Question about 1998 Ford Expedition

1 Answer

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?

Posted by 256mbw on


1 Answer


  • Level 1:

    An expert who has achieved level 1.


    An expert whose answer got voted for 2 times.

  • Contributor
  • 1 Answer

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

Posted on Jan 12, 2009


Add Your Answer


Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

2 Answers

2000 Expedition with 4.6L runs rough for a while

Sounds like a cold start problem from the description. You should check the coolant sensor circuit and the idle air control motor. Make sure the coolant level is full or the coolant sensor will give a false reading. Check the idle air motor and throttle plate for varnish and sludge and clean with a carburetor cleaner listed as oxygen sensor safe. Other checks should include condition of filters, plugs, wires and vacuum lines and line routing. If you have a scan tool, the data stream would be the fastest and easiest way to check the sensor circuits.

Sep 09, 2014 | 2000 Ford Expedition

1 Answer

Vacuum Issue on 2006 Lincoln Zephyr

Problem Description and Possible Solution
A vacuum leak from the PCV grommet. A vacuum leak can cause the Check Engine Light to illuminate. The molded rubber hose connections may crack and collapse, causing the vehicle to run roughly. A damaged PCV hose will require replacement.

Problem Data
Average mileage: 137,860 (98,300–203,000)
17 model years affected: 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007

Jan 21, 2018 | Lincoln Cars & Trucks

1 Answer

Car stall 1998 toyota corolla, replace cam shaft sensor, crank shaft sensor, could it be the main fuse box

The Year 1998 Toyota Corolla engine will stall due to:
Spark plug faulty
High-tension cord faulty
Ignition problems:
• Ignition coil
• Igniter
• Distributor
Incorrect ignition timing
Vacuum leaks:
• PCV line
• EGR line
• Intake manifold
Throttle body
• Brake booster line
Incorrect valve clearance
EFI system problems
Engine overheats
Low compression

Feb 11, 2014 | 1998 Toyota Corolla

2 Answers

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 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)


Dec 02, 2011 | 2002 Ford Expedition

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...

If you have a manifold leak that will cause a MASSIVE vacuum leak and make it run rough at idle only. Look at your short term fuel trims with a scanner, if they are way negative you have a vacuum leak. Fix the intake manifold leak and that will fix your problem.

Oct 06, 2011 | 1998 Ford Expedition

2 Answers

When i start my 1998 Ford Expedition, it immediatley dies out unless i step on the gas right away.. but once i let go of the gas pedal, it dies right away... what could be the problem? please help...

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.

Aug 29, 2011 | Ford Expedition Cars & Trucks

1 Answer

When I slow down and my engine will vibrate.

Rough Idle usually indicates a vacuum leak. You may have to feel along the lines that are routed in the back. My expedition has a small line that is routed from the PCV valve to the back of the intake where it goes from a small hard vacuum in to a reducer connection. This connection crumbled. The vacuum lines deteriorate over time. Some may not look bad, however they are like a sponge. sucking air the entire length.
I use a propane torch (not lit). Turn on the valve and trace the vacuum circuit. If you have a leak, the engine will rev up slightly when the torch passes the leak.

Aug 26, 2010 | 2006 Ford Expedition

4 Answers

How to fix problem with cod P1506 Ford explower 1998

Hello! The Idle Air Control (IAC) is setting P1506...Idle is to high...Other problems can cause the idle to over speed...It isn't the IAC in many instances...A vacuum leak is #1...The vehicle has some years on it...Go over the vacuum lines and look for weak collapsed lines, broken, or poorly seated...A defective PCV valve is #2...If it hasn't been changed in awhile it's due...Base idle should be 780 in neutral...If # 1 and #2 prove to be OK I'll take it from there...


I’m happy to help further over the phone at

Aug 19, 2010 | 1998 Ford Explorer

1 Answer

What could be a vacuum sound in a 06 chevy trailblazer coming from the engine

It could be numerous vacuum lines. Check the PCV valve and the vacuum line from it to the end, Sometimes these will get dried from the heat or can collapse inside. Also the line could have a crack or hole that can't be seen. While the engine is running, listen for where you think the sound is coming from. This will put you in a general area. Then feel and move the vacuum lines within that area. If you hear the vacuum sound get louder or faint then you have narrowed the line down.

Mar 01, 2010 | 2006 Chevrolet Trailblazer

Not finding what you are looking for?
1998 Ford Expedition Logo

Related Topics:

681 people viewed this question

Ask a Question

Usually answered in minutes!

Top Ford Experts


Level 3 Expert

85239 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22485 Answers

Jeffrey Turcotte
Jeffrey Turcotte

Level 3 Expert

8984 Answers

Are you a Ford Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides