*HELP* Codes PO171 & PO303

[taranmalhi]

Hey guys,

Check engine light came on earlier today while I was driving. Truck started idling real rough, almost as if though it was bogging out. I went to Princess Auto, bought a handheld scanner. The scanner read codes P0171 (which is Bank 1 is running too lean), also P0303 would pop up a short while after (which is Cylinder #3 misfire). So I already swapped the coils from one cylinder to the other, misfire still occured. Then I changed the spark plug in Cylinder #3, misfire still occured. I tested all of my injectors and got an average reading of 13.5 ohms all the way across. I've tried eliminating the whole spark & fuel issue. Now all I have left is air. Whenever I tend to accelerate, I hear almost a hiss coming out (possible vac leak). I was wondering if anyone has dealt with something similar.

I'm thinking about changing all the COP's to MSD coils, plugs to E3, brand new injectors, MAF sensor, O2 sensors.

Before spending good coin in maintenance, I wanted to know of which locations to check for vac leaks, where are the common places to look for?

Really stuck here on this one! Motor is 4.6 Litre V8.

Thanks!

 

[polizi212]

Track down and make sure you have no vacuum leak as that will give you a lean condition...This should be your start!

 

[jcat9]

when you say you swapped the coils, do you mean you swapped the #3 coil with a diff cylinder and then the misfire still occurred on #3?

I agree with polizi212, this screams of a vac leak, maybe even a PCV issue.