Solving a Misfire in a Sable/Taurus...

LEDAdd1ct

Flashlight Enthusiast
Joined
Jul 4, 2007
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Hudson Valley
I have a problem with my car which is driving me bonkers, and I am hoping someone here can assist. The story goes like this:

A few years ago, my "Service Engine Soon" light in my 1999 DOHC Mercury Sable (Taurus) came on. I was told it wasn't a serious issue, and let it go for awhile. When I was able, I had all the plugs and wires changed, and the technician turned the light off. However, miles later, it came on again. The code was the same, "Cylinder Six Misfire." I used the computer from Autozone to read the code and turn it off, and it went away for some time.

Recently, it came on again, same Cylinder Six Misfire, but I noticed over a period of months that the car was shaking with a rough idle. When you drive, when you accelerate, you don't feel it at all, but when you are sitting still, you definitely do. I brought it in to a local branch of a national chain of auto repair shops, and they diagnosed it as a bad coil pack. They swapped the coil pack, but told me that there seemed to be a lot of carbon buildup in cylinder six, and though the new coil pack would make it fire, it still wouldn't be 100%. They advised me to go for a long drive over the weekend.

A couple weeks ago, I did a 250 mile loop, with the "Service Engine Soon" light still on. I added fuel injector cleaner prior to the drive, in the hopes of removing the carbon buildup in the cylinder. However, the car still idled rough, and when I paused during the trip to snap some photos, the tachometer fell low and the car almost felt like it would stall out.

I brought it back, and they did some rerouting to isolate the cause, pointing spark plugs to different places. They said that the plugs and fuel injectors were working properly, and that since the code was reappearing on cylinder six, it was probably just dirty.

I do not know if this is related, but when I drive, there is a ticking noise coming from the bottom left. The mechanic said he didn't see anything odd from the bottom of the vehicle. When I drive faster, the ticking increases. It is never present when I stop, as the frequency of the tick follows the velocity of the car, and goes away whenever I apply the brake. When I brake, the ticking vanishes. The last time I was in, the mechanic told me that when I use a computer at Autozone, it reports a code that is already there, while their more advanced computer can read data while the car is running. He said the reason the "Service Engine Soon" light didn't turn on is because while it was still misfiring, it hadn't reached the level of being serious enough to reactivate the light. This evening, with my gas running low, the "Service Engine Soon" light once more illuminated. I have no doubt that when read, it will indicate, once again, "Cylinder Six Misfire."

At this point, I don't know what to do. While I can assemble a computer and know a little bit about flashlights, my knowledge of cars is lacking. I have a new coil pack, which may have reduced the issue, but the shaky idle is still there. When I am at rest, I can see the car's incandescent lights gently throbbing on the wall. So, 1999 DOHC Mercury Sable, 126,000 miles, plugs and wires changed, new coil pack, persistent cylinder six misfire. I googled vacuum leaks, but the articles I pulled up state that a vacuum leak would impact all the cylinders, not simply one. I am not in a position to continuously drop money into solving this, but I have found the members of this forum to possess a depth of knowledge that often exceeds that of the average man or woman on the street. My dad has a Taurus wagon of a similar vintage with 150,000+ miles, and it does not shake when idle or stopped.

I would appreciate any constructive advice. Googling returns a thousand possibilities.

If there is any other information I can supply, I will happily oblige. There are things that may seem obvious to persons in this field which I would never consider.

Thank you!
 
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I'm in awe that you got a Sable to run over 100,000 miles; that said, check for air leaks on the intake side, if that's not it then it's probably not going to be a do-it-yourself problem unless you're experienced with changing valves/rings. Throbbing lights means the battery needs to be replaced. Ticking that matches your speed is usually something stupid like a rock in the wheel assembly, which won't harm anything.
 
A compression check may be in order. A sticky or burned valve might account for it, and that will show up with a compression leak down test.

I did a quick google for "taurus Cylinder Six Misfire" and found a lot of discussion about that symptom. Replacing the "pre cat" 02 sensors on high mileage cars was recommended in one thread.

In the old days I'd look at all 6 plugs to see that they were the right color and the electrodes in good condition and properly gapped. I have not looked at a sparkplug in the last decade. :)

Daniel
 
I agree with doing a compression check. Assuming that's good, then I would suspect clogged egr ports.

Could be all or most of the ports are clogged, but that the port for cyl 6 is open, and when the egr opens cyl 6 gets all the exhaust gases causing it to be too lean and causing a missfire in that cyl.
You could try a seafoam treatment, it might help.... maybe. But I've seen photos of ports so clogged that an ice pick was needed to clear them.
 
