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Y'all's forum has been helpful. Here's my contribution:

As an avid reader, but ne'er poster or contributor, here is a summary of my 1999 Ford Taurus DOHC (160-170k miles), problems, and their eventual solution.

Feel free to comment or correct my errors, I'm just a hack. But my problems seem to be common across this model year, so here's how I fixed it, after extensively reading other posts in this forum. Hopefully some commentators will add more links and feedback.

Note that all these issues were fixed with "standard" tools, nothing fancy or special. A 8MM and 10MM ratchet, spark plug socket, needle nose pliers, and a flathead screwdriver is almost enough to do all the work below.

The parts you can get online. Spend a few minutes to compare online prices with the standard parts box shops.

Multiple System Failure Syndrome Overview-> I had multiple strange symptoms that ended up being multiple problems that I fixed over the course of about 1 year. Most of it had to do with a completely clogged EGR system, disintegrating vacuum lines, possible faulty ignition system, and a bad EGR/IAC valve.

SYMPTOMS:

#1. The car RPM would surge suddenly, especially when cold, without regard for being in park or drive. This was dangerous, especially in reverse.

#2. When at operating temperature, the car would hesitate or misfire on acceleration, or shudder and hesitate to shift gears. This almost felt like a transmission issue.

#3. After #1 was fixed, I partially fixed #2, but the car would stumble and miss at idle, especially if the air conditioner was on, and the issues in #2 would come back, but not quite as bad as before.

#4. Several codes were appearing in conjunction with a check engine light, including Cylinder #4 misfires and EGR issues, but were generally not present for problem #3.

GENERAL SOLUTIONS

Problem #1 -> This appeared to be a two fold issue: I replaced the Idle Air Control Valve and fixed a massive vaccuum leak (hole) where the EGR line and the fuel vaccuum control line attach. Either of these problems could have been the cause. I did not attempt to clean the old IAC valve, but I did notice that merely replacing the IAC valve was not enough to fix the overall problem.

Problem #2 -> This issue I diminished by about 60% by replacing the EGR valve and some tubing and cleaning the EGR ports. Note that the 1999 and similar model years have VERY SMALL ports on the intake manifold that guide the exhaust air from the exhaust into the upper intake manifold. The holes are located behind the throttle body on the intake manifold where the manifold attaches to the body.

You have to take off the throttle body to clean them. My ports were so clogged that I did not even recognize that there were cut ports along the face of the intake manifold where the throttle body bolts on, despite the forum having told me that they exist. I also replaced a the PCV tube which connects in a dark hidden place underneath the intake manifold. Mine was completely rotted out.

I also replaced my intake manifold seals and cleaned the mounting points on the upper and lower intake manifolds with carb cleaner. I also noticed that you can get a deceptive "fix" when the car's CPU/controller gets reset for a time when you pull the battery power. You need to drive a bit before you get a good measure of performance.

Problem #3 -> After I fixed #1 & #2 above, I was still having some hesitation, idiling, and misfire issues as described above, especially at idle the car would shudder badly and also miss shift points or hesitate with the AC on.

I was getting really concerned and got a block tester to check for some blown head gaskets, but the tests came out negative - nothing blown (gratefully). Thus, I decided to keep the car and fix whatever may be wrong up to some reasonable limit.

I then completely rebuilt the majority of the vacuum lines. Specifically the two hoses that come off the throttle body to each of the banks. (Autozone has the funny rubber connectors, but they're not cheap). The rubber parts were completely cracked and even gooey.

I also re-fixed my EGR and fuel vacuum lines which had been sub-par ghetto rigged with a more permanent solution. These two changes helped, but not completely.

Finally I broke down and tore off my intake manifold again. Cleaned everything again and rebuilt almost every cracked vacuum hose I could find. I replaced my PCV valve (when I finally figured out where it was) which should have been done earlier. The valve was completely caked over. When I had the intake manifold off, I decided to just rebuild the electrical system while I was at it, and replaced all 6 plugs, the wires, and the ignition coil.

I also took some 91% isopropyl alcohol and extensively sprayed the air mass sensor and air temperature sensors and let them dry for 2+ hours. (This may not be the safest way to clean those sensors, research this more than I did and do at your own risk).

I also sprayed some WD-40 into the IAC valve (yes, the new one, I would not recommend doing this, I wish I had not because I'm not sure of the long term consequences).

I carefully put everything back together and BAM. It all worked, all problems solved. I am still losing some coolant somewhere, but that's for another day. The engine runs like it was brand new. It's been running perfect for about 3 days and 100 miles or so, and is clearly a new beast. If any failures happen, I'll post more.

