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Discussion Starter #1
my car has been running great all until about a week ago...
i started the car one day and it began to idle hard and run poorly when pressing on the throttle, it would kind of clear up on WOT but right back to running rough as soon as i let off the pedal. when the car gets to operating temperature it clears up alot of it but i can still feel the problem.
A few different people have said it is more likely an O2 sensor gone bad so ill try that first, but how do i know which one it is? i realize i should replace them all but that will need to wait a month or so. the computer isnt throwing any codes...
 

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keep in mind that oxygen sensors are expensive to just be throwing them randomly at the car to try to fix a problem.....dont get me wrong, it wont hurt to get new upstream O2 sensors (the ones after the cats do not affect how the car runs at all)

first try cleaning the MAF and check/replace your spark plugs/wires as necessary......regular maintenance is key here, to isolating your problem
 

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the MAF is cleaned regularly, the plugs and wires and all new, not even 6 months old. the fuel filter has been changed recently as well, the air filter is also new. its been maintained pretty well....
 

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Is it making any noises? A bad IAC (Idle Air Control) valve will sometimes give a high pitched whining noise when it is going out. If this is the case then you can test it by taking this procedure:
http://www.ford-trucks.com/article/idx/0/170/article/Ford_Explorer_IAC_Fix.html

The voltages in this artcle may not be applicable to your vehicle, but I will look to see what the correct voltages are when I get home in a little bit.

The other think to check is the TPS. Has anything been done to the intake/throttle body lately? (http://www.blueovalchips.com/tech/throttlepos/throttleposadj.php). One of my T-birds just wouldn't run right until I got the voltage down to 1.0 V. . . . .The previous owner had been "playing" around with things when I bought it and he wasn't very good at "playing" :)
 

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hmmm thats another symptom... yeah it was making a loud "whining noise" then one day it stopped, now this.....
you can smell a raw unburnt fuel stench and see large puffs of smoke when pressing hard on the throttle.
 

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I wouldn't be thinking about the oxygen sensors causing the problem, especially if it runs crappy right at start-up AND when it's cold. The 02's aren't used during start-up and open loop, which is the mode in which the car runs for the first few minutes of operation. If you've got everything pretty good (plugs, wires, filters, etc.), then I would say the likely problem is your MAF. Just because it is clean doesn't mean it's working properly anymore, and the problems you described go hand-in-hand with a malfunctioning MAF.
 

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LowLyfe83 said:
hmmm thats another symptom... yeah it was making a loud "whining noise" then one day it stopped, now this.....
you can smell a raw unburnt fuel stench and see large puffs of smoke when pressing hard on the throttle.
I think that the whining could be the IAC. I will look up the voltages, just give me a bit. The smell of unburnt fuel means that it is running rich and the running rich can cause it to run as described. Is the smoke that you are seeing white or black?

white=oil
black=unburnt fuel
 

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All voltages/resistance readings are as posted in the article for the motor listed in your profile. :) Hope this solves the problem. Let us know.
 
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