truck performance dropping
Thread Starter
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Senior User
Joined: Mar 2003
Posts: 488
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From: Gettysburg, Pa
truck performance dropping
Seems like my truck is really dropping off, preformance wise lately. Just seems like the engine has to work a little harder then is used to, not to mention the MPG has droppped off over 2MPG. I've recently had my fuel filter replaced, tranny serviced, oil and filter changed regularly, new air filter. This morning I just looked at my MAF to make sure it wasn't dirty, and it wasn't. Nothing has really changed on the truck during this time. Truck is a '06 Screw with a 5.4 and 40,000 miles. Any one have any ideas short of taking it to the dealer???
Junior User
Joined: Dec 2005
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Could be your vacuum hose on the back of your motor. I didn't realize how much of a difference it made, mine popped off while starting the engine one day (2005 f150 5.4), lost brakes, limped to dealership, and they replaced the hose (rear of engine, you can't get to it without taking off the intake cost me $300 labor). Anyway, there is a new and improved version, and when it was changed, my truck was so different I had to get used to it all over again.
Post Fiend
Joined: Mar 2005
Posts: 8,542
Likes: 5
From: Louisiana
a drop of 2mpg is fairly signicant - my first thought was "vacuum" (good catch ketchup). Vacuum systems are simply & cheap for production, but are big head aches when they start going wrong - and they will. I strongly suggest you check you vacuum hoses -trace them from point to point, looking for disconnects, tears, etc. The truck will have to be running so set the park brake and chock the weels. Even unplug lines from junction points to check for a "vacuum" - you should be able to feel it &/or hear the "hisss".
In my experience with Ford trucks, a leaky, disconnected, or connected to wrong port vacuum hose will cause a sudden and very noticable drop in gas mileage. I just found a melted vacuum line on my 2004 F150 after I noticed a 2-3 mpg drop in my gas mileage. Once fixed, I sure hope my mpg returns - I was getting 21+ mpg at 55-60 mph, on a level road with no head wind.
In my experience with Ford trucks, a leaky, disconnected, or connected to wrong port vacuum hose will cause a sudden and very noticable drop in gas mileage. I just found a melted vacuum line on my 2004 F150 after I noticed a 2-3 mpg drop in my gas mileage. Once fixed, I sure hope my mpg returns - I was getting 21+ mpg at 55-60 mph, on a level road with no head wind.
Thread Starter
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Senior User
Joined: Mar 2003
Posts: 488
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From: Gettysburg, Pa
Where do these vacuum lines run to and from...how many are there? I'm only famaliar with the one up on top that connects up on top of the intake and runs down on top of the valve cover on the left side.