INVENTORY ___PARTS USED___

6x Spark Plugs - $40 total
Ignition Coil - $70
Spark plug Wires - $25
IAC Valve & gasket - $50
EGR Valve & gasket - $50
Misc. Vaccuum lines, adapters, screw-down rings, and tubing - $70 Throttle Body Gasket - $10
Intake Manifold Seals - $30
2 cans of Carb Cleaner - $10
Air Filter - $10
PCV Valve - $5

Approx Parts Total: $370.00

DOING THIS OVER AGAIN:

If I was faced with any of these problems from the start, with such an older model car like mine, I would FIRST borrow for FREE (yes, how cool is free) the block tester kit from AutoZone and test for a busted head gasket (this is an easy thing to test).

Assuming that the test came back negative, I would buy all the following parts above, borrow the AutoZone Torque wrench, and do EVERYTHING in one fell swoop.

General Process ->

Take off the upper intake manifold and everything attached to it, including the throttle body, vacuum lines, EGR and IAC valve, etc. Rebuild the entire EGR and other vacuum line system with new tubes and fittings. Throw away the old EGR/IAC valves and put on new ones and new gaskets.

Clean the throttle-body/EGR ports that are on the intake manifold. Clean other holes on the upper intake manifold and the mounting on the lower intake manifold. Completely replace the plugs, wires, and ignition coil (Be careful to mark wires and cylinder numbers). Replace the intake manifold seals and throttle body gasket along with the air filter.

Thus, in one day's work, you can get done almost anything a garage mechanic can do to the upper engine. Also, don't forget that the cam position sensor and the crankshaft sensors also might be good replacement targets if all this fails. While this may seem excessive, this suggested process is relatively cheap both parts and time wise and addresses several other problems that will almost certainly emerge in the future if you keep your Taurus.

Be sure to read all the other posts on these issues, because a lot of this is a summary of other people's posts.

Best of Luck!

Compton Ford
 

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Just for reference

Y'all's forum has been helpful. Here's my contribution:

As an avid reader, but ne'er poster or contributor, here is a summary of my 1999 Ford Taurus DOHC (160-170k miles), problems, and their eventual solution.

Feel free to comment or correct my errors, I'm just a hack. But my problems seem to be common across this model year, so here's how I fixed it, after extensively reading other posts in this forum. Hopefully some commentators will add more links and feedback.

Note that all these issues were fixed with "standard" tools, nothing fancy or special. A 8MM and 10MM ratchet, spark plug socket, needle nose pliers, and a flathead screwdriver is almost enough to do all the work below.

The parts you can get online. Spend a few minutes to compare online prices with the standard parts box shops.

Multiple System Failure Syndrome Overview-> I had multiple strange symptoms that ended up being multiple problems that I fixed over the course of about 1 year. Most of it had to do with a completely clogged EGR system, disintegrating vacuum lines, possible faulty ignition system, and a bad EGR/IAC valve.

SYMPTOMS:

#1. The car RPM would surge suddenly, especially when cold, without regard for being in park or drive. This was dangerous, especially in reverse.

#2. When at operating temperature, the car would hesitate or misfire on acceleration, or shudder and hesitate to shift gears. This almost felt like a transmission issue.

#3. After #1 was fixed, I partially fixed #2, but the car would stumble and miss at idle, especially if the air conditioner was on, and the issues in #2 would come back, but not quite as bad as before.

#4. Several codes were appearing in conjunction with a check engine light, including Cylinder #4 misfires and EGR issues, but were generally not present for problem #3.

GENERAL SOLUTIONS

Problem #1 -> This appeared to be a two fold issue: I replaced the Idle Air Control Valve and fixed a massive vaccuum leak (hole) where the EGR line and the fuel vaccuum control line attach. Either of these problems could have been the cause. I did not attempt to clean the old IAC valve, but I did notice that merely replacing the IAC valve was not enough to fix the overall problem.

Problem #2 -> This issue I diminished by about 60% by replacing the EGR valve and some tubing and cleaning the EGR ports. Note that the 1999 and similar model years have VERY SMALL ports on the intake manifold that guide the exhaust air from the exhaust into the upper intake manifold. The holes are located behind the throttle body on the intake manifold where the manifold attaches to the body.

You have to take off the throttle body to clean them. My ports were so clogged that I did not even recognize that there were cut ports along the face of the intake manifold where the throttle body bolts on, despite the forum having told me that they exist. I also replaced a the PCV tube which connects in a dark hidden place underneath the intake manifold. Mine was completely rotted out.

