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Pinging, rough idle, cylinder 3 misfire

174 Views 2 Replies 2 Participants Last post by  cpc
My 2017 Ecoboost started having the following issues at around 65K miles:

1. Loud engine ping during acceleration first thing in the morning, but would stop pinging after engine warmed up for 5 minutes.
2. After engine warmed up, experienced very rough idle and sputtering to the point where it felt like the engine was about to shut off (but never did).
3. Engine trouble code reported cylinder 3 was misfiring. (Mechanic never told me what the actual trouble code # was).

Since I purchased a CPO vehicle, the powertrain warranty was good for 100K miles thank goodness. After several weeks of trial and error at the dealership, they replaced the cylinder 3 fuel injector, spark plug, coil and then the cylinder head, but none of these actions resolved the problem. ECU still kept reporting misfire on cylinder 3 but the dealer still could not determine why. Compression checks were always in the normal range.

Finally the mechanic kind of threw up his arms and recommended an engine replacement, or more specifically, a short block job. While they were replacing the engine block, they torn down the old engine and discovered cylinder 3 had scored walls due to a piston ring failure. So naturally, the short block replacement resolved the problem.

In conclusion, I just wanted to mention that during the lengthy trouble shooting/trial and error parts replacement at the dealership (which went on for about 2 months), the Ford Warranty office fought the local dealership tooth and nail to cover the costs and took several weeks of back and forth between them with slow response times and perpetual requests for many photos at different angles and close ups of various engine parts before the office finally agreed to cover the costs. The Ford Warranty office seemed to act like a reluctant 3rd party although the dealership assured me they were indeed part of Ford Motor Company. But in the end, I only had to pay a $100 deductible on two separate occasions during the months of aggravation. So I'm happy with my Mustang again.
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Warranty work can definitely have hurdles, but appears at the end you have a fix. I'm amazed the dealership didn't do a leak down test and not just a compression test. The leak down test would have shown that cylinder had a mechanical issue.
Yeah, the dealer's basic course of action seemed to be to "keep throwing parts at it" until the problem was resolved.
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