I'm experiencing pretty aggressive engine vibration at highway speeds, usually 45+. It causes the ride to be very rough. 98K miles and just replaced spark plugs and the throttle body has been fully cleaned. When I take my foot off the gas, the vibration disappears. Has anyone had this issue? Want to find out before taking it into the dealer. Thanks!

 

Year and Model? No CEL?

When you say "just replaced the spark plugs", do you mean like right before this problem started?

What kind of spark plugs did you use for replacements? Did you drop one before the install?

You need to determine if you have a driveline problem or if your engine has a miss. Although it is super easy to do an I5 plug change, you would be surprised how many times people mess it up.

The plug needs to be installed, then the coil boot needs to be put on top of it STRAIGHT and fully seated/snapped in place, BEFORE the coil pack bolt can be tightened. If any one of those coil packs was not put on correctly, you will get some kind of miss.

 

It's a 2006 H3, not sure what a CEL is. This problem occurred before the new spark plugs instal so this is nothing new. The plugs are ACDelco iridium and none were dropped everything was installed properly and there is no engine light or message. It probably is a driveline issue.

 

CEL = Check Engine Light

I would look at shafts and U Joints, even wheel bearings.

Good luck.