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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Why am I getting code # P 0308

I have your vehicle as a 97 Ford Expedition...Is this correct? Reason I ask is that Ford uses Coil-On-Plug and you said "I changed the wires"...Which would mean all eight coils were changed...P0308 is telling you the ECM is seeing a fault on cylinder #8...I would strongly suspect a bad coil for that cylinder...Question; Did you change all eight coils? If not change #8...saailer

I’m happy to help further over the phone at

May 30, 2014 | 1997 Ford Expedition

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Where is the egr valve on a 99 Ford expedition

The EGR valve is in a very difficult spot to work on. If the EGR is bad it will set off the check engine light and make the vehicle run rough or stall at idle. It really doesn't make it run rough while driving or accelerating. What are the conditions when the car runs rough?

Mar 01, 2014 | 1999 Ford Expedition

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Check engine light code P0401 98 Ford expedition

OBD-II Trouble Code P0401 - Insufficient EGR Flow

EGR stands for Exhaust Gas Recirculation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve, an actuator solenoid, and a differential pressure sensor EGR (DPFE). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0401 code means that OBD detected an insufficient amount of EGR. You may notice drivability problems such as pinging (a.k.a. pre-ignition knock) when the engine is under load or the vehicle is at higher speeds. There may also be other symptoms.

A code P0401 most likely means one or more of the following has happened:
The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum

Check it and keep us updated. Hope this helps (remember to rating this free answer).

Oct 13, 2011 | 1998 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

1 Answer

Check engine light stays on the code that keeps coming up is P0401 changed egr valve clened out carbon build up also smell gas when first start not driving and fuel millage not as good car runs good though...

Could be a EGR vacuum issue or temp sensor issue

Common Problems That Trigger the P0401 Code
  • Restriction in the EGR passages, usually caused by carbon buildup
  • Lack of a proper vacuum signal to the EGR Valve from EGR Vacuum Solenoid
  • EGR Vacuum Modulator is defective
  • EGR Temperature Sensor is defective
  • EGR Valve is defective
This is from:

Jan 31, 2011 | 1998 Chevrolet Lumina

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I have a 98 Expedition and the check engine light keeps coming on. I pulled the code (P0401. I changed 3 parts DPFE,EGR valve and the Idle air control valve and it still come on. Any suggestions?

I have several ideas. The code 401 is about EGR flow. While it can be an Electric switch like the DPFE that you replaced, the diagnostics do not included the source of the EGR flow or the Backpressure pipe which the vacuum lines from the DPFE operate from.

In short, it is about plain old low tech plumbing. The EGR passage gets its flow from a groove under the Airhorn. If the groove is plugged you need to remove the Airhorn and its gasket and scrape the groove clean. It has about 8 bolts, a $10 gasket and you need to disconnect the Air Intake and a few Electric wires.

Connected to the DPFE are 2 high temperature Vacuum lines. If the tip above does not help, then you need to check this plumbing pipe out for holes. In particular, there is a irregular joint on this pipe which can separate and vent. It should not vent. This will throw off the closed system and generate Error Codes. One end goes towards the exhaust and the other to the EGR.

Finally, do not forget to clear the computer. Old problems stay in the system for 25-35 Startups. I hope my solution has been very helpful to you.

Jan 05, 2011 | 1998 Ford Expedition

3 Answers

1998 ford escort code P0401 I need to know what this code is for. Thank You.

This code is an EGR code for insufficient amount of egr. It could be that the egr tube is clogged or the egr itself is bad or there is not enough vacuum to open the egr properly. There is also a sensor called the DPFE(differential pressure feedback egr) is faulty.

Jun 25, 2010 | 1998 Ford Explorer

1 Answer

1998 ford expedition blinking overdrive light

This blinking light indicates a problem. You will have to have it scanned for trouble codes to find out
what it is.

Mar 29, 2009 | 1998 Ford Expedition

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97 tracer P0401 code won't go away

the light may have nothing to do with the previous fault
run the fault codes again

Sep 11, 2017 | 1998 Ford Expedition

2 Answers

I'm getting an engine check light, the OBD-II is P0401.

try to clean out the tubes, it is very common for the tubes to get clogged up with carbon, also check for any breaks in the vacuum lines

Oct 13, 2008 | 1998 Ford Expedition

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