Ford Dealership Misdiagnosed a Coil and Plug and Gave a Ridiculous Estimate of $1,200 for a Misfiring Engine Problem –Here is the Correct Diagnosis and Fix That Rescued This Truck From the Dealership.

A 2010 Ford Explorer with a 4.6L 3-valve engine and just under 73,000 miles on it developed an intermittent cold start engine misfire. When brought into a Ford dealership to see what the problem was, the owner was given a diagnosis of needing a new coil and plug for cylinder #8 and an overpriced repair estimate of up to $1,200.

The owner declined the repair and decided to DIY the spark plug and coil, only to discover that the Ford dealership's diagnosis was wrong.

Related article: Why Ford Customers Don’t Trust Ford Dealerships to Fix Their Cars

The owner wisely decided it was time for a second opinion before spending any more money on a misdiagnosed repair and took his truck to a well-known Ford repair expert.

Related article: Fatal Flaw of This Ford Truck Engine Rescued from a Dealership Fail

Help from the Ford Tech Makuloco Channel

From the same Ford mechanic who brought you an informative fine point of a common and straightforward cause of engine misfires in Ford Explorers due to rainwater intrusion from the windshield wiper cowl drain port, here is another example of how the Ford Explorers wind up with an engine misfire using this Ford Explorer misdiagnosis story.

The Value of This Video

The value of this story and the following video is that they demonstrate how to diagnose a common engine misfire source in Ford engines. In the video, you will discover:

• One common cause that was not the case in this misfire incident
• The importance of a proper diagnosis before starting any repair
• Why you should always seek a 2nd opinion―especially when it involves expensive repairs.
• With some basic tools and a little knowledge, you may have in your garage and mental toolbox, respectively―and a little common diagnostic sense―a DIY mechanic can diagnose if not achieve a successful misfire engine repair that will save them a significant amount of money.

That said, the video is well worth watching. If you prefer, a summary of the video is provided below for your convenience as well.

Ford Explorer 4.6L 3v Mystery Misfire Only When Cold Fixed!

Ford Explorer Mystery Misfire Summary

Like a murder investigation, the host follows his investigative instincts and experience to determine whether the misfiring engine problem really does occur at cylinder #8. Then, he follows a systematic diagnostic pathway to determine what is going on that could explain the intermittent misfire.

Key points to the diagnostic path (in order) include:

1. Verifying with a scan test that points toward the problem as being isolated to cylinder #8.
2. A cylinder balance test confirms that cylinder #8 is misfiring, with the added information of how often and to what extent. In this case, it was only occasionally when the engine was cold and not indicative of a blown coil or toasted spark plug.
3. A perfunctory cylinder compression test with the scan tool ruled out one cause of engine misfires; all cylinders were fine compression-wise.
4. Noting that the coil the owner used in the repair is very likely a faked OEM part by noticing slight manufacturing detail differences between the customer's coil and one the host has known to be a genuine OEM coil, the host acknowledges it could be a problem source for the owner's repair attempts.
5. Substituting the fake coil with a known working OEM coil and finding that neither the coil nor the spark plug was the cause of the misfire problem.
6. The host proceeded to the next diagnostic test by removing the valve cover and inspecting the cylinder #8 valve roller follower, only to find it had worn down and was physically separated from the valve. This meant that the valve was incapable of opening fully, leading to poor air/fuel mixing, which manifested as a misfiring in cylinder #8. The Explorer owner was fortunate that major damage had not occurred just yet, but it was a likely possibility, given enough time for the broken follower to shift and break into smaller engine-damaging fragments.
7. The conclusion following the host's accurate diagnosis is that the original dealership garage missed the true cause of the problem by relying only on a simple scan code interpretation rather than an actual diagnosis. Not only would the misdiagnosis cost the owner needless expense by firing the parts cannon at the problem, but it could also have led to much more extensive and expensive repairs afterward. The host will repair the Ford Explorer by replacing the camshaft due to its damaged valve lobe face and replacing all valve rollers with replacement ones that do not fail as readily as the originals.

For additional Ford-related repair articles, here are three informative ones you should know about as well:

• Ford Engineers Have Lost Their Minds, Says This Mechanic
• Easy Ford Explorer Electrical Problem Fix That Will Save You Thousands
• How to Ruin a Ford 5.4L 3v Triton Engine with a Timing Job

Timothy Boyer is an automotive reporter based in Cincinnati who currently researches and works on restoring older vehicles with engine modifications for improved performance. He also reports on modern cars (including EVs) with a focus on DIY mechanics, buying and using tools, and other related topical automotive repair news. Follow Tim on Twitter at @TimBoyerWritesas well as on Facebook and his automotive blog "Zen and the Art of DIY Car Repair" for useful daily news and topics related to new and used cars and trucks.

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