Bad Ignition Coil or Something Else?

[tjw7676]

First of all I would like to thank everyone here for this website. It has helped me to save a lot of money on my xc70. My Xc70 is a 2001 with 173K on it, new upper engine mount and lower transmission mount put in about 3K miles ago. I had new plugs and the vehicle has a new transmission that was put in at 158K before I purchased it (neutral stop deactivated also). I have been experiencing a shake during acceleration that is most pronounced between 15-30 mph, but I can feel it anytime I give her gas on the highway. Instead of a shaking the dash, at speed it represents itself as a vibration that seems to follow the engine firing. Here is my question; is it a bad ignition coil, or multiple ignition coils? I took off each coil and then applied dielectric grease to each connector and to the top of each plug; this lessened the severity of the shake and made is less pronounced. I also took each plug and inspected them; they were perfect. I don't think the ignition coils have been replaced for a long time; so I went ahead and order a new set of 5 just to be sure. Could it be a bad axle, cv joint, or bad coils? Sorry for the long thread, all help is appreciated! :)

[Blessyouboys]

If the plugs all look good, that would tend to discount an ignition problem.

Is there any noise associated with the vibration? Have you checked all the motor mounts?

[tjw7676]

I replaced the Top Crossbeam motor mount and the lower transmission mount very recently. I visually inspected the other mounts, and didn't see any severe wear from what I could see. I have driven with windows down trying to listen for popping or other sounds, but cannot hear anything when it shakes. When it first happened, it would shake the dash and wheel, and then I cleaned the coil packs with dielectric grease and that seamed to help with much less shaking. Thanks!

[Blessyouboys]

The absence of any noises makes me thing it isn't a CV joint.

The absence of any codes, and the condition of spark plugs as you have described makes me discount any ignition problems.

Have you tried rotating the tires to see what happens?

[tjw7676]

I will go ahead and try and rotate this weekend and see if that helps. I will post an update if that helps. Thanks.

[tjw7676]

Just as an update for everyone; I took the car the dealer since I could not figure out the problem. It appears that it is a front right drive axle that has gone bad! From what the service manager said, the front right goes out more often than the left. Parts is on its way and should be here Monday for them to install! Shake under acceleration = bad axle.