Any auto mechanics out there?

This may seem like an odd request for a preparedness site but hey,  I am willing to give it a shot. My wife drives a 2007 Ford Expedition XLT. It is the 4×4 model. A few weeks ago the vehicle started running extremely rough. I know little about cars but I felt it was obvious it was not firing on all 8 cylinders. I had the check engine light check and it came back a couple cylinders were misfiring.

I suspected the spark plugs needed to be changed. I did a bit of research and discovered changing the spark plugs on this beast is a huge problem. The spark plugs are two piece models and due to a horrible design from Ford carbon builds up and locks the plugs into place. Performing a spark plug change often results in broken spark plugs. A local garage with a good reputation was contacted and I had them perform the spark plug change. Sure enough a couple broke and had to be extracted. Additionally one coil pack was replaced.

After all the work was done to the tune of close to $500 the truck ran very well with only a slightly rough idle. Two weeks it ran great and then started getting some hesitations. Between 40 and 50 mph there a definite hesitation and vibration that can be felt and heard. The hesitation is short lived as once I speed up to 50 it goes away. It seemed to get worse and worse and I could feel it misfiring periodically and the check engine light came on.

Another visit to the local AutoZone provided misfiring cylinders as the code. I decided to remove all the spark plugs and check them. They all looked good however I found one that was not tight in the well and I was able to unscrew it by hand. After checking all the plugs I ran the vehicle – no change.

A member of my preparedness group suggested I try resetting the vehicles computer. I disconnected the battery for about one hour. Upon reconnection and taking it for a test drive it seemed worse at first but then smoothed out. This step provided some success as it ran better but still has the hesitation and what seems like misfiring between 40 and 50 mph.

This is still how it is running. I can feel a “skip” every now and then while cruising however between 40-50 it is pronounced.

I have tried several Seafoam Gas Treatments and also tried the Seafoam engine treatment through a vacuum tube.

Again – I am far from being an auto mechanic but my next step is to change out all the coil packs. Oh – no check engine light anymore which I find odd as there is a problem.

The car is drivable it is just irritating and I would hate to have my wife be driving through downtown Charlotte, NC and have a spark plug explode out the hood into orbit.

Figured just maybe someone would have some advice.

So – any thoughts?


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  1. I’m not an ASE mechanic, so here’s my .25 cents-inflation, ya know 😉

    -for resetting the computer, unplug one of the sensors-MAP, TPMS, etc… start the engine, shut it off, plug in the sensor, clear the code and drive 60 to 80 miles to reset the computer.

    -when was the fuel filter changed? if it’s dirty, that will reduce the fuel flow and the engine will work harder.

    -are the wiring connections for the coil pack dirty or damaged? that would cause an interruption in the electrical current flow, which could mimic a bad spark plug symptom.

    -have you tried zmax? that’s as good as sea foam, and I’ve had good results using it in my truck. Try a bottle of that in the gas tank.

    Hope you get it resolved.

  2. Rourke,

    I am a certified mechanic. Since you had the spark plugs replaced already, the only other things that can be causing the misfires can be coils, or lack of compression. Although it sounds like bad coils to me. The misfire codes that you are getting indicate which coils are probably bad. P0301 would indicate a misfire on # 1 cylinder, P0304 Would indicate a misfire on cylinder #4 and so on. When spark plugs go bad they require the coil to work very hard to produce and send spark to the plug, this weakens the coil and causes failure. The engine that you have is a 5.4 Liter 3 valve. There is a coil for each cylinder, read the codes, replace those coils, all should be well.

    Resetting the computer cannot be done by unhooking sensors or driving 80 miles. The computer systems after 1995 are what is known as OBD2. There is only one way to turn the check engine light off, FIX THE PROBLEM, and have the codes cleared via handheld computer scanner.

    Should you have any questions feel free to e-mail me and I’ll hook you up with my phone # Tony

  3. I just reread your post and saw that you are not getting a check engine light. That’s because Ford systems have to misfire over 600,000 consecutive times to trigger the check engine light. If the misfire clears up even for two or three revolutions the count has to restart. It makes tracking down the offending cylinder a little harder. The professional scan tools are able to read misfire history from a generic database within the Ford computer system. Most store bought scanners however wont show this type of data. The other option is to start the engine, and one by one, unhook and reconnect each coil from the top wire harness at the coil and listen for a change in engine speed. If you have a consistent misfire and listen carefully you should be able to isolate the bad coil. Tony

  4. I’ve had the same problem twice now. Once on an ’03 Expedition and two months ago on an ’07 Expedition. The ’03 required new coils, new spark plugs (only one broke on removal) AND a new computer. The computer then had to be set at a FORD dealership as apparently it was super secret coding that only FORD and the NSA had.

    The ’07 was a bit easier (at $480) but the changed the plugs, and had a tune up (probably because I didn’t keep running it as long while it was skipping due to my paranoia from the ’03). I can’t remember if I had a bad coil this time or not, but I didn’t need a new computer or a re-programming.

    My suggestion, start with looking at the coil and if they are good, start saving for the new computer.

  5. I once had a similar problem with an old GEO Metro. I changed the O2 Sensor and it ran well for an other year. Then the trouble returned with vengeance and I isolated the trouble down to the throttle body positioning sensor. This part cost more than the car and so it was parted out.
    Good luck.

