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Help....Misfiring After Putting In Remanufactured 3.7L Engine

Old 06-28-2019, 10:31 PM
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Mercury83
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Default Help....Misfiring After Putting In Remanufactured 3.7L Engine

I recently swapped a high mileage 3.7l ford engine for a remanufactured 3.7l ford engine in my 2011 v6. It included new spark plugs. When I got the car back, the check engine light started to flash and read misfires on two cylinders. It only happened when I aggressively accelerated on the highway, leading a mechanic to suspect bad coil packs.



We then immediately replaced four of those coils including the ones connected with the cylinders mentioned in the code. For a day it was fine, then the check engine light came back on and the misfiring became more noticeable and consistent. When I had the code read, it said misfire in cylinder 3 (one of the replaced coils), and a random misfire. Before we replaced the coils it would blink until I pulled over and stopped and restarted the car, then it would disappear. After those replacements it stays on and the car bucks and is constantly misfiring. It canít reach high rpmís and it vibrates on idle JA: What year is your Spark? I have all new spark plugs and 4 new coils. Whatever the issue is Iím suspecting itís electrical/computer based. Iím badly in need of ideas because Iím not a mechanic and I canít afford to keep throwing money at this. Any ideas on what this could be?
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Old 06-29-2019, 08:28 PM
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Sounds like maybe you need to reset your crank sensor.
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Old 06-30-2019, 01:44 PM
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Did you do the crank relearn procedure? Your description sounds more like that is the issue. If you ever separate the engine and transmission on a 2011+ you have to teach the computer where everything is again. If you don't do the crank relearn, then you will get misfires exactly the way you described.
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Old 07-01-2019, 08:42 PM
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Originally Posted by JimC View Post
Did you do the crank relearn procedure? Your description sounds more like that is the issue. If you ever separate the engine and transmission on a 2011+ you have to teach the computer where everything is again. If you don't do the crank relearn, then you will get misfires exactly the way you described.
Sorry about the multiple posts, I just donít have a huge budget to figure this out and am freaked out. They recalibrated the crankshaft sensor today and cylinder 3 is still misfiring very noticeably. I just donít know what else it could be.
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Old 07-01-2019, 09:12 PM
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It isn't the crankshaft sensor. There is a procedure you have to follow that is the crankshaft relearn. If you have a SCT X4 or newer you can do it yourself. Since you are still getting the misfire it sounds like your installer has not done the proper step.

If it isn't done you can damage the engine. I had to replace an engine and ended up with massive oil blow by (had put a turbo on it so was tuned). Ended up with a hole in a piston. That installer put the next engine in and I was getting the same symptoms as you (had removed the turbo and gone back to stock). When I asked him if he had done the crank relearn the response was, "uhhh, I'm sure it was done if it is required". Stopped by the dealer and asked them to check and the relearn had to be done. No problems on that engine after that; probably caught the problem in time and the fact that I had put it back to stock.
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Old 07-02-2019, 10:26 AM
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Originally Posted by JimC View Post
It isn't the crankshaft sensor. There is a procedure you have to follow that is the crankshaft relearn. If you have a SCT X4 or newer you can do it yourself. Since you are still getting the misfire it sounds like your installer has not done the proper step.

If it isn't done you can damage the engine. I had to replace an engine and ended up with massive oil blow by (had put a turbo on it so was tuned). Ended up with a hole in a piston. That installer put the next engine in and I was getting the same symptoms as you (had removed the turbo and gone back to stock). When I asked him if he had done the crank relearn the response was, "uhhh, I'm sure it was done if it is required". Stopped by the dealer and asked them to check and the relearn had to be done. No problems on that engine after that; probably caught the problem in time and the fact that I had put it back to stock.
So what is the difference between recalibrating the crankshaft sensor and a crankshaft relearn? The dealership says they did the former.
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Old 07-02-2019, 10:32 AM
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Iím also concerned because at first like I said the check engine light would only flash at high rpms and I couldnít really feel anything wrong until that happened. After replacing the coils, now the car is misfiring noticeably, bucking and shaking and the code still firmly reads cylinder 3. This seems different than what was happening before.
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Old 07-02-2019, 05:42 PM
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The dealership MIGHT be saying the same thing in different words. However, since you are still having problems and they are worse than before, I don't think that what they did was the crank relearn. The is different from adjusting or recalibrating a sensor. It is a programming of the computer so it knows where the crank is at all times and can then handle the timing and other things. If all they did was adjust a sensor then that could be what is causing your issues now.
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