Been a while, glad to say.

But here we go again, I turn to the real experts who've been through the dirt with these jks. My 09 wrangler has had an engine shudder at about 50 kms and 80 kms. Took it to the mechanic, and turns out according to him the spark plugs are 190kms old. And replacing them should fix the problem. (Coil pack was replaced maybe a few years ago, not plugs/wires)
I purchased the plugs and wires, installed them.
Now the engine still shakes , but at different kms/h. 40 kms and a slight shake around 70 kms. So new only changed the shuddering. The mechanic told me to try and ride the shaking until the computer recognizes it and throws a code up. But it only lasts maybe 2 seconds and sporadically reappears in and around those above mentioned speeds. I'm very capable under the hood , any leads would be appreciated at this point. I've read cleaning sensors, injectors and just need to properly diagnose the cause before throwing more money at her.

Side note, a year ago before ever seein a mechanic I dropped 2k on front end parts from u joints to even axle shaft and hubs. I mean I was a total idiot to assume the shake was drivetrain related and just went ham. And only a mechanics could have set me straight by telling me it's a 100 dollar fix. While it changed the shaking, it didn't fix it in full.

Any suggestions please. Thank you in advance. Cheers