Questions and Answers

Windstar Exhaust Modifications Q. Hello, I hope that you can help me with some information. I own a 1999 Ford Windstar with the 3.8 liter V-6 engine. I am planning to change/replace the exhaust system to make the vehicle run cooler, smoother, and have more power. My question involves the catalytic converters.

I am planning on removing or "gutting" the two catalytic converters and am wondering what effect this removal will have on the way the O2 sensors operate.

There are four sensors, two on each side of the V-6. One sensor on each bank is placed between the engine and the catalytic converters as a reference for the computer to adjust mixture, I believe. The third is placed behind the converter on one side and the fourth is placed directly in the converter on the opposite bank of cylinders.

My question is will removing the catalytic converter element or completely removing the catalytic converters alter the O2 readings to cause a "check engine light" to appear? I heard this check engine light will light because the computer will sense a failure of the catalytic converters because the readings in each bank will be the same.

I realize that the sensors in both banks will read the same because of the fact that the catalytic converters will be gone and, in essence, it would be like the same reading at two points in the exhaust system without any catalytic converter action taking place. If this will cause a problem with the computer, can one catalytic converter be removed and both O2 sensors in that bank be "unplugged", leaving just one catalytic converter and two O2 sensors for the computer to work with?

Can all four O2 sensors be removed without screwing up the mixture readings? Aren't four O2 sensors a bit much? Don't they just duplicate each other's readings? I am also planning to remove the "pillow" shaped resonator and replace the 1 7/8" pipe from the rear of the "flex tube" that allows exhaust pipe movement with the engine, to the muffler with a 2 1/2" straight pipe and add a performance super quiet flow through muffler (Flowmaster Delta Flow 70 series Truck Muffler). I am hoping to have quiet performance and more fuel economy.

I HAVE DONE THIS PROCEDURE BEFORE TO OTHER VEHICLES WITH EXCELLENT RESULTS.

I have a 1993 Ford Thunderbird LX 5.0 (302 V-8) that I bought new which now has over 171,000 trouble free miles. I removed the two resonators, both catalytic converters, and replaced the two mufflers with quiet performance models years ago and have had NO problems with the O2 sensors on this model.

The engine doesn't burn a drop of oil between changes, runs cooler than it did as factory stock, and gets excellent fuel economy, a 15.2% increase from stock 23 mpg to 26.5 mpg average even after 170,000 miles. It only has two O2 sensors, and both were located upstream from the catalytic converters so I didn't need to worry about any "after" (downstream) catalytic converter readings affecting my computer and causing driveability problems.

Can you help me with my project? I do realize that in some circles, this project is considered illegal, however, could you just explain how you believe this project would affect the computer mixture readings on this model,(Windstar), if at all? I'm really not sure about the four O2 sensors and the sensor directly mounted in one of the converters and how to remove them without problems.

Thank you,
Jim

A. First of all, it is against Federal law to do what you did to your Ford Thunderbird and plan to do on your Ford Windstar. There is a very heavy fine and possible imprisonment for violating this law. Furthermore it is illegal to sell a vehicle with tampered emission systems. So if you trade it in, at a dealer, on a new car, they will probably report the violation to the EPA.

If you sell it to a private individual, they would be obligated, under the law, to report it. I guess it's safe to assume the state you live in does not have emission testing, I say that because there would be no way either vehicle would pass inspection.

Now, with that said, you can do whatever you want with the car. But by law I can't help you tamper or modify the emission systems in any way.

The reason your Ford Windstar has four HO2S is that the monitor both catalytic converters. If one goes bad the computer will be able to tell which one went bad, throw a DTC and alert the driver. If one, or both, catalytic converters are removed, the results would be the same. The computer will see the missing catalytic converters, throw a DTC and alert the driver. A HO2S can not be left unplugged because the computer will see an open circuit, throw a DTC and alert the driver. The HO2S can not be bypassed. The computer will see it as a short, throw a DTC and alert the driver.

If the computer detects any missing inputs, it will use a set of values stored in memory. These values are not optimal so milage will decrease. So if you disconnect all four HO2S's and somehow keep the MIL from coming on, the computer will go to it's stored values and compute fuel mixture from that.