If you have an advanced scan tool, go into " freeze frame " and note the engine temperature when the code set.
If coolant temperature was less than 170 degrees, suspect the plenum gasket. They are rubber and harden up from heat and will no longer seal at low temperatures. A common problem.
 
Thank you all for the replies.

When I am able, I will pop by Autozone and get the codes read and printed.

So far we have:

1) Air leaks
2) Compression Leak
3) Bad oxygen sensor
4) Clogged EGR port (what does EGR stand for?)
5) Dried out plenum gasket

The headlights throb because the car is shaky when still; near as I can tell, their movement is purely mechanical in nature.
 
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Your running on 5 cylinders =

If it were my car,, I'd do a strong Seafoam treatment in the gas.
Then a compression test if needed.

If a compression test shows difference on cylinder 6, you have to ask yourself if you really want a rebuild on a '99
 
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Regarding seafoam, read the instructions, I believe half goes in through a vacuum line, and the other half goes in the tank with about 4-5 gallons... again check, and read the instructions.

IMO if it were a vacuum leak, you'd probably also get a bank 2 O2 sensor 1 lean code.
Where-ever it was that you read "bad O2 sensor".... they were wrong (at least for YOUR problem)
 
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Your running on 5 cylinders =

If it were my car,, I'd do a strong Seafoam treatment in the gas.

+1 on the sea foam, buy a can and throw er in your gas tank. be sure to put it in on a half a tank, shake the car a little bit, then finish filling er up. be sure to run the car awhile and DON'T fill it up because if you do, you'll water the treatment, so run it down kinda far (not far enough to burn up the fuel pump, just let it go down a little bit past half tank)

If i recall correctly, you can put seafoam in the oil but you can't run it very far without changing it.

seafoam is on sale in my area from advance auto for 7.99, not sure if that is nationwide sale or local, but it's worth a short by saving a few bucks, cause it normally runs about 10.99 in other stores.

you can also check to see if a cylinder is firing. run the vehicle and pull the wire off each plug (try not to get shocked wear rubber gloves) and if the motor dies down when you pull it off, then that one is firing good. If you pull the plug and it doesn't die down, then you have trouble there.

About the clicking, a neighbors vehicle used to do that same thing, and it turned out to be a loose clip in the brakes or a loose caliper.


I'm not much of a mechanic, but hope you find something i said useful.


you may not want to take my final advice,

but my motto is, if you can fix it, run er till she blows.
 
If i recall correctly, you can put seafoam in the oil but you can't run it very far without changing it.


you may not want to take my final advice,

Again... READ THE INSTRUCTIONS!@!!!
jonzo @ fordforumsonline.com claims he burnt up his engine after putting seafoam IN HIS OIL .

To answer your question... what does EGR stand for, its "exhaust gas recirculation"

Another possible missfire cause, could be a clogged/sticking fuel injector a seafoam treatment MAY help that.
 
you need to find good diagnostic shop, guess swapping parts is a lot more expencive than diagnostic fee.
i have worked as a auto mechanic, and seen ppl spend thousands on parts trying to guess what was the problem, even thou i do have some experience in fixing cars, i would not even try to guess without the car right in front of me.
in a car that is 14 years old, anything is possible, bad gasket, clogged egr, cracked vaccum hose, loose contact......etc. wish i could guess, but it needs good diagnostic shop, and someone that knows what he is doing, btw dealers shop would be the last place, in general, not only they will charge you at least few hunddreds for testing, but they would still charge you even if they don't find anything, plus ppl that work there, are not garranteed to know stuff better than any other shop. have dealt with dealers before.
 
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Do a strong* Seafoam with like 1/2 tank gas... just add to the gas.


*around 2~3oz. per gallon



^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
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Found my un opened can today in the building. it says you can put it in the oil, but i've heard lots of bad stuff about doing it. I think it comes from people putting to much in, and running it to long, cause you can't run it that long, you are supposed to do it just before you change your oil.

also

be VERY VERY VERY careful when putting it in the vacuum line that leads to the cylinders, if you pour it to fast, you can HYDRO-LOCK your engine. many videos about it on youtube. i just use seafoam by putting it in the gas tank. also stabil ethanol treatment seems to be pretty good from what i hear on a tune up for vehicles. I ran some stabil (the red one, the stabilzer) through a blazer and it made in run better. many say it's just for stabilizing, but in fact it cleans out the fuel lines and the carb/fuel injectors. as always though, don't expect to much a miracle from liquid in a can if it's something mechanical. I had a family member who had a bronco II that had a bad lifter knock and several things else wrong with it. mechanic said he'd be lucky to get another 1,000 miles out of it. The mechainc wanted over 2,000 dollars to fix everything. he said he would instead run it till it blew, and he got another 37,000 miles out of it.

