Nissan Repair: 1999 Nissan Quest, cv joints, nissan quest

Question
I had the engine replaced in Jan '06 after the timing belt went.Since then ,I've had 2 problems. The car has intermittently started to shake when going 50mph or more.The rotors and pads were recently replaced but the shaking  happened on the drive home.The tie rods , cv joints,boots have been done.There is noise when turning the wheel lft. or rgt. The power steering belt has needed tightening twice since the engine switch. The 2nd problem is rough idling and it doesn't feel like it's running smoothly.I just had the distributor,dist. cap,rotor ign.,fuel filter,air filter replaced.The codes were 0340 and p0325.I had hoped to keep this car ,but I've spent $3800.00 since Jan. and it's still not running well!! Please help!!  

Answer
Sandra,

The shaking is probably due to wheels being out of balance since you did have the rotors replaced.  If the shop did the work they would have noticed if the CV driveshafts needed replacement?  I would ask the question.  You have not seen grease on the front wheels have you?  If so the boots have torn and would have to be replaced.  The first code indicates a misfire and that could be the distributor itself or a coil.  The second code is the knock sensor.  Both of these codes are common on the Quest and should be taken care of.  After six years it is normal and worth the cash since you have done everything else.