i have a 99 F150 4x4, 4.6L w/128,000. It has had a miss in it whenever at a stop (either in park or in gear, more so in gear). It finally threw and Air Metering code last week and i replaced the MAF. It idled so smooth after the install. But this morning the miss was back. Not as bad as before, but it was there. The plugs and wires are about 1.5-2 yrs old. I was just woundering about checking for VACCUM LEAKS. Where are All the VACCUM LINES at that should be checked. AND are there other AREAS other than Vaccum Lines that should be check as well.

About a month ago, my MPG took about a 3-4 mpg decline. this is city driving and i used to get around 15, but not it is around 12. and ideas...thanks guys.

 

i hooked a timing light to the plug wires to check the sparks and not all of them sparked at the same speed.. some were faster than others. is this normal. if not, is it a plug problem? or wire or coil pack problem? or something else that i would rather not know about...if anyone has any ideas, lets hear them...thanks guys

 

Is the CEL still on? What is/was the DTC that you got? With what you said about the timing light, I would be suspicious of the spark plug wires or even the coil packs. When you changed the plugs/wires before, what brand parts did you use? It may be time to do this again. As for vacuum leaks, there is a elbow at the rear of the intake manifold that I have read about rotting through and causing problems. I don't remember the details of the associated symptoms with it. Good Luck!

 

the last dtc was an air metering problem so i replaced the maf..i used autolite plugs the last time...i dont remember what wires i used...what type should i use for the wires..from what i have read i need to use motorcraft plugs...what is the life exptantcy of the coil packs.

 

What is the actual DTC number?

These trucks in many cases seem to be partial to Motorcraft parts for plugs and wires. The heat in the engine compartment as well as the voltages that are generated can wear a coil out. There is no rule of thumb that I am aware of on coil life expectancy.

 

If you determine that it is your coil packs at fault, consider our 4.6 Screamin' Demon Coil Packs:

http://www.performancedistributors.c...50ignition.htm

 

i am not sure what the exact code number was, but it did say "Air Metering". something along the lines of faulty or bad air metering i think...but it went off a day or two later, but i still replaced the maf. it has thrown a code saying that "bank one was too lean"..and i went through the whole egr deal with it as well.. changed the valve, dpfe sensor, but the ports were clogged up. but i never really could tell a difference in performance after fixing that problem..it has done this for a long time...but hopefully ill figure out one day how to make this thing run and idle as smooth as it should...

 

Check the pcv line at the manfold. The elbow there is bad about rotting & causing a leak. I had a vacumm leak on my truck behind the battery. It was hard to find & it was causing my air vents to go to defrost when I put my truck under a load. It was a split in a hard line where it went through the dash.