Hi, all. I rarely post in any forum, but wanted to share my recent experience fixing my 99 Expy. Over the last year, it had progressively gotten worse. The problem started with intermediate sputtering during acceleration and culminated with consistently poor throttle response and the engine regularly dying during driving. It didn't pop codes until very late in this process.

I know there are pieces of this problem posted all around, but I started this thread to build a more comprehensive look.

Like most, I'm a busy guy with little time for troubleshooting engine troubles. I have a background in aircraft maintenance, but that doesn't necessarily translate well to autos. I finally carved out some time over the past month. Using this forum among others for research throughout the troubleshooting, I finally fixed the issues. I hope the following may shorten the time spent for someone else.

Here's my maintenance journal:


1999 Ford Expedition 5.4L
125,000 miles

Rough idle, Sputter at acceleration, eventually dies out
Fault Codes:
P0171 - System too Lean (Bank 1)

ACTION:
Replaced MAF sensor

RESULT:
No change… still ran poorly. No codes.

ACTION:
1. Replaced PCV Line
2. Replaced DPFE
3. Removed and cleaned Throttle Body
4. Replaced Idle Air Control

Not included above, but noteworthy is that the air and fuel filters were new. With the TB off, I took the opportunity to pull fuel rails, inspect fuel injectors, and replace spark plugs and coils.

RESULT:
Ran tons better, but still had a rare sputter.
Fault code:
P0401 - Exhaust Gas Recirculation Flow Insufficient Detected

ACTION:
1. Replaced EGR Tube
2. Replaced DPFE Hoses

RESULT:
Ran worse than previous fix, but did not completely shut down like original symptoms. While the regression was unfortunate, I got new codes that could mean progression towards a complete fix.
Fault codes:
P1409 - EGR Vacuum Regulator circuit malfunction
P1121 - Throttle Position Sensor Inconsistent with Mass Air Flow Sensor

ACTION:
1. Replaced TPS
2. Replaced DPFE Hoses (Not happy with previous brand fit)

RESULT:
First test drive had some issues at idle including shutting off twice. No associated codes. Drove 1 mile.
Second test drive had zero issues. Drove ~5-7 miles at varying speeds below 35 MPH due to speed limits.

ACTION:
With no codes, took the opportunity to replace O2 sensors:
Replaced 3 of 4 O2 Sensors.
Could not access forward passenger side

RESULT:
Cranked and let idle. Several sputters. Eventually died out. However, no change expected for this action. Several test drives resulted in engine consistently dying.
Fault Codes:
P1121 P - Throttle Position Sensor Circuit Intermittent High Voltage (Pending)
P0103 – MAF Circuit High Input

ACTION:
Tested wiring on MAF Sensor. DC and both grounds tested good. MAF voltage wire tested good, but I considered this somewhat inconclusive due to intermittent nature of problem. I began to wonder if I had missed a port in the throttle body or spacer. Therefore, I pulled the throttle body and spacer, inspected, and cleaned again. No apparent blockage found.

RESULT:
Same issues as previous.
Fault Code:
P0103 – MAF Circuit High Input

ACTION:
Replaced MAF Sensor (again).

RESULT:
Ran perfectly. No issues or codes after one week of in-town driving.


BOTTOM LINE:
Parts for Mechanical Issue Actual/Dealer
1st MAF Sensor $81/$205
PCV Line $30/$30
Idle Air Control $43
EGR Valve $73
Throttle Position Sensor $41/$68
DPFE Sensor $56/$109
DPFE Hoses (2 sets) $12
EGR Line $52
2d MAF Sensor $155/$0
Tools/Cleaners $35
Total $578/$412

Parts for Upgrades
Volant Air Intake $272
Total $272

Parts for Scheduled/Preventive Maintenance
4 x O2 Sensors $178
8 x Coils $200
8 x Spark Plugs $41
Total $419

Total Expense $1213
Actual Troubleshooting $578


COST COMPARISON:
Ford Labor Rates: $95/hr
Labor times are estimates. I do not have a labor rate manual.
This is likely conservative as the following assumes only bad parts were replaced (i.e. no “just-to-be-sure” replacements).

Diagnostics 0.5 hours
MAF Sensor Replace 0.5
Throttle Body Cleaning 1.0
Throttle Position Sensor Replace 0.5
DPFE Sensor/Hoses Replace 0.5
PCV Line Replace 0.5

Total 3.5
Labor Cost Saved $332.50
Dealer Parts $412
Total Dealer Cost $744.50

LESSONS LEARNED:
1. “Brick and mortar” auto parts stores (good experience with O’Reilly) are better than online. If you get a bad part, you don’t feel stuck with the old one.
2. If you have to use online, rockauto.com is the way to go.
3. Lesson relearned: A good combo flashlight/magnet/finger retriever tool is an absolute requirement for auto maintenance.
4. Lesson relearned: Check and recheck all sensor attachments after maintenance. I twice popped a code for Inlet Air Temp due to leaving the sensor unhooked.

PERSPECTIVES:
1. Education – Shade tree experience continues to be invaluable assuming you have the time and patience to persevere. I learned tons relative to OBD codes, emission systems, and electrical troubleshooting. Tough to put a price on self-education.
2. Piece of mind – I am always more content having done the work myself. It can be challenging to find a truly trustworthy, albeit well-intentioned, mechanic.
3. Money x2 – My experience may save others and me money in the future.

Best of luck to anyone working this issue!

 

Very well done. Great info for others. Could ha e saved some $ not buying all O2 sensors, ESP back two.
Reps sent.

 

I have a question, what drove you to replace the EGR Tube? I am having an issue with my 2003 Expedition. For whatever reason the smaller of the two tubes coming off the EGR tube and lead to the DPFE keeps blowing off. I have replaced the EGR valve, the DPFE and the Solenoid. Yesterday I even took the intake manifold off and found some carbon and was hoping that was my issue. After assemble I took it for a test ride and it blew it again. It almost seems like there is a blockage but I would have thought that the EGR tube is wide open. Any insight would be greatly appreciated.

Andy