Infiniti I30t vibration problem

[MR.I]

Hello my 1998 Infiniti I30t vibrates when in drive and I'm stopped at a light. The steering wheel vibrates. I changed the spark plugs last year. The vibration stops when I have the heat or air on, or when it's in park. By the way, I haven't loss any power. What do you guys think the cause is? Thanks

[maxhopper]

It's really impossible to say with the information provided. I'd begin by looking for anything contacting the steering rack.

Is the check engine light on? Are there any codes stored in the ECM?

[loystock]

Based on your description, the problem is most likely with the engine mount(s). You can verify that with an assitant who will observe the engine while you rev it (2K or less), with Parking Brake ON and brake pedal depressed all the way while in Drive. If the engine seems to lift or rock side-to-side, then it's the engine mount(s).