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Okay before I start, you'll obviously be able to tell by how much detail I give that I am a female haha.

I own a '96 Mercury Mystique LS 2.5L V6 Engine..had it since '07 when I started university. We have a Love/Hate relationship..meaning I have a LOT of memories w/ this car and even though it's let me down on a few occasions, I have to fix this. Yesterday, I was driving and just like when the power in a house goes out...my car shut down in the middle of a busy intersection. Right before it shut down, the RPM meter was going back and forth like crazy...my car was julting [if that makes sense] and the MPH meter shot up to about 80..when I was stopped because of the traffic. The airbag light came on, the ABS light, Traction control [pretty much only the YELLOW lights]. Once it flickered back to life, I pulled into the nearest gas station and left it there. I had a new alternator put in about a month ago..a new battery 2.5 months ago. I've had a major tune-up two years ago..just had new brakes/rotors put on both front AND back and four new tires. My Check Engine light is always on..I've had the code pulled by multiple locations and they say it's the O2 sensors. I've had those replaced about 3-4 times..then contacted Mercury dealership...apparently that is a feature that is known to accompany Mystiques...almost like a false positive.

I'm coming to this forum because I'm tired of coughing up thousands of dollars at different auto shops just for them to check it out and charge me outlandish prices and taking advantage of the fact that I'm a female. I know I'll need some serious cash for this, but I want opinions first. Please help, and thanks in advance..  

these kinds of problems can be really tough to solve....

i actually need to work on one like this right now... so expect a LOT more later this evening..

a few things.. just because the trouble codes say... oxygen sensor... does NOT mean the oxygen sensors are bad... what.. its says the oxygen sensor signals to the ECM are not what the ECM is expecting to see..

vacuum leaks are a MAJOR cause of oxygen sensor codes...   softened vacuum hoses collapse with the vacuum and leak air into the system..     leaking intake manifold gaskets are also a cause...   since your car is an OBD2 car...  you can plug in a OBD2 scan toll and look at the wave forms from the oxygen sensors..   with some reading up .. you could see if the wave forms are as expected...

you could also look at the short term fuel trim.. and the long term fuel trim.. if the car is running good.. the fuel trim will be within a few percentage points of 0...   within 10 points.. usually..   i had one come in with it a -100.. said i bet there is a vacuum leak.. opened the hood and there it was...

but.. this won't cut off your car...  

do you have a digital volt meter...  if so,.. start the engine.. turn on the headlights...

set digital volt meter to 20 volts DC scale..

1.  test between the Positive and the Negative battery posts...  14.1 to 14.8 volts is expected...

2. test between the Negative battery post and the engine block...   0.04 volts  is expected..

3. test between the Negative battery post and the body of the car.. 0.02 volts is expected..

4. test between the engine block and the body of the car..    0.02 volts is expected...

for tests 2.3 4.  you might have to change the meter scale to 2 volts DC..

digital volt meters start at 7 bucks and you usually don't need to spend more than about 25.. there are some 15 buck meters that do just fine..


post your results..  by number...

this is the first part of several tests...  called a voltage drop test...   if there is current flowing between the parts. as would be expected when the engine is running and the headlights are on..   if there is corrosion in the circuit.. you will measure more than the tiny voltage amounts i posted..

this is a critical test for fuel injected cars...   since electrons flow from negative to positive..  any resistance will cause different parts to have different amounts of voltage.. and that can be enough to shut off the engine..


there could be loose fuses.. dirty relay contacts.. bad ignition switches..   i seem to recall that happening on that model .. but i could be wrong...

tools to buy.. .

digital volt meter..  under 25 bucks.. try to select one with a 20 AMP DC setting..  or more.. as you might need that later..

circuit test light.. under 20 bucks for a good one..  

you will eventually need an OBD2 scan tool that displays live data.. do you have a harbor freight store near by??   the 98614 will do most of what you need..  yep.. they cost just over 120 bucks.. but thats about one trip to the dealer...

there are laws also .. in some states. that require the service writers to scan for codes..  write them on the service order so you have a copy..  so they don't just turn out the light and charge you again and again for the same problem.. or do this till you are out of the manufacturers or emissions warrantee where you have to pay for it..  

find a shop that knows what there doin.The o2 sensors go in them all the time,and if they use the cheep ones which most shops do they holes are in the wrong location and will turn the check engine light on.Not saying this is your problem, but could be y your getting the o2 sensor codes.you need to talk to a bunch of people to find some one that knows a person that knows what there doin!