We need to start by finding out if this is a vacuum leak by running through this guide:
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
If you have a leak, clearly this will help identify where it is, but I also attached a diagram that lays out the vacuum and emissions system.
We also need to check and see if this is a misfire. Just remove each spark plug wire one at a time and make sure the engine runs rougher than it is and that will show that this cylinder is starting to misfire.
If you remove a wire and it makes no difference, then this cylinder is misfiring, and it needs to be inspected further.
https://www.2carpros.com/articles/engine-misfires-or-runs-rough
Please see below for more info on this and let us know what you find with this.
Thanks
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Tuesday, October 19th, 2021 AT 6:27 PM