'98 3.8L Check Engine Light P0174

My '98 Windstar (3.8L Engine) has a code P0174. The guy at Autozone says it needs a new oxygen sensor. Before I continue, I want to make sure I'm doing the right thing.

The van runs fine, but has been been a little hard to start since the CEL came on.

The van recently had the head gaskets changed and upper/lower intake manifold gaskets changed. This was due to coolant getting into the cylindars (white smokey exhaust). Wiswind said on an earlier thread that coolant can ruin the oxygen sensors.

Since the P0171 code was NOT present, should I go ahead and change out the oxygen sensor? I've not done any other preventative maintenance (cleaning the MAF, changing the PCV valve, etc.).

Thanks a ton!

Don't change the O2 sensor just yet.

P174 Indicates a lean condition on one of the two banks (P171 is the sister code for the other bank).

It could be an O2 sensor but it could actually be a lean condition due to an intake leak or a faulty Fuel injector.

It could also be that the 171 code is waiting to appear or you have low fuel pressure.

Investigate a litlle more. I think O2 sensors are blamed far too often usually they are only the messengers.

I had P0171/P0174 on my 93 Escort 1.9L. It was a dirty MAF sensor - just downstream from the air cleaner. Mine needed a "tamper proof Torx". The wire filament looked hairy. Cleaned it with electrical component cleaner. I'd do the free stuff first.

If you do end up messing with the oxygen sensors....I would switch the 2 "upstream" sensors.....the "upstream" sensors are the ones that are before the catalytic converters.....use a little high temp anti-seize lubricant on the threads.
If you switch the sensors from bank to bank....and then reset the CEL.....and the light comes back on......then.....if the code goes to the other bank.....oxygen sensor is bad.....if the code is the same.....then...oxygen sensor is good.

If you replace oxygen sensors.....I would replace both of the upstream sensors.....so that they will both have the same switching charactoristics. Also....I have read that it is best to buy the Motorcraft brand. You can get the Motorcraft brand sensors for a good price at www.rockauto.com

But, as others have advised.....look for other issues first. I posted some detailed instructions on cleaning the MAF in another post. A search in this forum on "cleaning MAF" should help you find it.
Make sure that you do not have vaccum leaks...perhaps you could have one that is very slight....just enough to trip the one bank's sensor.
A search on "vaccum leaks" will give you an oveload of stuff to look for.

I'm getting the CEL occasionally in my '98 Windstar. I thought it was bad gas as it would run rough for 5-10 seconds then go back to running smooth. This occurred quite frequently until carb/injector cleaner was used. Now it happens less often. Is there a tool I can buy to tell me the trouble code? Hard to nail down the problem as it is so intermittent.

irffri,
You might have considered starting a new thread as we are in a way hijacking this one.

There are several tools available to read your codes. They range in price from $50 to $2000 or more. I bought one for $200 Canadian. (www.codereader.com) You can also go to an Autozone and have them read for free.(so I have been told - we don't have Autozones in Canada). You did not mention the year but all 96 and up use a standard connector and basic set of codes regardless of make and model. You need one that is an OBD11 reader. (again assuming 1996 and up)

Step one is getting the code. Come back here and post the code and we will try and help you.

Thanks for the info and advice. I'll have it checked out.

I started this thread last May, but have finally gotten around to fixing the van. I thought I would post just to complete the thread. I swapped the O2 sensors and the problem followed the bank -- not the sensor (excellent tip, wiswind). After I took the cowl off to look at the back of the engine I could clearly see some sort of bracket above the valve cover that was loose. This bracket held some vacuum lines that were also disconnected. I'm certain the mechanic that did my head gasket forgot to screw this bracket back on after the job... 2 months later is when the CEL came on.

Interresting, the CEL did NOT go off automatically after a week of driving (including highway driving). Stumped me. The guy at AutoZone reset the codes and then the light was off for good. Today it passed the OBD test for Illinois emmisions.

I should have just done a closer inspection last May. I am now over my fear of taking off the wipers/cowl to get access to the back of the engine. Taking all that apart is really no big deal. I read posts some time ago where guys were changing spark plugs from UNDER the van! I cannot imagine as taking the cowl off is so easy.

Thanks for the help... another sucessful DIY repair!