Taurus Car Club of America : Ford Taurus Forum banner

1999 Taurus Dohc Misfire Questions

7K views 22 replies 11 participants last post by  sfontain  
#1 ·
First off, I'm in need of assistance. :lol2:

Details:
- 1999 Taurus, Duratec, 62,000 miles.

- Maintenance: new plugs, new wires, new PVC valve, new fuel filter, air filter, upper intake gasket, BG Products injector cleaner, etc. - all performed over the past 6 months.

- I've been experiencing a weird mis-fire with my vehicle, which has still remained even though I've completed the above-indicated maintenance tasks.

It seems to happen when I'm going 20 - 30 MPH and trying to accelerate to highway speeds. It also happens at 20 - 30 MPH when trying to climb a hill. Also, it happens when I have the car in the driveway when I rev it to 3,500 - 4,000 RPM range.

No codes are getting set - to check engine light, etc.

Am I overlooking anything? Possibly, a coil issue? I've read of some other members having weird mis-fire issues caused by a bad coil.

thanks! :)
 
#6 ·
Age is the main factor that will determine whether or not the gaskets can be re-used. Inspect each one before re-using them to ensure the rubber gasket material did not expand. When these gaskets are "freed", the blue rubber gasket can expand and no longer seats correctly.

When you replaced the wires, did you squirt some dielectric grease or silicone grease into the plug boots? If not, the plug connector inside the plug boot can ground to the engine instead of the plug and result in a misfire.
 
#7 ·
Originally posted by Baby SHO@Feb 16 2005, 11:13 AM
make sure to use motorcraft plugs and wires, aftermarket ones have cause problems on tec's. Bosch are the worst.

Brad
Smart Man I have seen at least 3 sets of these Bad even NEW. Have helped 2 other here with problems with plugs. Here is the famous plug question. Does it backfire at WOT (wide open throttle) in Park? When you let off it should happen. Even if you just Rev it up nicely it may happen. If it does change the plugs. Look at my past posts and there is a thread with this guys problems. They sound similar. Good Luck.
 
#8 ·
i'm having the same problems with my 2001 taurus duratec. all i did was change the plugs. used autolite platinums. gapped .54. all my buddies tell me its a wire or a coil pack problem. i'm going to pull the plugs and squirt same dielectic grease into the boots. will let you know what happens. have you tried any of the other solutions that suggestions? if you get yours fixed, please advised me and i will do the same. thanks
 
#9 ·
I do have updates:

1) The plug wires that I utilized were Napa wires. I did use the dielectric grease on the boots that was included in the package.

2) The plugs that I used were Autolite Double Platinum plugs.

I purchased a vacuum gauge this evening - my old, trusty one that I purchased about 25 years ago is no longer with me. I checked the vacuum by removing the connection at the fuel rail.

Results of vacuum test: 21 inches - and steady.

The misfire issue happens when I keep the throttle at a maintained speed of 20-30 m.p.h. when driving in my community - and also happens when climbing smaller hills. Additionally, it still mis-fires at 4,000 RPM when I have it in park, but as indicated earlier, this could potentially be a failsafe for the engine created by Ford.
 
#10 ·
Yes.. in park or neutral, the rev limiter kicks in and prevents the engine from going over 4000 rpm or so... it'll do a weird rolling stumble kinda thing...

In regards to your vacuum check, you can have a vacuum leak while the gauge still reads 21 inches - the engine will produce enough vacuum to keep the gauge that high, but it'll be sucking unmetered air in thru the leak point, causing problems. I don't suspect this is it tho, because a vacuum leak large enough to cause a problem should have set a lean code by now. One way to check for a vacuum leak is to spray suspect areas with a garden hose - if there's a leak, it will draw in the water and cause the engine to run rough - in worst cases, you can actually hear the water being sucked in - kinda the slurping noise you make when you drink thru a straw and it's almost gone.

At a steady 20-30 mph, the EGR system is likely coming on - it's possible that the EGR ports in your intake manifold are getting plugged, and causing more EGR gas to flow into the cylinders farther from the valve, making them miss. It's pretty common on the 3.8 litre engines used on the newer windstars, and even some of the 4.2's, but not so much on the 'tecs that i know of.. but still a possibility. No real way you can tell tho, without the equipment to do a power balance test, unless you wanna pull your upper intake off and actually look at the EGR ports to see if they're restricted. If they are, you can just clean them out with a drill bit or small wire brush. Otherwise, my advice is take it to a good shop or the dealer and get them to have a look. Even if you just pay them to diagnose it, you may be able to make the repair once you know what's wrong.
 
