I have a 2006 ford Taurus that idles rough. i have replaced all 4 oxygen sensors and all 6 spark plugs. i did not right down the all of the codes. there was a lot of them. some of the descriptions were pointing to the o2 sensors. They also stated the plugs were misfiring. like most other people, when you have the car in motion, there are no issues. i am waiting for the check engine light to come back on so i can get all of the codes. i have heard of the em-famous hissing sound coming from under the hood. could this be the hose that goes to the egr valve or the pcv valve?
SOURCE: PCV valve? IAC valve? Sparkplug wire? Throttle body? Vacuum hose?
the most common causes are plug wire, plug, vacuum leak at intake, fuel injector failure and last no/low cylinder compressio.
SOURCE: I have a 1999 oldsmobile
fuel pressure regulator on the fuel rail is probably it or the egr valve is stuck open allowing burnt fuel to flood the intake, im leaning towards the fuel pressure regulator because the o2sensor is probably reading rich or if its reading lean then i would choose the egr valve . good luck
SOURCE: 2006 pt cruiser idles high with no pcv valve hose connected
Replace the PVC valve, it's probably clogged.
SOURCE: My 2002 Ford Taurus will shutter and die when
the idle air control valve is responsible for engine idle.
this is a common failure on ford's. but I don't think yours is bad because it does idle high befor it dies.
you stated you had codes p0171 and p0174 these are lean codes for bank one and two, you said you found a vacuum leak and repaired it, the vacuum leak was mostly likely the cause of the lean codes, however the pcm has calibrated the fueling stategy for this lean mixture, what you need to do is erase the KAM "keep alive memory" this is done by unhooking the negative battery cable for 60 seconds, this is the only way to erase the KAM the $6000.00 machine I use wont even do it.
once the KAM is clean the computer will go into a relearn state and all operating values will be adjusted for the vehicles current condition, during this relearn session the vehicle may have some driveability issues (low or high idle, stalling, poor fuel economy) the relearn should complete within 10 minutes of idling and then 10 minutes of driving.
good luck and keep me updated
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SOURCE: My 2004 Ford Expedition 4.6l has a rough idle and
well i'm sorry that you got the miss information here on fixya. because all internal combustion engines need a pcv valve to operate properly.
now the information you got first is correct and pcv valve can set false codes like o2's and lean bank conditions also can cause you vechile to run or idle rough.
no there are a few different styles pcv valves and some times don't look like your convetional pcv. some are heated in different ways either by coolant ( witch look like a conventioanl pcv but with a coolant tube around them) then electricaly heated and they don't look like them at all. but one thing that has to stay the same is the pcv valve has to ventilate the crank case and will be found somewhere on or near the valve cover because it is the easiest and most accessible point of the engines crank case area. so i would look for that and usally on that vechile it is on the passanger side valve cover in the middle.
with that said and seeing you did all those repairs i would go right for that as my next step. but there is other thing that cold cause this issue like leaky injectors and is almost more likely becuase of the o2 sensor code and backfire. do you have the code # so i can look it up and best assist you?
see vechiles are hard to fix over the computer as i am trying so if you have any more question/info about this issue please ask and i will be glad to help.
Testimonial: "Cool thanks, i'll check the pcv valve/ line going into the back of the intake, if that doesn't work i'll go for the codes again....thanks again...."
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