First of it looks like you guys have a great forum here and some really good information. I have a 04 SR5 V6 and I changed the plugs last night. I was very careful and thought I did everything correct. Took the cover off of each one and removed them one at a time. Vehicle starts up and runs just fine but when I'm at a stop light I can feel a knock. It's very random and does not make a noise or do anything with the RPM's. It is just something I can feel when idling, sometimes it is every 2-3 seconds, sometimes it is every 5-10 seconds. It almost feels like there is a plug missing or something like that but the performance and ride seems to be better than before. Any thoughts or suggestions on what this problem could be?
Thanks,

 

I would go through and make sure every plug boot is fully down on the plugs first--those suckers have a tendency to stick up high on the plugs. Maybe spray some silicone spray or similar electric lube inside them first. Hope you find it!