I've been fighting for the last two months, trying to figure out what has been setting these codes off on my 2000 Windstar, 49,000 miles (P0171, P0174, system too lean, bank one, bank two). I checked out almost every website imaginable that discussed what could be setting the warning light off. I finally realized that the codes started coming up right after I put a bunch of that injector cleaner in my car's fuel a couple of months ago when it was riding rough. Well, I bit the bullet one afternoon about three weeks ago (after I had done almost everything else to remedy the problem) and changed all three of the oxygen sensors (yep, three: one before, and two after the cat. converter), and now it's running perfectly with NO codes popping up, and I've got alot better pick-up with better gas milage! From what I've learned, people don't notice that they have two in the rear section and only change one, which doesn't clear the problem up totally. As far as why the situation occurred in the first place; it was that stupid injector cleaner I added to the fuel that caused the O2 sensors to get fouled up. (It was kinda strange that the codes would pop up when the weather would change rapidly from cold to warm during the day). As far as the engine running rough, all I needed was to spray some cleaner in the manifold and the rough idling straightened out. These sensor things really drive me nuts! I liked it when I had my 85 Chevy where I could actually fix it in the driveway and have feel confident that I knew how to fix whatever problem had come up. I hope all of you out there with these 171/174 demon codes are as lucky as I was!

It's the opposite for me. I never want to see another carburator in my life. Give me an intelligent fuel/ignition system anyday over a bunch of linkages, rods, plungers, jets, oriffices, diaphrams and other mechanical gobbledygook. I can actually program the computer to run leaner here, and richer there over all temp ranges and altitudes. It's all so easy once you get your mind around it. PS, I've been tinkering for almost 40 years now. Used to be able to rebuild carbs (SU were a specialty) with my eyes closed. I could tune a multi carb setup with basic, BASIC tools. Fuel Injection was a BIG change, and confusing for a while. But I'll never go back. Even a mid 60's Ferrari 265 GTB or a 64 GTO with the trip dueces' would be hard put to tempt me.

Just curious: What brand of cleaner did you use? I'm about to pour two bottles of Chevron Techron into our 1996 Windstar. I rarely use these cleaners, but I've never had a problem when I've used the Techron. Thanks! Mark Salvetti Saugus, MA

First, READ THE INSTRUCTIONS.... It should state on the label in fairly big letters "SAFE FOR O2 SENSORS" Two bottles seems to be an awful lot. Seems to me I remember 1 bottle being recommended for up to 21 gallons. And NEVER use these kinds of cleaners more then once bewteen oil changes. They wash down the cylinder walls and dilute the oil.

Thanks for the info. I have been experiencing intermittent O2 codes on my 96 for a while. I did replace two of the sensors, one on the from bank and one at the convertor. I think there are two more on the car. I know one looks like a bear to get to and I need to see if there is a fourth. I think mine has 4 sensors. Keith

Thanks Steve. Techron is safe for catalytic converters and O2 sensors. Regarding the gallons treated, the large 20 ounce bottle treated 21 gallons. But I haven't seen that size for a while. I think it's because it would be the most expensive treatment on the shelf. Instead they seem to market the smaller bottles that treat up to 12 gallons each, and are priced more in line with their competitors. But if you read the label, you need to buy two. In the past I've only used Techron just before a scheduled oil change to avoid the dilution problem. Thanks! Mark

The name of the cleaner escapes me, but I bought it at Advanced Auto Parts, and it was one of those high-Tech specialty cleaners. Dumb- butt me should have really read the back of the bottle because it probably had some sort of warning about putting in in a newer engine. With my old '85, I could throw just about anything in the gas tank and it wouldn't hurt the system. These new things, you have to be very careful. The guy at the dealership repair shop once told me that if you put super unleaded in the van all of the time, that it could effect performance in a negative way (probably because of the additives), so I always use a medium grade gasoline. A guy at Auto Zone told me that his engine light on his Windstar came on and displayed the same codes when he would drive in high mountain areas of Colorado. Maybe it's like that temperature change/ humidity thing I noticed here in New Orleans. maybe when the sensors are dirty, that sort of thing makes them go off..... my guessing again....

Hell, I'm beginning to believe it's caused by sunspots!!  How could so many have these codes come in at the same time unless it was weather related.  I got these codes last week on my 2000 and had the codes read at Auto Zone also.  As my previous experience told me, there was some issue in the fuel mixture but for me it was cleared up by using some HEET (dry gas).  The rapid weather changes causes an unusually high amount of moisture in the gas tank that is not kept filled and mine had been low for a couple days.  I poured the HEET in, cleared the codes and have driven about three tankfuls since with no lights!   Steven L. Bettendorf,