Vacuum Leak under load?
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Vacuum Leak under load?
Good morning everyone! I have a big lack of power from my 1998 Expedition 5.4L. So far in trying to diagnose this problem I have replaced the plugs, replaced all O2 sensors, replaced the exhaust manifold studs added a superchips power tuner and still nothing. What is going on, is when I floor the truck, there is essentially no power. I mean dont get me wrong it does what it needs to do, but for a 5.4L it is not even close to what it should be doing. I drove a friend of mines 1997 with that same motor, and there is no comparison. And his is stock as well. Anyway, when I go to floor it, I get what sounds like a vacuum leak from the front right somewhere in the engine compartment. I have heard from previous reads to check the PCV hose for a cracked elbow, and I have checked this, but have found nothing, HOWEVER, I found a hard hose that goes around the back side of the throttle body, so all I can do it follow it with my fingers for as far as it goes, and I cannot FEEL any damage. Should I be checking anything else? Thanks!
Fleet Owner
Joined: Apr 2008
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From: 0,0,1
A vacuum leak unless it's a good size isn't going to rob you of all that power. Also, a vacuum leak will give you other problems like running rough, high idle, or stalling, and you haven't mentioned any other symptoms. I would first check your fuel pressure and make sure you're getting enough fuel to feed the engine.
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From: Billings, Montana
Fleet Owner
Joined: Apr 2008
Posts: 24,322
Likes: 5,132
From: 0,0,1
You need to borrow, rent, or buy a fuel pressure gauge and hook it up to the fitting on the fuel rail going to the injectors.
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