1997 TaurusWagon 3.0L (VIN "U") Runs Rough, Loses Power



My Taurus wagon (bought recently for $900.00) runs and drives fine for about 30-40 minutes after a cold start. But after that, I start to notice a loss of power when going up hills. My speed will decrease from, say, 65 to 55 or slower on moderate grades desite keeping the foot feed steady.

This problem appears sooner when I get into heavy stop-and-go traffic. The loss of power gets so bad I have to pull over and shut the engine down and let things cool off for ten minutes or so and then I can drive normally for about ten minutes before I get the loss of power again.

Every once in a while I get a whiff of something that smells like, well, like it is very hot. I can’t explain it any better than that. I wondered if the catalytic converter was getting excessively hot, so I looked under the car to see if it was red. It was not.

Let’ see - other relevant facts about the car – the previous owner let the car sit without being run for a year. It was run maybe three times during that time. There was 1/3 of a tank of gas in the car from the time it sat idle, and I put in a can of Sea Foam together with 2/3 of a tank of fresh gas.

Also, I am getting a “Service Engine Soon” light with codes P0305, P0306 (cylinder 5 and 6 misfires), as well as P0430, Catalyst efficiency on Bank 2.

Any diagnostic insights would be appreciated!




First you need to deal with the check engine light. A misfire if severe enough will cause converter damage. Since your Taurus is DIS there is no distributor. Cylinders 5 and 6 run off of seperate coils so I doubt that is the problem. Most likely it is in desperate need of plugs and wires. I would also recommend a fuel filter and air filter. Once this is taken care of the loss of power can be addressed if it still exists. It is possible that 1 of the 3 converters is failing as well. Take care of the misfire first and let us know.


OK will do the tuneup and report back.


If plugs and wires don’t fix it then I would consider the possibility of a mechanical problem since 5 and 6 are adjacent to each other.

Two cylinders down will definitely kill the power. If plugs/wires does not fix it then if it were me I would connect a vacuum gauge and/or run a compression check.
Two misfiring cylinders adjacent to each other can sometimes mean a head gasket problem. Hopefully that is not the case considering the 3.0 is a pretty rock solid engine.


Is the power loss greater at higher speeds? I suspect the converter. You may have more than one problem.


I am not experienced with the use of Sea Foam on newer cars. So I may be wrong, but I thought it is for use on boats and small engines that don’t have Catalytic converters and other modern controlls. You may want to make sure it is OK to use with modern emission controls. It may be causing some of the issues.

With respect to OK445’s comment about the head gasket failing. Some things to confirm this possibility are:

View the color of exhaust. If is has a white smokey color it suggest antifreeze is leaking in to a cylinder.

Check the oil and make sure there are no droplets of water on the dip stick.

Has the engine overheated or is it running hot. Overheating can cause the head gasket to fail. If yes, was the cause clearly identified and corrected?
Monitor the level of the anti freeze/coolant. If there are no obvious leaks and the level drops it is likely being burned in the engine. Do you see large swings in the temp gage while driving? If so, this is a sign that the level of coolant is too low.

Good luck.


One thing about the headgaskets, the previous owner supplied me with a receipt documenting the fact that she got the head gaskets replaced, heads resurfaced, etc, and compression checked (after heads/gasklets were replaced) in July 2006, just before she let the car sit for the year. The job ran her some $1600.00. So hopefully the job got done right and it is not a head gasket problem this time…

My sons are doing the plugs and wires today so we’ll see if that helps…


Both high speeds and lower speeds depending on the traffic conditions. If it is highways speeds, I do not notice a problem until I have been driving for 30-40 minutes, and then the probklem is only at high speeds. If stop and go traffic, the problems appear much sooner, and the car will lose power and stall. Then, as I said, I need to shut down for several minutes and let things cool off and then it is fine again for a while.


No, engine does not run hot at all.


Here is the latest… My sons replaced the plugs and wires last night, didn’t replace the air cleaner because it was clean and did not need replacing.

The engine idles and runs a lot smoother now.

I have not had the chance to test the car in stop and go traffic yet (but will this afternoon), but I did take it out on he highway for about 40 minutes last night. The first fifteen minutes, it performed fine. I could accelerate up hills, maintaining 65 mph, and overall car felt fine.

I drove into a nearby town, turned around, and headed back home. Once on the highway, I again tested accelerating from 60 mph and soon when I did that it was like I had a “governor on the carburetor” [I know this car does not have a carburetor, but that is what it felt like]. The thing would not go faster than 60, but otherwise the engine ran fine.

I also tried putting the cruise control on 60 mph, and it did fine on level road and downgrades, but on upgrades and hills, the tach and speedo needles entered a free fall. I am sure the car would have stalled altogether if I had not disengaged the cruise control and eased off the gas pedal until things would “even out” and then I could slowly accelerate to 55-60mph.

I tried mashing the accelerator a few more times, but ran into the “governor effect” each time. It was like the engine was starved for air or something and would just hit a wall.

I drove the car to work this morning (65 miles, highway speeds) and the car did fine though I did not drive it hard because I wanted to actually make it to my office. About five miles into the trip the SES light came on again, so I’ll have to get the codes read tonight.

Anyway, that is the latest. Any further thoughts from anyone?




For a diagnostic test, put in a 185F Tstat and a gray plastic bottle of Bars stop leak in the radiator. At this point it cant hurt, my Taurus has been running with the above sed for 40K. To put frankly this car has the cooling system from Hell.


I would start suspecting a clogged converter then. This could be verified with a vacuum gauge.

A converter can become clogged due to a chronic engine miss, which you have had.
There gets to be a point where about half the honeycomb in there is plugged up solid, and the car will exhibit those symptoms you mention.


Here is an update:

My sons did the plugs and wires, and I went ahead and put in a new air filter. I also put in another can of Sea Foam and a fresh tank of Shell regular unleaded.

The car is doing a bit better, meaning I can go a bit further/longer with out problems than I used to. But the car does not like hilly terrain at highway speeds. I lose power, and then have to shut down for a few minutes for things to be right again.

I got the codes read again. Here is what I am now getting.

P1506 - something about IAC circuit. Might this possibly expalain the slightly high, loping idle?
P0420 - catalyst efficiency under threshhold I believe on bank 1
P0430 - catalyst efficiency under threshhold I believe on bank 2
P0302 - misfire detected on cylinder 2.

I guess the next step is to check the air intake for leaks, check throttle body for dirt, as well as the IAC?





My opinion is still the same.
The IAC and lopey idle is the Idle Air Control, BUT, this may be affected by something else.
I would still check for a clogged converter. A clogged cat affects the manifold vacuum and richens the fuel mix, which in turn the computer attempts at least to control. And probably not able to do it either.


Reaaally dumb question: How do you check to see if the converter is clogged? Do I just pull it (them, as I guess there are two converters on my taurus) and see if the engine performs better?


That can be done but it’s a bit noisy. If your neighbors are total boors then that’s how I would do it. :slight_smile:

I use a vacuum gauge; it’s much easier and faster, and I would highly recommend buying one. They’re cheap, simple to use, and can tell you a lot of things about an engine.


OK here is the latest. Finished replacing the exhaust system including the catalytic converter on Saturday. The loss of power problem is gone. I can run the carn in traffic or on the highway and accelerate from 65 to 75 up hills with no problem.

The car idles smooth, but the idle is still fast, I think. The idle is 2000 rpm in park or neutral, and 1000 rpm in gear.