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2006 F150 P0174 after replacing coil for

17K views 3 replies 3 participants last post by  craig89lx 
#1 ·
I have a 2006 F150 5.4 liter and at 100,125 miles my Check engine light came on after a heavy acceleration.
My boss let me use his diagnostic scanner and read the p0308 (cylinder 8 misfire) code.

Today I swapped the coil AND plug from cylinder 8 with cylinder 1 and disconnected the negative battery terminal to clear the CEL. When I started the truck they engine was shaking and running really rough. At this point I assumed it was the the coil from 8 so I went ahead and spend the 47 bucks for a new coil. I put the cylinder 1 plug and coil back in its place and put the new coil on cylinder 8 but the truck it shaking just as bad.

I thought maybe the computer needs to adjust so I drove it around. The truck barely ran and the CEL came back on so I pulled into Auto Zone and the new code it P0174 (lean bank 2) The guy at the store said a vacuum leak and that's what I am also reading on the internet.
Did I knock something loose or break a hose?
Could it be a way over due fuel filter?
Could it be the fuel injector from cylinder 8 that through the original misfire code?

I had to call out of work using 2012 vacation time and I really cant afford to go tot he dealer which is why I was trying to fix the problem my self.

Can anyone make suggestions?
 
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#2 ·
Update

I bought 8 new plugs and MAF cleaner. So far I replaced the 4 plugs on the problem side (drivers side) since that's where the misfire and the lean code point. At the same time I cleaned the MAF with the cleaner and the rough idle and shaking is fixed and the lean code has not came back. Unfortunately I didn't try the MAF cleaner alone so I cant say what the real fix was.

Now Im going to do the other 4 plugs and then the fuel filter. None of this stuff was ever done.

My injectors are noisy and is it worth replacing all 8? I found a code for advanced auto that will give me 40% off but they don't have them in stock so I didn't buy them yet or should I just dump some injector cleaner in the gas tank?

Also the plugs I got today are not the same motorcraft plugs I pulled from the truck but they are outside so I cant get the codes right now to see which are the more recent codes but I am using anti seize on the threads and it looks like a bitch to get to the cylinder 4 (rear passenger side)

I am the farthest thing from an auto mechanic but maybe this will help some other person some day as 99% of the google results suggest a vacuum leak for the lean code and I don't think that was my problem.
 
#3 ·
My son's 2006 F150 5.4l shaking at Idol, tranny shuttering at 40MPH. found one of the wires that cover the spring going to the plug had a pin hole in it, wrapped it with electrical tape, both problems went away. the real answer is to replace the cover, of course, but this was a test and it worked.
 
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