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Rough Idle/Stumbling in General But Especially After Fill-Up

24K views 31 replies 12 participants last post by  2019_FFS  
Nice - looks like a 1 beer job.
I know it's hard to quantify, but how much 'shake' does your car have with the solid mounts? Still family friendly?
I usually end up putting Poly motor/trans in my cars, and love how stiff they are for a few weeks. Then they start feeling 'soft', and I regret not doing solid...
I guess it depends on your family, but mine complains about it constantly. I’d say the motor mount was not a problem but the trans mount transmits a lot of vibration and noise into the cabin.
I guess the fact that early reviews and customer feedback on the FuSport featured complaints that the transmission shifted too harshly in Sport mode (!?!) is an indication that the average passenger is not going to like the feeling of mechanical connection that we prefer.
 
I changed mine 10 days ago and I’ve filled up twice since with no choking & stumbling as before. Idle is still a bit…crunchy. But I believe it’s definitely a tune thing that’s being exacerbated by the solid trans and motor mounts.
 
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I’ve always had a rough idle since day one. Mild at first, then it got worse as I did more mods. After switching from LMS to SCT this spring, it improved a bit. That said, I’ve also had the Wynn fuel system flush and valve cleaning done twice resulting in very mild and temporary improvement in idle quality, improvement in throttle response, and notable improvement in fuel economy. Others experience may vary especially since my car is so far from stock and fuel quality in this part of Ohio and my territory in the Allegheny Mountains just sucks out loud.
 
Very rough. I’ve had mine nearly stall out.

I’ve never had it last more than a couple minutes because I usually fill up then drive a significant distance before stopping.
It happens when I fill up by leaving the pump handle locked and allowing it to automatically shut off when it’s full. It’s not “topping-off” in the sense of feathering the pump handle to fill beyond the auto shut-off, just a normal fill up. I always fill my tank fully (except on a race day where I might keep it to 1/4 full) because I’ll typically drive out an entire tank in one trip. Often, I’m going somewhere that my schedule, the distances, and available fuel stops are such that filling up is the best way to manage my time.
 
Ford parts catalog didn't even show this as a purge valve when I looked at it. It was labeled as something like fuel support bracket. But it's the purge valve. Just looks different from other Fords/EcoBoost applications.
And they say it does not fit my car.
 
Been having this problem since 80k. Thanks for the fix!