cold start vibration after a new short block !!

[Eng_Ahmad1986]

greetings to all 🙂 

mine is 2019 mk8 fiesta 1.0 ecoboost 100ps automatic , current mileage is 17.6k miles. 600 miles ago I had my short block replaced at the dealer due to a white smoke issue, turned out to be the piston rings of cylinder no.1 was not installed correctly from factory !!

since the new short block installed I had this strange issue, I know our ecoboosts do vibrate when you start it from cold due to the open loop operation until the O2 sensor heats up and come into operation, it did so since day 1 , but this time the vibration during a cold start and warming up is excessive, excessive to the point that if the gear selector is at N and the parking brake is not engaged the car can move back and forth !! random hard engine vibration that shakes the whole car, the RPM is steady though.

been to the dealer several times, they replaced the transmission mount, they checked for any registered trouble codes, they performed a misfire test using the misfire monitor application, all was ok !!

last time they checked spark plugs gaps, they fount it to be 0.6 mm , the engineer told me that according to this engine specs the spark plug gap should be 0.7 mm + or - 0.1 , so it should be ok from 0.6 mm to 0.8 mm, however, they adjusted the gap at 0.7 mm , he told me to test again and if the issue still there bring the car again, I checked yesterday it was just the same !! I checked today morning it was there but not as hard !! wondering what this could be ?!! I have heard that after you disconnect the battery the engine takes time to relearn again its fuel trim and idle , could this be the issue ? or could the spark plug gap be the issue ? will it improve by time ?!! or there is another underlying issue that the dealer couldn't discover yet ?!! my biggest fear is that there might be an issue that affects the new freshly installed short block and I might go through this whole headache again !!

any one gone through this before ? or experienced any thing similar ?!!

note that oil and coolant level are ok , no lights , no trouble codes, and tests made by the dealer gave no errors !!

thank you very much and sorry for the long story 🙂 

[Eng_Ahmad1986]

it should be noted that these engine vibrations are not accompanied by any RPM fluctuations, RPM is stable all the way 🙂 

thank you 🙂 

[Jeipii]

Some vibration with revs 800-1800 is normal. Maybe they should check your engine mounts ? Those are the ones that transmit the engine vibrations to the car chassis.

[Eng_Ahmad1986]

On 9/20/2020 at 12:44 PM, Jeipii said:

Some vibration with revs 800-1800 is normal. Maybe they should check your engine mounts ? Those are the ones that transmit the engine vibrations to the car chassis.

they told me at the dealer today that they found nothing wrong with the engine mounts, and they are going to check valve clearance !!! 

I don't know what could have gone wrong with the valve clearance in a car that is one year old and 17k miles !!

[Eng_Ahmad1986]

update : turned out to be incorrect valve timing due to human error when assembling the new short block, they readjusted the timing, the car idles now very smooth whatever cold or hot 😄 

[tomshepp]

Little else it could have been. A good mechanic would have thought of that, known what he was looking for and wouldn't have been surprised to find it. Glad it worked out well.