2010 Mercury Grand Marquis. We recently purchased it and the dealer said the tires might need balanced since it had been sitting for a while (over a year). Anytime we drove over 60 the front end started to vibrate. Took it to a tire place and due to dry rotting they recommended new tires. So, over $900 later, 4 new tires and a front end alignment we thought our problem was solved. After a quick drive on the highway, the vibration proved it was still there. Took it back to the tire shop: checked the front in, nothing needs replaced, brakes look good, three tires were good but the left front needed a small adjustment to the balance. Also adjusted the tire pressure since the TPMS light keeps coming on. However, it still vibrates above 60. Besides two different techs messing up the balancing, what else could it be? (and the TPMS light has returned as well).
Something is worn out. Check tie rod ends.
Yeah check for worn suspension parts like @doc mentioned.
However, since the shop couldn’t even balance brand new tyres correctly, the first time around, try swapping the front tyres to the back and check if the vibration goes away.
If it persists, I’d first find a reputed balancing & alignment shop and have them diagnose what’s really going on before you throw more money for another round of balancing & alignment.
Was this vehicle ever in a wreck, before? Any clues as to why was it sitting on the lot (for over a year) in this used car climate?
It sounds like the alignment was done by Ray Charles.
LOL by touch & feel only..