I have been having trouble with my '93 Taurus not running smoothly when the car is travelling at an even speed. I wrote to this discussion and the feedback was that it’s likely my oxygen sensor. So I took the car to a backyard mechanic. He told me that the car has 4 sensors, two for each bank of cylinders, one in front of and one after the catalytic converter.
Two questions:
1) Is this true? I ask because my 1986 Mustang had only one sensor.
2) If there are four sensors, how do you find out/decide which sensor needs replacing?
Thanks for any help!
Before replacing sensors … CHECK THE STORED COMPUTER ERROR CODES (easy to do).
Both the 3.0L and 3.8L engine have 2 sensors.
Both sensors are the same, so I would replace the one closest to the engine first (easiest to get at). If that didn’t fix the problem I’d trade the one I removed for the other sensor (hard to get at).
I took a quick look at the factory wiring diagrams for my 95 Taurus & as Gary123 mentioned there are 2 O2 sensors. One in each bank.
As gary mentioned you need to pull the trouble codes b4 doing anything else.
Pulling the trouble codes is VERY simple to do.
See this link & find the connector thats mentioned. Most likely place is under the hood on the passenger side firewall.
Connect a 30 buck scanner to that plug and let the testing begin.
You don’t HAVE to use a scanner.
Find the test block (engine side of firewall on passenger side).
Use a jumper to connect Brown wire to the Gray/Red wire on test block.
Turn the ignition key to start (don’t crank).
Read the 3 digit codes from the flashing yellow CEL on dash.
Digits are flashed twice in groups of three.
See more info at
http://www.troublecodes.net/Ford/
Gentlemen,
Excellent information and advice all the way around. I can now proceed.
Thanks very much.
Best regards
I would be extremely surprised if the O2 sensors had anything at all to do with the current problem. The O2 sensor has to be the most whaled upon automotive part in the world.
There are a number of things that could cause this problem; failing fuel pump, fuel filter, clogged converter, misfire due to plugs or wires, vacuum leak, ignition timing off (easily done if the dist. has been dinked with), or even an ignition module problem since this car is one those infamous TFI-IV models.
Dear ok4450,
Hmmmmmmm…that’s a long list, and a good one to give me an idea of what it might be. I guess it’s even more crucial that I check the stored computer error codes to see what they say and then go on from there.
And can you please tell me why the TFI-IV models are “infamous”?
The Fords were infamous for bad head gaskets and transmissions.
Yeah, the ignition modules were troublesome to the point that there was a class action lawsuit which Ford lost.
The module is mounted at the base of the distributor & can cause a no start or engine runs fine cold stalls hot, or in my case at 140,000 miles my Ranger was backfiring something awful.
Pulled the trouble codes & replaced the module. Problem solved.
Heres another link with some more very simple testing that you can do that might help pin point your trouble.
http://www.users.bigpond.com/ergoff/vac1.htm
Checking fuel pressure is also very simple.
ONE OTHER SYMPTOM IS THAT THE PICKUP IS LOUSY ALTHOUGH UNDER ACCELERATION THE CAR DOES RUN SMOOTHLY. ONLY WHEN IT’S RUNNING AT AN EVEN MPH DOES THE STUTTER OCCUR. DOES THIS HELP NARROW THE PROBLEM?
Bad head gaskets and lousy transmissions, lousy ignition modules, and a class action suit. Yikes! Not a very good recommendation for a car
Thing is, I like my Taurus. It’s roomy and comfortable, it always starts, the radio and AC are great, it has a huge trunk. And my particular car has purple-shaded windows, which makes it look somewhat cool.
Were the problems fixed by Ford later? Is a later year with the same body style a better car? If so, maybe I could try to find one with lower mileage. I like the boxy style. The round model that looks entirely different I don’t really care for. Were they better mechanically as cars the round body style? Or did they have their problems too? Is there some year and model of the Taurus that is considered superior where Ford ironed out all the kinks and the cars were sound and reliable?
