Ignition-system glitch will likely require a pro
Question: I have a 2007 Ford F-150 4x4 with a 5.4-litre threevalve Triton engine and about 135,000 kilometres. The truck runs well, with one exception.
If, when cruising above 70 km/h 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 0-70 km/h. 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 is in overdrive? I’ve checked around, and some possible solutions are replacing the plugs or the coilon-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.
M.A. Answer: 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 brokenoff 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 brokenplug 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.
Q: I leave my 2010 Subaru Forester in my New England garage for three months and have a friend start it up, roll it out of the garage for 10 to 15 minutes once a month while I am away.
You recently mentioned a battery maintainer. Can you explain? My friend found the battery dead this past week after two months in the garage.
K.S. A: A battery maintainer is simply a battery charger, or trickle charger, that turns itself off when the battery is fully charged and then back on as needed. Continually charging the battery after it reaches full will damage it. A battery maintainer will switch itself to a “float” mode and keep the battery from both over- and undercharging.
Q: Recently, my wife’s 2003 Toyota Highlander turned 240,000 kilometres. No sooner had it done that when the timing belt snapped and, in so doing, damaged and froze three pulleys and knocked out the water pump. Our longtime service person repaired the damage and said it could have been worse had the car not had a “noninterference engine.” The internal engine parts were not damaged despite the severity of the occurrence. He further indicated that if our vehicle had an “interference engine,” he’d be telling us that the engine was totalled because such damage to an interference engine would wreak havoc on the inside of the engine as well.
Since the repair, the Highlander runs perfectly. Can you please explain more about interference versus noninterference engines, and how one can tell which kind of engine is installed when purchasing a vehicle?
P.M. A: A noninterference (freerunning) engine will not be damaged if the timing belt breaks. Despite the valves being out of sync with the pistons, these components will not collide with one another. There is adequate space between them, even when the pistons reach top dead centre. Interference engines, on the other hand, have little space, so if the belt breaks, valves and pistons crash into one another, bending the valves and damaging the pistons. Fixing the damage is expensive. The simplest pre-purchase tack is to ask the service manager.
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, California. Readers can send him email at bradbergholdt@gmail.com.