Misfire/ rough idle

I got my engine swapped out and it ran smooth for about a month before starting to shimmy. It's been shaking like that for a year and I've kinda ignored it. It's gotten a little bit worse but not too bad but I'm starting to worry I'm low on compression in a cylinder maybe. It cranks up fast and the rotation is even with no gallop and no power loss either. It gets like 19-20 on the highway and feels fine. It's the worst when it's in neutral at 900ish rpms. In drive it runs way smoother but still has a little shimmy but it's negligible. Has anyone had a similar issue? I'm praying that it's spark plugs or coils but who knows.

 

And it doesn't shake the whole car or anything. You can only really feel it with your knee up to the door. Is there any symptom that I should look for that would indicate that it's sparkplugs/ coils? I'm procrastinating doing a compression test bc I don't wanna have to rebuild another f*cking engine haha

 

And by "shaking" I mean it runs smooth for 3 seconds - shimmys- runs smooth ect ect. The only time when it's a constant shake is when it's at 900rpm in neutral

 

Any codes thrown?

 

It takes like 30 minutes and $40 to swap spark plugs. Add on another 30 minutes for a compression test. I'd start there and see what you find.

 

Ever replace your engine and transmission mounts?

I had this barely noticeable gallop at idle in my truck. I tried plugs, plug wires, coil packs, all new vacuum lines. Nothing worked.

Replaced motor mounts and transmission mounts and the gallop went away.

 

OP what engine u have?

 

I think this is just the v6 doing its thing. Being a v6 it's naturally unbalanced and Toyota never used a balance shaft so it's naturally kinda shaky. Old motor mounts just hide this less.

 

One way to troubleshoot front engine mounts is come to a stop at a decline and see if it's shaking more. The extra weight tipped to the front amplifies it.