Hello, all! I've run into a dead end in my attempt at fixing my 2007 F150 4.6 (105,000 miles) so I figured I'd give this forum a shot.

A while back, my engine light came on and I noticed a bit of a rough idle. I had the auto parts store run a diagnostic and they said "multiple misfires". I changed the spark plugs.

The engine light came back on (unplugging the battery to reset the computer and turn off the light didn't work ) and the rough idle was still there but not as bad. Ran the diagnostics again and they said "MAP sensor". I researched the MAP sensor and the internet said my truck didn't have one of those. I figured they must have said MAF sensor since my truck did have one of those and the symptoms of a bad one were similar. I changed that.....to no avail. Engine light stayed on, rough idle, and poor fuel economy.

I run diagnostics again, they say MAP sensor. I call the dealership and they say they can't find that part for my truck. I dig deep into the research and find out that my truck does not have one, only the 5.4s do. Turns out my EGR valve can send that code. So, I prepare take mine off and clean it out to see if that'll do the trick....when I notice a small broken hose behind the valve. I take it to Advanced and they fix it for free.

Engine light goes off (and has remained off) and I think life is good.....until I notice the rough idle is still there. Poor fuel mileage (16/17 hwy with the 4.6 isn't good) as well. At 100k I changed the air filter and the fuel filter so I can't figure out wth is going on.....until I notice a small broken line under my air filter. It's the one just below center in the middle of this picture. Could this be the root of my problem?

Any help would be greatly appreciated. Thanks!
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Where does that hose go to?

 

Im a 5.4 guy so bear with me. Does the 4.6 have individual coils or just one?

 

My 06 4.6 has 8 individual coils. One on each plug.

I can't tell what line/hose your talking about? Can you add an arrow pointing to it in the pic?

 

replace the coils.

 

DON'T REPLACE THE COILS! Clean the contacts on the coils and put new boots and springs on them first! Much cheaper and fixes a misfire 90% of the time if the plugs are new and a misfire is in fact your problem. People stop wasting good coils please.

 

After doing al that did you go through the re-teach (Disconnect battery, ground cables together, ad nauseum?) If not, it's still using old maps from when there was an issue to try to run the possibly fine engine.

 

I can't see the broken line you are referring too in your picture. Can you circle it or point it out?

I had a rough idle problem which turned out to be a vacuum leak at the back of the throttle body where the vacuum hose from the vacuum brake booster connects to the engine. It stumbled across it when I was checking my EGR valve. It looked like the vacuum hose was connected to the nipple, but when moved it, I found it was loose. May not be your problem but check yours (and other vacuum lines) just in case.

How are you calculating or reading your mpg's? I'd settle for 16-17 mpg hwy as I only get 14 mpg hwy (calculated between gas fill ups, not a computer read out) with my 2006 4x4 stock 4.6 3.73 gears and about 75k miles.

 

Rough idle is due to either an ignition misfire, or air/fuel mixture issues. Air entering the intake that is unmetered will throw off the fuel/air mixture "maps" used by the PCM (powertrain control module). The PCM uses various sensors to determine the correct air/fuel mixture for a given RPM. The MAF (Mass air flow) is one of the main sensors used to adjust the fuel to air ratio based in the amount of air the MAF detects. The TPS (throttle position sensor) also is used for this adjustment.

So, if you've replaced the MAF, checked and repaired any and all potential air leaks (hoses, air filter box and tube to throttle body), I'd suggest you remove the throttle body and clean it. Poor or rough idle can also be due to carbon build up on the throttle body plate. There are several threads on this subject on this site. Its easy to do, just be sure to use a throttle body cleaner, and not gasoline or carb cleaner, as they can remove the coating that is on the throttle body plate. Then remove the battery cables, reinstall, and allow a 20 minute ride around town for the PCM to "re-learn".
If you still have a rough idle, you could have a bad coil or two, but that should set a new code (each coil has a specific code it sets). On the V6's, they have only one coil pack, but the V8's have an individual coil (COP - coil over plug) per cylinder.

 

I cannot see where it's supposed to go. There doesn't seem to be another end near it, but when I trace it back towards the firewall, it goes inside the side of the engine compartment beside the steering column.