  6. I have a Chevy S10 with 396,000 actual miles on it. Same engine no rebuilds. Runs excellent I just go to the local u-pull salvage yard and get ignition parts from there. Ignition parts from parts stores are rediculously priced, course you already know that. Most of the guys that work there will give you the parts for next to nothing because hardly anyone buys them.Most vehicles in there are from accidents or trans failures. I even have spare distributor, brain box, all ignition parts in a faraday box, you know why. Just a few tips. Good Luck

  7. Hey there, I am an industrial mechanic and don’t work on cars other than my own, I have a ’99 ford pick up.
    You said, you replaced plugs and coil pack. Does the unit have plug wires? or does the coils sit on top of the plugs? I don’t know about your unit specifically as it’s built but I have experienced similar issues with wires breaking down under load. Best of Luck

    • Monty – Rather than spark plug wires it has coil packs sitting on top of the plug. One was found to be bad via code reader early on. From the research I have done it seems that it is not uncommon for them to be replaced frequently with age.

  8. Yeah wasn’t sure. Well the only other thing I can tell you is I have had cam position sensors act up and cause rough running. Most are easy to change but difficult to get to. Best of Luck.

  9. 1st question do you have a loss of compression on any cylinder? If there is no loss of compression, do you have a knocking noise(cam phasers) from the top end? If no noise, then I would suggest replacement of the coils and plugs with Ford parts. Aftermarket parts are fine for a short time, but they will fail very quickly. BTW I work at a ford dealer and see this all the time.

  10. Yep. wires and coils are a common cure for your diagnosis..and they are a pain to replace (especially if you happen to break a plug)…I’m not a mechanic but I do work in the parts dept at a Ford dealership and have a car that we drag race (I drive, my buddies are good mechanics that work cheap).

  11. Rourke, I’m not a mechanic but have just gotten done with one of those repairs that make ya wanna pull out your hair. After finding nothing wrong after replacing all the electronic parts from the distributor (not just cap n rotor but the whole thing) all the way to the plugs, the last option was an $800.00 computer. There is a company called Circuit board medics in NC (I think) that fixes auto computer boards at a fraction of the cost. I paid 200. I was a little leery as I’m not a big online shopper but took a shot. I mailed it in and had it back 4 days later and the car runs better than it has in years. What I saw on my computer board matched something I had read about quaternary salt diodes. Under one of the diodes was a small black spot consistent with a leaking diode… Glad I tried them and am a very happy customer. You can find em online and call and ask about your situation. Very helpful customer service.
    No I’m not affiliated with this company!! Hope ya get it figured out and thanks for all your hard work! Oh, I voted for ya!

  12. I am a mechanic and I have been my whole life. I would like for you to call me and I can give you some advice. My cell number is 520-870-6034. I think I may be able to help.

  13. I have a 1998 Expedition that has done/is currently doing something similar. On mine there is a rubber elbow part (PCV valve, maybe) at the rear of the engine compartment that, over time, develops a crack. This causes a change in vacuum pressure and causes my engine light to come on with a P0171/P0174 code. When the problem is BAD, my truck will shut off when stopped at intersections and it runs rough as HELL.

    See if this description sounds like your problem:

  14. tony is spot on iam a ase master tech and a smog tech.the first thing i recomend is to re ck the code it will be on soon if not now pointing you to the failing coil.Cam phasers are a slim poss but usually affects whole side of engine not just one cyl

  15. Hi Rourke,
    Take a hint from an Alaskan – we don’t trust anyone but ourselves!

    Tony is 100% correct so follow his advice.
    To rule out compression the compression possibility could easily be checked with a gauge.
    It is most likely the coils. Your mechanic could have checked for this and probably should have. Intermittent electrical problems are hard to find and most people just trust the computer even though it is set to ignore a bunch of misfires. I’d replace all of the coils and plugs.


  16. you guys suck 🙂 that engine has variable timing and a history of the variable timing cam malfunction. costs a couple hundred for the part but labor is steep as a whole lotta crap has to be moved to get to it. there are also two tappets on top that use a tiny orifice to sense oil flow, which has some mysterious thing to do w/ the variable timing. dif stories from engineers on what exactly they do, but they get clogged very easily and can mimic the vtc symptoms as well. i just switched oils and theory is old deposits clogged mine. saving up to fix it. have fun.

  17. Not looking to get into a pissing contest with anyone but, INTERMITTENT misfire felt when trans torque converter clutch is applied (40 – 50 MPH)is ignition system (plugs – coils). Vacuum leak would cause lean codes, VVT would affect one side of engine and also set a cam or vvt solenoid code. Rourke, change coils and don’t look back. I have done thousands (yes thousands) of them. Tony

  18. This may be opinionated, but I never had good luck with Fords – particularly their engine design. It seems their valve trains run way too hot. Beyond that when they have a good design they don’t stick with it. BTW A tow truck driver once told me FORD stands for Found On Road Dead.

  19. You can Google all this….

    Clean the Mass Airflow Sensor… MAF sensor specific cleaner.
    Clean the throttle body… TB specific cleaner
    Replace the fuel filter.
    Replace O2 sensors, as needed…See error codes.

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