I have a 2004 ford explorer with a 4.0 sohc with the codes p0171 and p0174 i already replaced the o2 sensors, i replaced the vacum line going to the pcv, but i also noticed that the lines going from the intake manifold to the evap solinoid when squiezed a black particle would fall off, it look like carbon build up but around the hose not inside should i replace them too or do i look for something else.

SOURCE: Code #P0171 & code #P0174

The most common problem on a Ford with these codes is deteriorated PCV hoses. Check the hoses from the PCV valve to the intake manifold. Pay special attention to the rubber elbows. They often crack on the inside curve and the crack is hard to see.

SOURCE: Code #P0171 & code #P0174

The intake manifold gaskets need replacement as well as the o-rings inside - if you call FORD they should be able to get you the correct parts.

SOURCE: 1999 ford taurus emission reading p0171 and p0174

just tune up ur car periodicly, clean filter. clean ur sparkplug.

Vincent G

• 2363 Answers
• Posted on Aug 31, 2009

SOURCE: I have a 1998 Ford Explorer and I can't get the

You missed two spots.

EGR air passage tube

and

EGR base gasket

The air passage tube get clogged with carbon just like the base of the EGR valve.

It's ten time worst!!!

Get a full bottle of SeaFoam,WD-40 and a snake/wire to clear out this passage.

A home vacuum clean will help speed up the job.

DO NOT forget to get a new EGR base gasket.


Good luck

SOURCE: p0171 and p0174 codes

P0171 System too Lean (Bank 1)
P0174 System too Lean (Bank 2)

If a car has a check engine light on and has P0171 and P0174 codes stored, the most likely cause is a vacuum leak. These codes are set by the car’s computer when it sees too much oxygen in the exhaust. Excessive oxygen readings in the exhaust will set lean codes. This does not mean that the oxygen sensors are defective. It is a common mistake for people to replace oxygen sensors when lean codes are present. Just because the code is related to oxygen sensor readings, it doesn’t mean that the oxygen sensors are bad. If both of these codes are stored this means that both banks of the engine have excessive oxygen in the exhaust. If the oxygen sensors are replaced it’s most likely that the same codes will reappear. It is very uncommon for two oxygen sensors to fail at the same time.

Therefore the most likely cause of P0171 and P0174 codes is a vacuum leak. The source of a vacuum leak can be one of many things. The most common cause of a vacuum leak is a leaky hose. Vacuum hoses over time can become dry and brittle. The rubber deteriorates and can leak causing a vacuum loss. Many times a leaky vacuum hose can be found by listening for a hissing sound. A large vacuum leak can even make the car run rough at idle. In some cases it will not idle without feathering the gas pedal.