I have a 98 lincoln navigator I recently pulled the codes p0171 and p0174. Whenever I accelerate it makes a loud hissing noise and it also sounds like alot of air is either getting sucked in or sucked out like a propeller. I recently did some work on it such as replacing the sparkplugs which I had to remove the fuel lines which were connected to the fuel injectors, had to remove the throttle body to get to the idle air control.
Lean fuel condition could be caused by one of the following below: 1. Vacuum leaks
2. EGR and PCV valve.
3. Low fuel pressure.
4. Dirty fuel injectors.
5. Mass Air Flow Sensor.
6. Oxygen Sensor.
January, 13, 2011 AT 11:12 PM
You have a bad vacuum leak. Follow the hissing noise to it's source. Common failure points are the rubber connectors at the intake manifold and large rubber hoses for things like the PCV. It may not be visible with the engine off because the vacuum sucks the hole inward and it returns when shut off. If you move your hands around the engine you will hear the noise change when your hand gets between your ears and the leak.
January, 14, 2011 AT 4:29 AM
Here's the thing though when it is in park or neutral and I have someone step on the accelerator it revs the engine like normal. It only makes the loud hissing noise and wind sound when I am in reverse or drive.
January, 14, 2011 AT 1:02 PM
It's likely just louder then because that; s when vacuum is the highest. Check under the dash and make sure the leak isn't under there at the parking brake release also. That would only activate in drive or reverse.
January, 14, 2011 AT 10:47 PM
Okay so I checked for a leak under the dash and where the parking brake release is but still nothing. Something else came up though my catalytic converter underneath the driver side was glowing red.
January, 14, 2011 AT 10:50 PM
That's the fuel mixture doing that. You need to find the cause of it.
January, 14, 2011 AT 10:58 PM
Where would be the best place to start from
January, 14, 2011 AT 10:59 PM
Follow the noise.
January, 15, 2011 AT 12:14 AM
Ok I located that the noise is coming from underneath the engine which looks to be around where the crankshaft position sensor and timing chain would be. Would those be making a clicking noise and preventing me from accelerating at my full speed when I try to floor it
January, 15, 2011 AT 3:42 AM
I have no idea what you have now. There is no vacuum down there or anything else that would cause lean codes.