Q: I have a 2007 Ford F-150 4x4 with a 5.4-liter three-valve Triton engine and about 84,000 miles. The truck runs well with one exception.
If, when cruising above 40 mph with the transmission in overdrive, I gently accelerate, the ride can become rough (like on a bumpy road) or sometimes what I'd describe as herky jerky _ a rapid forward-and-back motion. The symptom stops as soon as you let off the accelerator or accelerate hard to kick it out of overdrive. It idles fine, and acceleration is smooth from 0-40 mph. I checked the vehicle with a diagnostic scanner, but that returned no trouble codes.
If the ignition or fuel system is causing the problem, why does it only occur when the truck's in overdrive? I've checked around, and some possible solutions are replacing the plugs or the coil-on-plug ignition coils. I'd rather first identify the cause than just start replacing parts in hopes of solving the problem. Also, if you can recommend any spark plug removal tools that work well on this engine, I would appreciate that as well.
_ Mitchel
A: It sounds like you may have an ignition system fault brewing.
You're most likely to see such an issue rear its head when cruising with a slight-to-moderate load, not unlike the driving conditions you described. The problem will lead to intermittent misfires. Your "herky jerky" comment is the best-ever description of this symptom.
Your truck's misfire seems to be brief or intermittent enough that the on-board diagnostics system has not yet identified it as a cause of excessive emissions and set a trouble code. If your scan tool displays Mode 6 information, you may be able to see which of your eight cylinders is the culprit by viewing misfire history.
The most likely causes of ignition misfire are, as you mentioned, faulty spark plugs or coil packs. If you know which cylinder is misfiring, swapping that coil to a different cylinder, going for a drive, then rechecking misfire history could nail the cause. (If the other cylinder now shows misfiring, the coil is the culprit.) Coils can also be tested by removing them, one at a time, and plugging them onto an OTC 6589 or similar spark tester connected to engine metal. Wrapping the coil with foil (also touching metal) encourages spark leakage, the most likely fault. If all eight foiled-coils spark the tester as the engine is cranked or briefly run, they are good.
This leaves the spark plugs. Ford truck Triton engines built between 2004-2008 (also certain Mustangs, Explorers and motorhomes of similar vintage) are susceptible to spark plug breakage upon removal due to an unusual extended tip that seizes in its bore. The upper part of the plug comes out, but the broken-off bottom half remains.
There are numerous tricks and recommendations to mitigate this, such as running Sea Foam cleaner in the fuel during the preceding two weeks, which loosens combustion chamber carbon. Next, you'll soak the spark plug wells with carburetor cleaner, loosening the plugs just an eighth or a quarter of a turn, soaking again, perhaps overnight, and then again upon removal. Use an OTC 6918 spark plug removal tool (grabs the plug in such a way breakage is claimed to be less likely) and then finally a Lisle 65700 broken plug removal tool (appropriate for the three differing ways the plug may break).
There are countless professional articles and YouTube videos concerning this situation. Even so, I would recommend having the plugs removed and changed by someone with considerable related experience as there are several ways for this to go very wrong. After viewing Ford's technical service bulletin on the issue, I think you'll agree this isn't a job for a first timer. Newer plugs, installed with anti-seize compound and changed more frequently, should alleviate future concerns.
