Hey guys,
I stumbled into what seems like a decent deal on a series 5 89 RX-7 convertible. I have been playing tag through email with the seller,and looked at the car a couple of times over the past month. The seller lives in Boston, but the car is in the garage of his summer home on Martha's Vineyard, so it has been a little tough coordinating things. I finally got to hear it run today,and drove it for about 15 minutes. During the test drive the car vibrated pretty badly, at all speeds, and gears, and the vibration didn't go away with the trans in neutral, or clutch pedal depressed.
I know little about the 2nd gen cars, but do know that Miata's of this vintage suffer from vibration issues. The seller thinks it is more than likely from flat spots on the tires, and that may be the case, but I am unsure. The seller says that car has been sitting most of the summer, and he doubts he put more than 100 mile son it this season. Could it be flat spots? Could it be wheels out of balance? Could it be both? Could it be driveline related? Do the RX-7's suffer from vibration issues like the Miata?
Any help would be greatly appreciated. By the way the car has a few other issues like needing a new top, and some rust in a few spots, but it is actually fairly clean, and ran fine during the test drive. If nothing else the stereo is worth half the sale price, or was when it was new. It is hundreds less than challenge price, and I may just get it to enjoy for a short time, fix up, and sell in the spring.
Chris
Check the engine mounts too. AFAIK FCs don't generally have vibration problems, unless something is VERY wrong.
I have a set of 17" 5Zigen wheels on Dunlop Direzza tires that fit FCs. You can borrow them if you like to test the flat spot theory, you'll just need to drop by to get them.
RexSeven wrote:
Check the engine mounts too. AFAIK FCs don't generally have vibration problems, unless something is VERY wrong.
Driveshaft or CV Shafts could be the culprit. Relatively cheap fixes on an FC.
Dropped rotor/spun engine bearing + bad engine mounts would also do it.
Although, it would sound like a diesel engine at idle as well.
McTinkerson wrote:
RexSeven wrote:
Check the engine mounts too. AFAIK FCs don't generally have vibration problems, unless something is VERY wrong.
Driveshaft or CV Shafts could be the culprit. Relatively cheap fixes on an FC.
Dropped rotor/spun engine bearing + bad engine mounts would also do it.
Although, it would sound like a diesel engine at idle as well.
Didn't know that. Anyways, I have a couple of those too for an N/A car, which I don't need for my turbo.
I dunno. Maybe if the tires were badly under-inflated for most of the time they were sitting. I got my Turbo II inspected today and noticed that I have driven it almost exactly 250 miles this year, so mostly it sits. The tires are getting a bit old, but they don't have any noticeable flat spots and the car is nice and smooth and still pulls like a freight train on 18 psi.
Not familiar with vibration issues on FC's. 'Verts are pretty stiff, Mazda properly engineered the shell rather than just whacking the roof off a coupe and crossing their fingers (I'm looking at YOU, Ford, with the Fox Mustang) so that's pretty well ruled out.
Vibration in the steering wheel and seats (feel it in your butt) at all speeds including stopped at idle means bad engine mounts to me. An engine misfire will cause a vibration but there's all the other stuff to go wih it as in sounding like a diesel, etc.
If it happens only once the car is moving, look at anything that spins. Bad tires are #1 on the hit parade, if it's been sitting a long time and the tires have flat spots bumping the tire pressure to around 40 PSI and driving ~100 miles will get rid of a LOT of that. After that, if it's lessened but still objectionable either road force balance the tires or throw some new ones on it. Bent wheels can cause a nasty vibration, too. If it shakes the steering wheel bad, it's a front wheel. If you feel it shake in your butt more than the steering wheel, it's probably the rear.
Driveshafts typically do not shake until you are over, say, 20-25 MPH. U joints can cause this but again it won't do it sitting still or at very low speeds.
I have never seen a CV axle cause a vibration but that does not mean they can't. If the boots are still intact then you can pretty much rule them out.
Can you replicate the concern in neutral revving it at all
That's definitely not a normal thing for an FC 'vert- mine was far from perfect in many ways, but was always really smooth on the road. Tires could be the culprit, but the other things suggested could be as well. If you were closer, I'd happily drop a few decent condition axles your way if they end up being the problem (most of my engine stuff is S4 and not S5 though).
One thing I'm not sure I've seen mentioned (but then I'm WAY out of it this morning...) would be if it's badly out of alignment...
I have a few FC's. WE just got my wifes S4 NA coupe running again after sitting for a year. The tires were very flatspotted! It vibrated badly! However, it went away after a few trips around town.
I have had an FC vibrate from a bad driveshaft. It was almost unbearable! I had to change the driveshaft to solve the issue.
Rob R.
So it seems the issue may not be anything too horrible, but something I can hopefully solve with minimal effort. I bet it is wheel/tire related, and I think I will buy the car. Anyone ever replace a top on one of these models? I need to get a new top, and I can't see paying someone to do it when I am most likely capable.
If this site is anything to go by then replacing the top is certainly doable and maybe even a little easier than other 'verts:
http://www.convertibletopguys.com/convertible/862/1988-92-Mazda-RX-7#info-link11
Convertible Top Guys said:
Can I install this top myself?
Yes! Just keep in mind that the RX-7 convertible top design is unusual. Like most two-part tops, the RX-7 top features a front and rear section. But instead of integrating the two sections as is necessary with most convertible tops, the RX-7 front piece works more like a Targa top: A bar stretches across the top of the car. You attach the front section to its own frame and you attach the rear section to the top bar.
This type of installation makes the RX-7 convertible top one of the easier convertible tops to install. You will need to re-use your old window. Most Mazda RX-7 convertible top restorers are able to transfer the window section from the old convertible top to the new top.
Our Mazda RX-7 convertible top installation manual will walk you through Mazda RX-7 do-it-yourself installation.
http://foxed.ca/index.php?page=rx7manual#secondgen has the FSMs. 1989 FSM, Section 14 (body), page 73 is the convertible top removal/replacement section.