#11 ·
The engine has a rev limiter to prevent the engine from climbing above 4000rpm when it's in park.

I have the Autolite DP's as well, and think they are fine. I usually like everything with the Napa name, but I'd be wary of the wires for this engine.... it's really very picky....

did you keep the old wires by chance? They are designed to last 100K miles, if you saved them, put them back on and see if you still have misfires.

My misfire never resulted in a OBD code.
 
#12 ·
This evening, I had a bit of time to work through a few more things on my Taurus.

1) Checked the primary and secondary resistance at the coil. Everything seems within spec. No need to spend $75.00 on a replacement coil at this point in time.

2) I headed for AutoZone and picked up the *real* plugs for my vehicle - Motorcraft plugs. It was already after 8:00 P.M. by that point, so I could only install the front 3 plugs.

3) While at AutoZone, I purchased a few more packs of dielectric grease. The new plug wires that I installed 6 months ago were already dry at the boot level where they attach to the plugs. Needless to say, I put a good swirl of the grease on the inside of the front 3 boots before placing them back on the new plugs. I've found that using a Q-tip does a pretty good job of swirling the grease around the inside of the plug boot.

I only road tested it enough this evening to make sure it'll fire up when I hit the road for work at 5:30 in the morning. Over the next few days, I'll get the rear 3 plugs swapped out and some more grease on those plug boots, too.

I've contacted a good local repair shop - recommended by Pat Goss actually, which I'll use in the event the plug repacement doesn't resolve all the issues. Diagnostic fees will run about $98.00. However, that still has to be way less than the stealership will charge.

Finally, something did come to mind a few days back when I was trying to sort through these issues with my car. I used to own a 1989 Chevy Corsica with a V-6 - may God rest my soul. About 10 years back, the blasted car was really behaving wierd in how it ran. I even went as far as replacing the idle air control valve, to no avail. I spent $39.99 in "diagnostic fees" to Pep Boys - may God rest my soul for the 2nd time. Pep Boys actually "fixed" my Corsica for $39.99. Apparently, they had a skilled mechanic in the shop and during the process of running the diagnostics, he reset the ECM on the car. He then left the car to idle for about 20 minutes while the computer set up the right drivability scenarios. In the process of all my maintenance on the car, I had been resetting the ECM, but driving it to "teach" the computer as instructed in the repair manuals. Go figure.

Oh, some searching on the 'Net revealed that there's some Ford Contour owners who have also had some mis-fire issues with their 3.0L Contours. This thread that I'm linking is a bit long. However, a good read. Some of the posters went as far as replacing their coils, but the situation didn't improve. Others replaced their coils and had good results. One person tested his coil and it had more resistance after the car was warmed up, but would read normal resistance levels when the car was cool. A new coil worked for him.
Contour 3.0L Misfire Issues

:chili: :chili:
 
#15 ·
I thought I would add a quick update to my post. So far:

1) I've only replaced the front 3 plugs with Motorcraft plugs. Still misfires a bit under a medium load.
2) I ordered, and received the Motorcraft plug wires.
3) I installed a new, Borg-Warner coil pack. The misfire appears to be solved.

I was going to work on installing the 3 remaining plugs in the back this weekend with the new plug wires. However, my tranny dumped on me. :(
$1,800 - $2,100 to get it rebuilt.
 
#17 ·
Originally posted by sfontain@Mar 25 2005, 08:27 PM
You need to replace all 6 plugs at the same time or it may not run right.
I hear ya'. Actually, it has been running quite good with 3 Autolite and 3 Motorcraft plugs - along with the new coil. As soon as I get my Tuarus back from the tranny shop, I'll finish the ignition work.
 
#19 ·
I have what I believe to be a *final* update for this post. The tranny rebuild had my car off the road for a little over a week and I couldn't work the misfire issues.

The coil pack that I replaced didn't appear to resolve the issue as I had originally thought. However, the old coil pack was a bit rusty and scaly on the underside. While I hate to replace parts that are not really worn out, I figure that I'll still be a bit ahead of the game as who really knows how long the original coil would last.

