Engine Mechanical problem
2004 Ford Taurus 6 cyl Front Wheel Drive Automatic 129000 miles
2004 Taurus 3.0 FlexFuel engine. When first starting the car in the morning or after it has been sitting a few hours it sounds like a small exhaust leak but after about 1 minute it seems to go away. Car runs great and gets 22mpg. Every since hearing this exhaust noise sometimes the check engine light comes on and the code is P0174/P0171. Lean condition on bank 1/2 which makes sense if I have a exhaust leak. I've tried stuffing the tailpipe to see if I could locate the leak, but I could not locate it. The check engine light never comes on when the car is running only sometimes when restarting the car. I've checked the long term fuel trim and also short term trim too and they are normal when the car is running. It appears that this only occurs at startup. Most emission parts have been replaced except for the cats. Car runs too good for a vaccum leak and I've checked all hoses, intake manifold, EGR, etc. Sparkplugs are the correct model for FlexFuel and the cars idles fine. I used a hose to try and localize the exhaust leak, but there is a heat sheild on the passenger side of the car that prevents an exact location. Have you guys heard of a problem like this before? Most supposed Ford experts keep telling me its a vacuum leak, but I've been unable to find one either in the intake or throttle body or hoses. Let me know what you think. It would be alot of work to pull the exhaust manifolds to try and find the crack or loose hardware.
Fords are bad for vacuum leaks. Look where the pcv line goes to the intake manifold. It is usually a big fitting that a small pipe plugs into and they fall apart and cause the lean codes. As far as the exhaust, try tightening up the manifolds, sometimes there are no gaskets and they come loose on the ends and will do what you describe. Its gonna be a smal leak if it goes away that fast, but that would make me think it is at the head mating surface to heat up and go away so quickly
March, 17, 2010 AT 3:26 PM
PCV and hoses replaced. What is the correct manifold vacuum at idle? What vacuum port is used to make the measurment?
March, 18, 2010 AT 7:43 AM
You will need to tap into the common plenum of the intake, the gauge should read between 15-20 in-hg. Does this vehicle have AIR injection? Maybe there is a leaking check valve that is letting pumped air back into the engine and causing the lean code. Have you checked fuel pressure? Low pressure volume can cause that.
March, 18, 2010 AT 12:12 PM
Manifold vacuum is 18 in-hg and the air injection reactor is attached to the upper intake manifold. No visable check vavles external. Fuel pressure measured at the filter is 30psi when the key is turned. I pulled the positive lead from the battery to reset the learned data and will do the to the floor test to clear and reset the barometric data. Maybe this will help.