wrench, and another tip to remove it is to allow the engine to be
    WARM.  Not hot, but warm.  This will make it easier to remove than
    if it's cold.  Another thing you may have a problem with (like I did)
    is getting leverage on the sensor.  I couldn't get a wrench in there
    and be able to turn it without removing the fan.  This was on a 
    cavalier.  Hopefully you'll be able to get some leverage on it.
    Disconnect the wire from the ECM harness and slide a box end wrench
    onto the thing and have at it.
    
    MadMike

    89 Ford Tempo 6cyl
    What's the recommended milage for a timing belt change? 

    
    	238.171 doesn't seem to list a belt for the V6.
    

    I'm asleep. Wrong note. The Tempo is a 4 cyl.

    
    	No recommended change interval.
    
    	However, it'll still strand you if it breaks, so this doesn't mean
    	that it would hurt to have it checked out.
    

After shopping around, I ended up buying two (Bosch) oxygen sensors from VIP
auto in Merrimack. They were on sale and charged $39.99 a piece. I also bought
a special socket (1/2 wrench mount) to remove it -- the special socket works
with any oxygen sensor and has a slit along one side allowing the wires to come
out while you turn.

Both sensors are best accessed from under the car. The front one was a breeze.
It took me like 2-3 minutes to replace. The rear one took over an hour, because
it is located in such a bad spot. I had to use a universal with the socket. The
worst was that the wires kept getting wrapped around the socket and then jamming
against the engine, making it really tricky to untangle. I ended up snapping one
of the four wires as a result of this, very near the sensor and by that time I
almost had it screwed in. So I had to take it all back out again and fix the
wire and do it again. I also managed to damage the threads on that rear one and
had to take things out again and fix that. A real bear, to say the least. 

But the results are good! The car no longer stalls.

Thanks for your help,

>Per

Oh, one more thing. I was advised by VIP to disconnect the battery after having
replaced these sensors. The reason was to make the ECM recalibrate itself with
the new sensors.

>Per