I have a 2002 Nissan Maxima with Automatic transmission that is shaking very hard at idle and in gear. I think it could be either motor or transmission mounts. My question is I have never replaced the timing belt and the car has 125K miles if the belt were failing would it shake as well or what would be it's symptons?

 

That engine is actually chain driven, there is no timing belt. Do you notice alot of engine movement when the car gets put into gear, like you can see it shifting violently back and forth when the gear is selected?

 

Do you have any engine codes? And you can look at the mounts to see if they are eaten/worn away.

 

Ignition coils my friend.

 

^^^____ my first thought just reading the thread title. However, it is always a good idea to check your mounts if you've not. Especially the auto mounts, they are crap.

 

Check spark plugs as well. They will definitely cause shaking because of a misfire.

 

Motor mounts, ignition coils, harmonic balancer. Check those thoroughly.

 

if it is a coil, the shaking wil be all the time and when you are driving you will notice a real bad acceleration and bad noises coming from the engine. You need to look at the engine mounts and tranny mount. I have replaced the mounts and now going for the tranny mount and trust me the shaking is there.....