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Automotive/2000 Ford Expedition bogging down

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Expert: - 8/18/2007


Question
Hello-  I have an expedition that all of the sudden has begun to bogg and hesitate while I'm driving it.  It has always been the smoothest ride so it is very easy to detect when it is occurring.  Seems worse when AC is on, but even happens when off.  Starts fine and runs well when stopped, but will still occasionally feel hesitation.  You can feel it thru the gas pedal as you are giving gas and it jumps a bit and then resumes driving.  I should take it immediately into Ford, but warranty is over and I'm afraid of the price tag, but I am also concerned that this will get worse and I will have a major problem on my hands.
 Any ideas?

Thanks
Jeff

Answer
Inasmuch as your Expedition is a late-model PCM- or ECU-controlled vehicle, I would think that the very best idea would be to interrogate the module for trouble codes.  In general, problems of this type do get worse as the failure progresses.  If you are concerned about price - your concern being that you may find yourself paying for more work than might really be needed, you should make it a point to get more than one quotation, and seek references from any auto parts suppliers or fleet operators you know for a shop that is known to be reliable.

There is one possibility that you might check out yourself first:  How are the spark plugs, distributor cap and rotor?  Too, it might not be a bad idea to check the ignition harness.

Plugs do burn back over time.  As it happens, ECU/PCM controls do an admirable job of compensating for aged plugs until little is left of the electrodes and, at that point, the running becomes quite rough, especially when power is demanded.  The contact surfaces on caps and rotors also burn in time.

Ignition harnesses also fail, in terms of both their conductance and their insulation resistance.  As the resistive or inductive conductor fails, internal arcing will occur within the leads, robbing power from the plugs.  Again, this will be most notable when power is demanded.  Similarly, as the insulation fails, energy may arc through the jacket to nearby metalwork, shunting out the signal and again robbing the plugs of power.

None of these are very expensive to change, and should be done on a scheduled basis as a good preventative maintenance practice anyway, and so is a good idea even if none of these turn out to be the cause of this specific problem.  If nothing else, your repair bill for a more serious problem will be less by the cost of replacing these which probably be done anyway.

Check out the plugs, rotor, cap and harness, and change them if you have any doubts.  The Haynes guides give pretty good colour images of what good plugs should look like, along with images of plugs affected by a number of regular engine problems; in the case of your vehicle, the most likely plug problem would be excessive burn-back caused only by high mileage for the plugs.

Good luck ... EGK

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Ernest (Ernie) Kenward

Expertise

The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!

Experience

A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping. Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD. My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it. The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!

Organizations
IEEE - senior member ... past WCC Student Activities; SME - senior member ... past chair, greater Vancouver chapter chair 318; Edsel Owners' Club - have served in various capacities on chapter executive during seventies; have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.

Education/Credentials
Graduate of UBC

Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities

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