Also. were the front struts notoriously bad? Mine are, but the car has 114,000 on it.
Finally, someone told me that the 3.0 was a better engine than the 3.8, that the 3.8 had mechanical problems that the 3.0 did not have and consequently when buying a used Taurus it is better to avoid the 3.8. Anybody know about this?
Really very much appreciate everyone’s info/feedback.
I own cars with both engines and had to replace head gaskets on both … but only after 150K miles (each). It’s my contention that the engines don’t like heat so I now run them around 160F (bottom mark on temperature gauge). I have never had a transmission problem on either car (I attribute their longevity to running cool).
I like the 3.8L engine. It has a lot more torque than the 3.0L although it’s rated at about the same horsepower. The statement that the 3.0L is a “better” engine is usually made by sellers trying to get rid of their 3.0L cars.
I like my old Ford’s, I’d drive them anywhere … once these cars reach 15 to 20 years in age, I don’t think they have any more troubles than other old cars.
Actually, a stutter like this at an even speed can be caused by a fault in the secondary ignition; plugs, wires, cap, etc.
Just for hoots, you might remove the coil wire and make sure the coil wire ends are clean and the dist. cap and coil terminals are also clean.
I mention this because someone brought me a Ford one time that had a stutter like this. The car would start right up, hot or cold, idle like a sewing machine, and accelerate like a dream. At a steady speed it had symptoms similar to running out of gas. The problem? The coil wire terminal in the dist. cap was corroded. New coil wire, ran a dist. brush through the cap, and problem solved.
Not all of the 3.8 engines are bad. It’s just that sometimes faults happen and a unit gets tagged with an unreliable badge. Several neighbors have owned 3.8 Tauri (plural 
)and put a couple or 300k miles on them with no hiccups.
That being said, I prefer the 3.0; it’s pretty much bulletproof.
Some of the early models were prone to transmission failures but changing the fluid/filter at 30k mile intervals usually heads these problems off.
The trans in my old 87 Sable had about 385k miles on it when I sold the car and it was still shifting fine.
As to the ignition module, testing them is pretty much a waste of time. They can test fine and still fail on an erratic basis. They may also not leave any codes stored in memory. Hope that helps.
Once again, friends, I am in your debt.
ok4550: I will try your suggested trick with the coil wire this weekend. Will let you know if it worked.
Funny thing: After writing that note about the round version of the Taurus, I saw one today that looked great. Silver with a sunroof. The only trick it had were some nice rims, though they were not pimp style, just good looking silver with five spokes. That car made me change my mind about the later model. Might try to find one in excellent condition. Was the engine the same as the boxy one?
Dear ok4550
Wow! Fantastic!
Pulled wire from coil end and a small avalanche of grey-white ash/particles poured out. Inside the wire, the terminal was, of course, thoroughly corroded. Also checked the rotor and distributor cap at the same time. Rotor contact was pitted and corroded and contacts inside distributor cap were all worn. Seems like somewhat of a testimony to the durability of the engine that it was even running considering the poor condition of this part of the ignition.
I replaced wire, rotor, cap.
The car definitely runs better. The pickup/power is much improved. Most of the stutter at an even mph is gone, although it is still slightly present. The engine also idles roughly at low rpm. This is very noticeable when sitting at a stoplight in DRIVE. If I shift to NEUTRAL, i.e., take the load off the engine, then the idle smoothes out.
I figure to next remove all the plugs and check them. Any advice after I do that as a next step if the rough idle and stutter are not 100% eliminated by plug replacement?
Again thanks for all your help.
I just replaced the plugs and plug wires on my 1993 3.0 V6 Taurus because it was still running a bit roughly after I had replaced the coil wire and distributor cap.
The car runs worse now after replacing the wires and plugs than it did before! Way worse!
