Hey all. I am pretty damn good at diagnosing car issues with my butt "insert Niki Lauda joke" but the weirdest thing happened yesterday.

So I was driving along doing to a stop and all of a sudden I got massive vibration. The only thing I could compare it to was subwoofers producing bass for about 5 seconds, and then it went away.

I literally thought it was just somebody else's car blasting music with crazy subs.

Then, last night I went for a little drive. Stopped at a red light, and when the light turned green I went to turn right and it did it again! Same thing, about 5 seconds of heavy quick vibration.

First thing I thought was my differential, but I haven't had any issues with it so far, and it's been on the car for less than a year (Quaife built by Z1)

Other thing I thought it could possibly be is a seized or frozen caliper. But last weekend I changed the wheels on my car (balanced correctly and torqued correctly) and checked all 4 brakes and they all looked fine.

I am at a loss for what it could possibly be, and a bit frustrating as I have been considering moving on from the Z and recently decided to keep it another year and just ordered test pipes since my cat shields are rotted. Hoping this car doesn't turn into a money pit. It has been great to me for the last 8 years.

Any help would be appreciated.

 

possible that the abs unit going bad?

 

Trav, just want to first say that you are so helpful lol

How on Earth do I check that out?

 

i wouldnt even know how to check, a guy local to me had his go bad... but it would lock up his wheels so i am not sure. did it only do it when turning?

 

Since the only thing you did was change the wheels out, I'd check those first. The obvious things like pressure and lug torque. (I know, it sounds like I'm making you out to be a newb but seriously, if that's the only thing you did, ya never know. Ask me how I know that.... )

Only other thing I can think of offhand is clutch/flywheel. Did it do it while there was some type of clutch action going on (coming to stop/disengage, accelerating from stop/engagement... or more likely... somewhere in between engage-disengage with minimal loading, causing flywheel to chatter)?

Good luck!

 

So far it did it twice. Once was coming to a stop going straight, and the second was slow acceleration and turning

I know what you mean. I can assure that lugs are torqued properly, tires have correct psi and were mounted properly.

Both times it happened, the car wasn't jerking or anything. I had a diff blow on me before, and it was a loud bang and locking of the wheels. This literally felt almost like running over the warning strips on the side of a road, but more of a feeling like bass.

I know diagnosing over the internet is very difficult. I am just trying my best to explain what happened. I consider myself mechanically inclined and I am totally stumped by this.

 

Could be you lost some wheel weights. If they stuck them on a dirty wheel or it was a crappy adhesive, then one or more of them could have flown off at some point and caused a balance issue (would have to be pretty bad to get that kind of wobble though).

Also, if a weight flew off while your tires were spinning, it could have caused damage to something in that area. While you're under the car, check for anything that looks ripped or bent on all four corners.

 

Another thought... did you just do a visual inspection on the brakes, or did you check for warped rotors with a run-out gauge and reseat the calipers? Unless some foreign object lodged itself between your wheel and the rotor, or you torqued the lug nuts down wrong (which you said you didn't,) it's unlikely that changing out your tires caused brake issues. Until you do a proper inspection though (beyond visual,) you'll never know.

 

If it was a constant thing then I would think possibly a wheel weight or a wheel bearing.

It happened only twice in about 20 miles of driving. Every other time the car was fine, including this morning driving to work.

I just did a visual inspection to check the pad wear and the rotors to make sure it had no cracks. The front brakes have under a year on them (Akebono BBK) and the rear have pads with under 5k miles on them. Rotors looked fine to me.

Since the car drives fine now and it just happened to me twice, it leads me to believe that something is on its way out, not something that already broke.

Like I said, besides those two instances, the car drives perfect. No noise, no vibration, etc.

 

So I did some driving this weekend to try to pinpoint the issue and confirmed it's my brakes.

It happens most when I am slowly rolling around 1-2mph and slightly on the brakes. As soon as I release the brakes the vibration stops. It is almost like one of the pads is vibrating in the caliper as it drags against the rotor.

Very weird, never experienced anything like this on any of my cars.

 

If it's happening on a light application of the brakes at slow speed, it could be a dry or intermittently seizing caliper pin. Doing simple things first, you could just start by lubing the pins with some silicone grease.

 

Good call! When I install my test pipes next weekend I will lube the pins on my rear calipers. I highly doubt it's my fronts. The Akebonos only have about 10k miles on them.

Thanks for your help!