DigitalSynthesis

So, I've searched around and seen a few suggestions but no feedback on what fixed similar problems to mine. Here are the symptoms:

- BAD vibration under DECEL and ONLY between 70 and 50 mph.
- Does not matter what gear I'm in
- Does not matter if clutch is in or out
- Does not matter if I'm on the brakes or not, as soon as I go to light throttle it starts coming on, and gets progressively worse as I get off the throttle until it's nearly unbearable.
- Does NOT happen under accel, or steady cruise throttle.

Facts:

- Car has excessive negative camber in rear, I am working to correct this, but this problem has not always been here, and the excessive neg. camber has. I don't know if the camber caused the problem over time or what.
- Car is lowered. Toe seems ok all around.
- Car has ~2yr old energy suspension bushings and motor/tranny/diff competition mounts.
- Front camber is slightly positive. Yes, its wack. But again, that's been, and the problem is new.

Other info:

- Problem seems to have started around the time I developed a severe air leak in the right rear tire, but does not go away when the tire is properly full of air. I'm getting a full set of all 4 tires tomorrow and plan to check all suspension, bushings, bearings, etc. at the same time.

I'm scared that this is a phantom symptom leading to a hellish scenario of "buy this, fix that and problem does not go away" so I'm hoping that by being very specific you suspension experts can give me some targeted suggestions and eliminate options that are highly unlikely to fix the problem.

I HAVE tossed the car sideways over a curb, but the problem did NOT suddenly start after that event, nor did that event seem to affect the car in any way that I can point to. I'm including that for ancillary data. This problem started probably 2-3 months after that event. There was no noticable damage sustained in the jumping of the curb and the tire that has air loss is on the opposite side of the car from the side that jumped the curb, in case you were going to ask.

If you've got some useful info please help me out here. Its a daily driver and an only car so I can only really work on it on weekends.

RETed

TPS adjusted and in spec?
Slop in the drivetrain?


-Ted

Phantomkid

shot out of left field have you gone premix instead of the omp

DigitalSynthesis

I have a haltech, and the TPS is fine. I have gone premix. This occurs even with the engine disengaged however. Its a bad, bone-rattling vibration where the entire car bounces, as though you were going 70 with a flat tire. Which is why I thought it would go away when I have all the tires properly inflated. But it didn't.

As for slop in the drivetrain, well, I'll have to check further. None was obvious, for sure.

carbonblack

mine did the same thing, put on the ground control camber kit and it went away. best $85 I ever spent

DigitalSynthesis

Heh. That kit won't fit my shocks (Koni's). Sucks *****. Its sitting in a box in my room. And it didn't cost me $85, it cost me $250. Life's a bitch.

carbonblack

I was talking about the vertical camber link in the center of the car by the diff mount.

link

done right you can get about 2 degrees of correction just with this.

Mine vibrated when weight came off the *** end durring braking or off throtle (not as bad) now I have no camber issues and no vibration

DigitalSynthesis

Ahhh.... I have the mazdatrix one. Its already on the car, been on the car. I had it adjusted entirely the wrong way for a year and a half. I fixed it now, but it was bad before the vibration started, so unless it was an "over time" thing, that wasn't the direct cause.

Now, I've just crawled out from 2 hours spent under the car. Here's what I've found and done so far:

- Right front tie rod was LOOOOSE. Really loose. As in, rattling loose. I am pretty sure this was a contributor to my problem. I have realigned the front of the car, it looks pretty damn good now.
- Fixed the rear camber issue by both readjusting the Mazdatrix camber adjuster and by raising the coilovers by about 3/4" all around the car. Everything looks much more sane now.
- Inspected the driveshaft and rear drivetrain. Looks/feels/sounds fine.
- Ran the engine with the car on jackstands all the way around. Put it up to 5th gear @3k. No vibration in drivetrain when letting off the throttle, everything was smooth as butter, as they say. Also applied rear brakes via handbrake when on throttle. No vibration from that either. I'm 95% sure the drivetrain has nothing to do with it, but there's always the niggling "you missed something".

I'm fixing a few issues with the interior of the car and when the ground dries out after the torrential rain we just had, I'll take it for a test drive and let you guys know what's up.

Also, I checked for blown shocks, no evidence found and all 4 corners are solid as usual.

DigitalSynthesis

Ok. Yet more info.

Test drove car after above work. Fine up until 3rd gear then AWFUL pounding, bumping, etc. Took car back home, jacked it up again. Found out I'd shoved the adjustable part of the rear subframe against the body in my overzealousness to fix the camber issue. Readjusted camber so subframe is not touching. Ran car up again on jackstands, and WHOA. Vibration is there without car on the ground!

Ok, might be tires, right? Took rear tires off, ran just the drivetrain up to 4k in 5th. Bad vibration between 3 and 4k. Not looking good (for homestar runner). So, I'm thinking driveshaft is FUBAR. Go underneath one more time just to make sure I didn't miss something.

WHADDYA KNOW. There is a nut missing on the right axle. AND an entire bolt missing off the driveshaft connection to the differential!! And two of the other three bolts are loose!

So I got really cautious, replaced the missing fasteners (fortunately I have about 3 cars worth of bolts laying around), re- (and slightly over-) torqued everything I could find down there. Ran it back up on the stands, much much better. So I'm *HOPING* that fixed the problem. I'm going to go out and grab a bite to eat and when I get back I'll let you guys know what's up.

I can't believe so much was loose underneath. I'd torqued EVERYTHING to spec, used the appropriate locking devices (lock washers, etc), most of the fasteners I used were new, and after I'd driven a few hundred miles I'd retorqued everything. I've got no idea why stuff was like that. Who knows. Guess I should start using locktite on everything.

DigitalSynthesis

All right. I haven't done a highway test yet but I hit a superwindy road near my house and hit speeds at which I KNOW there was bad vibration before, and the entire ride was smooth as glass. I had no idea my car could EVER get that vibration free. It's been this bad nearly since day 1. I thought it was the harder bushings and everything.

So, until something else comes up, I think we're golden. I'm going to start saving my pennies for a new driveshaft though. I am pretty sure with how bad those vibrations were they radically shortened its current life.

Hopefully this will help someone else if they run into this problem.

RETed

I thought I said...



Uuuuuu...didn't know it was a Haltech.
Just another thing to look at...
How is your decel cut set at?
What is the rengage RPM?
Under 2,000RPM?


-Ted

DigitalSynthesis

Decel cut is set, and reengage is @ 2k rpm.

But everything is SMOOTH as butter now. Its wonderful!

And, yeah, everything "felt" tight when I went under the first time, apparently both bolts were rotated to the top where I didn't see them. Shame on me for not spinning everything by hand... who would have thought a missing bolt would cause so MUCH vibration??? Now I know. :-D

Yah, Ted sorry man I forgot we haven't talked in a while, kinda assumed you'd remember. ;-)