1999 Ford Contour Engine Codes P0171/P0174

SFC K

MEMBER
1999 FORD CONTOUR

Other Category problem
1999 Ford Contour V6 Front Wheel Drive Automatic 93,000 miles

I am having issues with my Ford Contour SE with the 2.5 DOHC that has 93,000 miles on it. One morning on my way to work I went out to start it and it started right up, but as the idle dropped it started to idle erratically and then eventually died. I started it up and feathered it to keep it running and in gear it idled fine. I drove it to and from work with out any issues. This happened for two days. I went ahead and replaced the fuel filter and the spark plugs and the rear Oxygen sensor. After replacing these parts it ran great for a couple days. Then it started acting funny again and the engine light came on with the codes P0171, and P0174 which mean it is running lean, banks 1, and 2. Should I replace the other two Oxygen sensors now or is it is something else that is causing the problem? Note that when there is a constant load it runs fine. When it is in park or at a stop sign the RPM’s drop way down almost to the point of stalling out. I also live in MN, and it has been really cold.

2 Replies

FLEXY5

MECHANIC
512 POSTS

Do NOT replace the oxygen sensors. It is a common misconception that these codes mean there is something wrong with the oxygen sensors. They are working fine. What you should be looking for is a major vaccum leak. Most likely the PCV hose has collapsed. This allows the engine to suck unmetered air into the intake making the engine run lean. Find the vaccum leak and you will solve your problem.