Final parts purchase:
1) Motorcraft plug wires.
2) "professional" size container of dielectric grease.
3) D.P.F.E. sensor.

This evening, I located that blasted sensor. Got it out and installed the new one. Heck, doing the replacement of the DPFE sensor takes about as long as replacing all 6 plugs on this engine.

I then went through the process of replacing the plug wires. I used a Q-Tip to circulate a layer of dielectric grease in both ends of the boots. The clips which connect the boots to the coil fit *nice and tight* and this is an area where the Napa wires were quite weak. The Napa wires had some horrible clips which barely held the boots on the coil.

The original DPFE sensor was made out of pot metal. I wonder if this material allowed the device to conduct more heat and lead to an earlier failure? The replacement one was made out of plastic. Hopefully, it will hold out on me long enough.

For anyone replacing the D.P.F.E. sensor on the '99 Duratec engine, the sensor is located about 3" away from the tranny dipstick. You have to pull off the rubber accordian link for your air intake and with a good worklight, you should be able to see the sensor, the two tubes connected to it, the electrical connector and the two nuts holding it on. The area is quite tight to work in, but I have larger hands and was able to complete the task.

Well, with all the work done, I did the road test. In one word, SMOOTH comes to mind. I feel good that this issue seems to be behind me. Between the plugs, wires, coil and DPFE sensor, I paid a little over $150 - but, well worth it when compared to what it may have run to have a shop do it.
 
#20 ·
IMHO people tend to be remarkably un-suspicious of their wires when misfire occurs. Sometimes people post on forums and say, "My Taurus has 120K miles and it's misfiring," and when I ask if they've changed their wires, they usually say, "No, but I replaced my spark plugs." 60K isn't too early for wires to fail, particularly on a 6-year-old car.

But, hey, maybe it was just your DPFE sensor. :)
 
#21 ·
I have another quick update to provide. The past few months, I've been real busy with working (I work two jobs, mon).

This past Saturday, I was all set to replace the rear 3 Autolite plugs with the Motorcraft plugs. However, I thought I'd first pull out the front 3 Motorcraft plugs and check their condition, gap and reinstall them using some anti-seize compound on the threads. Two of the 3 plugs, were playing rough with me and wouldn't allow the threads to get started so I could get them into cylinder. Being 2 plugs down, I was stuck. One car, two bicycles with flat tires and a mile away from Advance Auto. So, I hoofed it to the store.

The selection was abysmal for plugs. More Autolite double platinum, Champion copper, some NGKs that were $10 each and required special order and the Bosch plugs. I was going to try the Autolite plugs (again) but they only had 2 in stock. I guess someone was trying to send me a message. :)

I opted for the Bosch single platinum plugs (#4205) and headed home. The plugs were well-packed and had cardboard cylinders around the threads to prevent the pre-set gap from getting changed during shipment. These bad boys were about $2.00 each.

I went ahead and installed them. On Saturday evening and Sunday, I had some opportunities for road trips. I put a fair amount of miles on my car over those two days. I've gotta say, my car has never run better.

I'm not sure why Bosch gets the bad wrap. They really seem like great plugs and I wouldn't hesitate to use them again when the time comes for replacing them. My 99 Taurus with 69K drives like new.
 
#22 ·
There is a reason why people say they are crap. See the sticky post. Bosch plugs have a statistical failure rate of over 34% in the SHORT-TERM (well before replacement interval). Most, if not all, of those problems are with the +2 and +4 plugs. The singles aren't terrible, but are not as good as Motorcrafts.

I have had problems with dielectric grease on the plugs and I don't recommend using it. After a few thousand miles @ 1000 degrees or so, the stuff crystallizes and can cause misfiring if any of it strays onto the conductor of the plug or wire. I know this from experience. I've never had a problem with stuck boots that couldn't be solved by lightly gripping the boot w/ channel locks over the insulator of the plug and twisting.
 
#23 ·
The Bosch plugs are junk. They are not built to anywhere near the same dimensions as the Motorcrafts, while the Autolites are virtually identical. The Bosch plugs also die early on a LOT of vehicles, if they don't cause misfiring right from the start.

Btw (just a suggestion) I wouldn't bother with the anti-seize. If you drive your car at all you will be removing the plugs again before they get hard to remove without anti-seize. I just changed the plugs in my 3-year-old Taurus that had 35K on it at the time and all 6 plugs came out very easily.