bkoon

Hello all I have a 1998 Ford F150 4.6L Triton V8 with the FX4 package. As of recent I have noticed my truck tends to idle roughly every so often that I start it up and after longer trips but will run fine once I get going. I take care of my truck like its my baby. I've done everything to it that I can without getting into the engine such as replacing spark plugs, wires, KN air filter, new ignition coil packs, change oil every 5000 with best products, etc the basic tune up stuff every one should do. This truck only has 118,xxx miles on it as it sat in a barn for around 4 or 5 years due to the previous owner being in the military. I have been trying to search for the cause of this problem but cannot exactly seem to pinpoint it myself. One unusual thing I've noticed also is that when I run the air either hot or cold when my RPM's get high, when I go up hills or punch it, the air switches from vent to dashboard(defrost). I talked to someone who said this was most likely a vacuum leak. Maybe there is a correlation between the two? I'm not exactly sure. I read online my idling problems may be from a cracked PCV elbow? I cleaned out the IAC valve also about two months ago to see if that helped. If anyone has heard of anything similar to this any help would be appreciated! I am willing to try anything myself as long as it doesn't involve tearing the motor apart! Thank you! If you have any further questions or info you may need please feel free to ask!

Marc D

Yes a vacuum leak or intake manifold leak is probably your issue. Start by looking at all your hoses on the motor and your PCV valve. If they are stiff or cracked replace them. Look carefully around the intake manifold for broken lines. Also clean your MAF sensor using only approved spray.