Have you checked the distributor cap on it? i know i had a rough idle in my vehicle until i changed the pcv valve. it was just like 4 dollars and took about 30 seconds to do.
 
Wow Frijid! I never heard of hydrolocking caused by seafoam, but you are right there are many posts discussing it.

BTW... this car has a distributorless ignition system.

I'm guessing that your rough idle was casued by a vacuum leak due to a worn or deteriorated grommet.
 
I'd do a compression and leakdown test. If they are good I'd drive it till/if it dies. Carbon buildup can cause misfires, but if compression/leakdown are good I doubt you have a serious problem.

Carbon flakes off and prevents valves from sealing properly which causes misfires. The carbon works its way out and misfire goes away, but it happened long enough to throw a code.

If they are bad... you're looking at valves/head or rings/block.

Or get an engine from a salvage yard...
 
With all due respect, I've seen this problem before. You need to go to a Ford dealer or a reputable repair shop for a diagnosis. The Auto Zone people try to be helpful but in the end only fill your car up with parts that are not needed. It actually costs more to fix the problem in the end. Your problem is probably not a mystery to a seasoned mechanic. Most dealerships charge a $95 diagnostic fee.
If you want to find a good independent repair shop, get a referral from a parts store that garages deal with. They will point you in the right direction of a good repair shop.
 
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Frijid, don't scare people into thinking Seafoam is dangerous, it's not
just use it in the gas.

I buy it by the gallon at my local farm center lol,,,}
have a 24 year old lawn mower,,
nearly 35 year old snowblower,,,
a '93 Grand Cherokee w/ 188K on her
some other stuff that could be record setting on miles {hint Honda's}

I use Seafoam as a preventive maintenance 2~3 times a year along w/ using good gas without ethanol.

Lucas Oil Injector Clear, again get the gallon, will save you more on fuel than the cost of the product,, and your motors run much better
{use a double dose for actual results}
that is run always when not doing a Seafoam treatment:thumbsup:
 
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Frijid, don't scare people into thinking Seafoam is dangerous, it's not
just use it in the gas.

Not throwing off on stabil, i always use just a little bit in the gas tank of my weedeater and lawm mower every spring. I'll fill up the tank run it down to about half, just to "warm it up" then i'll add some stabil in the tank, shake, fill up full with more gas, then shake again. and run the tank down real low to use it all, almost up. I used to do this, then refill after about half tank again, then i realized i'm just "watering" it down with more gas, so i use it almost all up before i add more gas. Of course i run stabil year round anyways, so the two work good together. after i run that "treatment", i don't use seafoam anymore unless i would have trouble, (which, gladly i haven't had any trouble). the only thing i continute to use is stabil all the time. I also put some in my truck. I'm not afraid of it, i just wouldn't put any into the oil or intake lines. FWIW, stabil now makes an ethanol treatment. I have used seafoam spray in a chainsaw carb and it worked good. Another good product, made by the same company that makes stabil, is called start your engines. I've never had to use it personally, but i recommneded to a neighbor on his lawn mower he never took care of and it fixed it. anything from Stabil, seafoam, seafoam spray, and start your engines, is about the only stuff like that i'd use. I've heard a product called star tron is good to.

But anyways, my main point for coming here was to ask the OP, what ever became of your problem, did you get it lined out?
 
Hi, guys. Sorry for not posting back here sooner.

My car is currently 2,050 miles away at work and I am now home with family.
The "problem" is on stasis until I am reunited with my vehicle.

Before I left though, a few things became clear:

1) The AutoZone people mean well, but are guessing. I don't think they are deliberately trying to bilk me, but I also don't think they really know what they are doing.

2) We have a mechanic back where I grew up, and while he is pricey, I am pretty sure he could figure this out.

3) I am not prepared to sink a lot of money into this car.

4) When I am again driving the car I will try the SeaFoam trick in the gas tank.

5) Most of the tests members have suggested are beyond, if not my ability, my comfort level.

6) The last thing AutoZone said was, "We put in that fuel line cleaner. Now, drive your car normally until your next oil change,
and then we'll take another look at it, for free. It is possible the problem will go away by then."

This is not awe inspiring.

7) When I am again driving the car regularly, I could demand a refund from AutoZone, stating that despite the "diagnostic" and swapped coil pack,
the misfire is still there.

8) The last time I was there, the mechanic said that while it was still misfiring, the "misfire count" was much less, indicating that
the problem was ebbing away. I do not know whether, or even if, this is possible.

I'll post back here when I am driving the car again regularly.
 
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