Update to P0171/P0174

Original Post:
A few months ago my check engine light came on and I took it to Auto Zone and they ran the codes and said it was an oxygen sensor. I have replaced that and now the light came back on. Now they are saying no codes are coming up but now it's saying it's running lean on bank 1 and bank 2. And when I am sitting at a long stop light it starts shaking a little forward and backward and the lights flicker and it acts like it wants to die but it only lasts 1 minute or less and then is back to normal and doesn't always do it. What could be wrong??

Thanks!!
Laurie

UPDATE:
Ok, so I took it back in and the codes came up P0171 and P0174 which I found out could mean quite a few different things and not wanting to spend a bunch of money guessing I took it into Pep Boys and they said it was a Lower intake gasket that was causing a vacuum leak. Does that sound like a possibility? I think it will be covered under my limited powertrain warranty through Ford since it's an engine component, so I think I'll just take it into the dealership to save some money. I haven't seen anyone with these codes have this problem with it being a lower intake gasket leaking, does this make sense or do you think they are just trying to make some money??

Thanks!
Laurie

Hello Laurieh,

Your problem is very common. You will see when you get back to the Winstar forum, and find the "Search this Forum" box, (located just above and to right side of the latest message), and type in "P0171 P0174". Go do that, read all the posts about it, then, post your new questions back here. We can help.

Karl

I don't know what year you have but CoachKarl is right on in that those codes are very common in 99 - 2003 Windstars. Autozone probably read those exact codes and misdiagnosed that they were caused by O2 sensors.

You may have some luck getting FORD to pay for some of the repair. Read up on the problem and the related TSB (all in this forum) and go in somewhat informed. It is the Isolator bolts in the Upper Intake that cause the leak and not the lower.

I don't know what year you have but CoachKarl is right on in that those codes are very common in 99 - 2003 Windstars. Autozone probably read those exact codes and misdiagnosed that they were caused by O2 sensors.

You may have some luck getting FORD to pay for some of the repair. Read up on the problem and the related TSB (all in this forum) and go in somewhat informed. It is the Isolator bolts in the Upper Intake that cause the leak and not the lower.


I would like to add that if there is a bad gas knock, then the lower intake gasket needs to be changed. I have seen this before, but it is not as common as the EGR ports getting clogged and the leak of the isolator bolts.

I have a 2000 sel with the same problem. 6 months ago the CEL came on with the PO171 and PO174 codes. Auto Zone recommended the O2 sensors also. After reading in the forum I decided not to swap the sensors. I checked for vacuum leaks but didn't find anything. The van was driving just fine so I did nothing. A couple weeks later it started to die when it idled at a light on the way home from work. I was able to make it home and sprayed the engine again. I found the vac hose boot on the front of the intake to the fuel regulator was dried and cracked. I replaced the line and the van has been perfect since.

*I sprayed under the manifold but no signs of leaks so my fingers are still crossed.

Thanks to the many with great info on this forum!

Fuel pressure regulator vacuum hose gets contaminated with oil, just replacing that will not remove the problem, the upper intake port seals(gaskets) need replacing and the isolator bolts, and possibly the valve cover depending on the part number on it. Oil comes into intake via the valve cover if it doesn't have the proper baffle in it. The P.C.V. hose is how it gets routed to the intake.

The TSB lists the fuel pressure regulator vacuum hose as the first thing to check, and yes that alone can get rid of the P0171/P0174 trouble codes. It did in my case as well. I did replace the valve cover as well on my 2000, but judging by the oil still making it into the intake it does not make much of a difference. I'm sure the isolator bolts and cleaning will be required down the road for sure, but for some the vacuum line may be all that is required to replace initially.