Question about 1998 Ford Expedition

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Multiple vacuum problems. Now receiving P0401 and P0308 codes.

1998 Ford Expedition 5.4 Triton. I have replaced numerous vacuum lines, such as the PCV line, and others due to holes or tears. Now the engine runs rough again. Codes indicated are P0401 and P0308. Any suggestions?

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Spray carb. cleaner on vac lines while running. engine will change rpm when sprayed near vac leak

Posted on Jan 12, 2009

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2000 Expedition with 4.6L runs rough for a while


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Replace pvc vacuum lines


If you have the 4.6L or the 5.4L engine, they are notorious for the PCV line to get a hole in it at the elbow that goes into the back of the throttle body. It is not rteal easy to get to, but it is not hard to change once you get your hands on it.

You can get the part from the dealer or you can order it from fordparts.com. It depends on if your Expedition is equipped with a heated PCV or a non-heated PCV. The base part number (6C324) is the same for both, but the rest of the part number (not shown) is not the same and they are NOT interchangeable. If you are not sure how your vehicle is equipped, it is best to contact the dealer and give them your VIN to look it up with so you can be sure and get the correct part. The hose assembly for the heated PCV system is over twice the cost of the other one. (See picture below)


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1 Answer

My 1998 expedition with the 5.4 triton runs rough at idle but clears up when driveing down road I know I have a manifold leak and the previous owner said it was a coil pack, however after I had advanced...


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The age of your vehicle also guarantee's a vacuum leak. It may sound silly but the truth is rubber grommets, and hose's shrink and dry out over time and the harsh environment under the hood makes it worse. Check all vacuum lines and fittings attached to the intake manifold, valve covers (pcv valve), and be sure to check for a vacuum fitting on top of the intake just behind the throttle body. Does it fit tight in the hole? You can seal loose fittings with a high-temp RTV (Red) silicone sealant/adhesive. Several small leaks add up and your engine, heat/AC, and transmission will be all to glad to tell you about it.

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When I slow down and my engine will vibrate.


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Guru.............Saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

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