I think I have inadvertently mixed up the plug wires on the distributor cap so the firing order is off. I tried switching the two wires that I thought I may have mixed up, but this made little difference. It still runs very roughly and the power is, of course, pathetic.
Can someone please explain the correct plug/cylinder wires for each bank vis-a-vis their correct placement on the cap so that I can check to see if I have it right. I can plainly see the “1” stamped on the cap, so that will give me a place to start.
BTW: I set the gap at .044 because the clerk at Autozone said that was correct. I bought new Ford plugs. Can someone confirm that this is the correct gap?
This is almost completely edited. When I posted a few minutes ago I could not find the info in my Haynes Manual for '86 thru '95 (Chapter 1 says “do them one at a time or label them carefully, or else you will confuse them and the car will run bad”) But now I found some info in Chapter 2B on the 6-cyl. You can dope it out from this:
Firing order is 1-4-2-5-3-6
Cyls 1-2-3 are the rear bank (toward firewall), from passenger side to driver’s side. Cyls 4-5-6 are the forward bank (toward front of car). Distributor has Cyl 1 marked, as you observed; distributor turns clockwise on the 3.0L V6 (CCW on the 3.8L), looking from top.
If that doesn’t work, and if nobody else has advice here, finding another Taurus of similar vintage with the same engine should be pretty easy. Then you can copy that one.
BTW, here are some useful quotes from the book:
“Warning: The electric cooling fan on these models can activate at any time, even whin the ignition is in the Off position. Disconnect the negative batery cable or the fan motor when working in the vicinity of the fan,”
“Note: Every time a spark plug wire is detached from a spark plug, the distributor, or the coil, silicone dielectric compound (a white grease available at auto parts stores) must be applied inside each boot before reconnection. Use a small screwdriver to coat the entire inside surface of each boot with a thin layer of the compound.”
They also say to apply the dielectric grease to the distributor rotor, but NOT to the electrical contact leaf/button.
I guess you already know about pulling on the spark plug boot – NOT on the wire – with a twisting/pulling motion.
Haynes recommends a torque wrench for installing the spark plugs; 6 to 10 ft-lb.
BTW I’d say the fact that it ran the same after swapping two plug wires indicates that either the plug wires are WAY mixed up, or maybe there is something else going on. Did you maybe knock something else loose? (Another use for finding a copy-me Taurus.)
Firing order is 1-4-2-5-3-6 (both 3.0L and 3.8L engines).
Looking at the engine from the passenger side …
Cylinders are numbered (front to back) 1-2-3 on left and 4-5-6 on right.
Darn, but thanks for trying. I was going to buy a Haynes manual to see if I could work from it, but from what you say there’s no point.
The thing is that I am almost certain that I have the front bank of cylinders correctly connected. I did them first and followed the principle of doing them one at a time. When doing the second (rear) bank I accidentally pulled a wire from that bank that I had already replaced, and then I got confused as to which wire went where. It seemed to me that there were only two choices so I tried swapping them but as I say the engine runs roughly either way. This is extremely frustrating! I wish I’d left the wires alone, but now of course I am stuck with trying to figure out what’s wrong.
One thing: Does your Haynes say whether the plug gap should be .044 as the Autozone clerk told me?
I do know now from another e-mail to me that the two banks are numbered 1-2-3 and 4-5-6 beginning at the passenger side and moving toward the driver side. If someone could tell me where each position for the cylinders is on the distributor cap then I could figure out how to wire the plugs properly.
Ok, thanks, I now know the cylinder numbers for both banks and the firing order. Great.
All I need to know is the cylinder number of each terminal on the distributor cap and I should be able to work from there. I can see the large “1” that’s embossed on the cap at about “4 o’clock”. Can anyone tell me the cylinder number for each cap terminal in succession working, say, clockwise from the “1”.?
I was editing my 10:34 PM post, above, while the other posts were coming in. See there.
After Cyl 1, next clockwise is #4, then #2, etc.