I also replaced my intake manifold seals and cleaned the mounting points on the upper and lower intake manifolds with carb cleaner. I also noticed that you can get a deceptive "fix" when the car's CPU/controller gets reset for a time when you pull the battery power. You need to drive a bit before you get a good measure of performance.

Problem #3 -> After I fixed #1 & #2 above, I was still having some hesitation, idiling, and misfire issues as described above, especially at idle the car would shudder badly and also miss shift points or hesitate with the AC on.

I was getting really concerned and got a block tester to check for some blown head gaskets, but the tests came out negative - nothing blown (gratefully). Thus, I decided to keep the car and fix whatever may be wrong up to some reasonable limit.

I then completely rebuilt the majority of the vacuum lines. Specifically the two hoses that come off the throttle body to each of the banks. (Autozone has the funny rubber connectors, but they're not cheap). The rubber parts were completely cracked and even gooey.

I also re-fixed my EGR and fuel vacuum lines which had been sub-par ghetto rigged with a more permanent solution. These two changes helped, but not completely.

Finally I broke down and tore off my intake manifold again. Cleaned everything again and rebuilt almost every cracked vacuum hose I could find. I replaced my PCV valve (when I finally figured out where it was) which should have been done earlier. The valve was completely caked over. When I had the intake manifold off, I decided to just rebuild the electrical system while I was at it, and replaced all 6 plugs, the wires, and the ignition coil.

I also took some 91% isopropyl alcohol and extensively sprayed the air mass sensor and air temperature sensors and let them dry for 2+ hours. (This may not be the safest way to clean those sensors, research this more than I did and do at your own risk).

I also sprayed some WD-40 into the IAC valve (yes, the new one, I would not recommend doing this, I wish I had not because I'm not sure of the long term consequences).

I carefully put everything back together and BAM. It all worked, all problems solved. I am still losing some coolant somewhere, but that's for another day. The engine runs like it was brand new. It's been running perfect for about 3 days and 100 miles or so, and is clearly a new beast. If any failures happen, I'll post more.

INVENTORY ___PARTS USED___

6x Spark Plugs - $40 total
Ignition Coil - $70
Spark plug Wires - $25
IAC Valve & gasket - $50
EGR Valve & gasket - $50
Misc. Vaccuum lines, adapters, screw-down rings, and tubing - $70 Throttle Body Gasket - $10
Intake Manifold Seals - $30
2 cans of Carb Cleaner - $10
Air Filter - $10
PCV Valve - $5

Approx Parts Total: $370.00

DOING THIS OVER AGAIN:

If I was faced with any of these problems from the start, with such an older model car like mine, I would FIRST borrow for FREE (yes, how cool is free) the block tester kit from AutoZone and test for a busted head gasket (this is an easy thing to test).

Assuming that the test came back negative, I would buy all the following parts above, borrow the AutoZone Torque wrench, and do EVERYTHING in one fell swoop.

General Process ->

Take off the upper intake manifold and everything attached to it, including the throttle body, vacuum lines, EGR and IAC valve, etc. Rebuild the entire EGR and other vacuum line system with new tubes and fittings. Throw away the old EGR/IAC valves and put on new ones and new gaskets.

Clean the throttle-body/EGR ports that are on the intake manifold. Clean other holes on the upper intake manifold and the mounting on the lower intake manifold. Completely replace the plugs, wires, and ignition coil (Be careful to mark wires and cylinder numbers). Replace the intake manifold seals and throttle body gasket along with the air filter.

Thus, in one day's work, you can get done almost anything a garage mechanic can do to the upper engine. Also, don't forget that the cam position sensor and the crankshaft sensors also might be good replacement targets if all this fails. While this may seem excessive, this suggested process is relatively cheap both parts and time wise and addresses several other problems that will almost certainly emerge in the future if you keep your Taurus.

Be sure to read all the other posts on these issues, because a lot of this is a summary of other people's posts.

Best of Luck!

Compton Ford

Might add a low cost fix for the clean air supply to the valve covers .

See pic. This should last better than the market elbow. I have 2 cars that needed them, and thus my fix. Just sharing.

My original thought, based on old school cars was this was just clean air supply to the crankcase and if they are broken, you just get dirty air in the crankcase, some bugs and such. NOT SO.

This air is measured air by the MAF and with that off you have two issues. Unmeasured air going into the crankcase and to the PCV. Also that leaves opening in the accordian for dirty air to get in and unmeasured air to get in. All in all, bad running and dirty stuff.

Good feedback on your fixes.

-chart-
 
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