1993 Z-28, LT-1, auto- tranny, vibration appears when the car is parked, in neutral, and the engine RPM is raised above idle, or to about 1,600/1,800 RPM's. It feels as though the engine is sitting on the frame. The center console and dash vibrate to the RPM's of the engine. If I bring the RPM's up into the mid 2,000 to low 3,000 range the vibration goes away somewhat. However this engine "growl" can still be felt thru out the cars body. I dont think this is normal. The car has 115,000 miles and I dont think the mounts have ever been changed. It is not a miss or bad wire or anything like that. Its a definite vibration. What I suspect is that the rubber portion of the motor mounts may be worn/broken/dry rotted and the metal parts of the mounts are touching together, the frame part to the engine part.

While driving the highway the other night I put the car in neutral going 75 MPH. The engine, while going 75, was turning about 1,800 RPM's. The vibration was there. However once in neutral the vibration went away and only the normal road noise and bumps were felt. NO drive train vibrations were felt!

Does anybody have any suggestions as to why the vibration is there or am I correct in assuming the mounts are bad? I also thought at one point that the harmonic balancer was bad. Could that be part of the problem too? This engine vibration is really weird......and getting on my nerves!!!

Thanks for your insight.

Jeff

 

Come On guys! Can someone offer a tip or agree or disagree with my diagnosis, please!

I am about to buy the mounts, about $80 a piece, and put them in, about a full days work. And I sure would hate to do this and still have my vibration problem.......

Your suggestions are greatly appreciated in advance.

Jeff

 

I have the same vibration problem with my car as you. I haven't checked my mounts yet. For a while I have been thinking that the engine itself had a problem, but possibly it is the motor mount.

Make sure to post again if you change them!


Didn't you post this question on here a while back? Was this your daughters car or something? Maybe I'm thinking of somebody else...

 

I have sold motor mounts, and I always have a slight vibration. But its only mostly noticible in idle, if I am crusing you really cant tell. Is the vibration being caused by a broken trans mount?

 

95Z/28 LT1, your right it was my daughters car. And I am still having the same problem as I am driving it more these days. As you might remember she went off to college and I bought her a brand new Civic. I had posted a "for sale" post on the Z-28 but I think that I have decided to keep Camaro and sell my 1987 300ZX. Either way both are very nice cars. So if you know of anybody looking for a nice black 1987 300ZX........have em drop me a line at Boeing717Driver@aol.com. The car is in Charlotte, N.C.

I am still having the vibration problem as noted above. I drove the car to ATL and back and its just getting worse. I already put a new tranny mount in as that one broke a year ago. Its still good. But the vibration in the engine seems so strange. Its almost like the flywheel either threw a weight, the harmonic balancer is bad, or like I posted I am thinking the engine mounts are just dry rotten and need to be replaced. Any of the above items, or combination thereof, could be causing the problem. But I think the mounts are most likely suspect. UNLESS someone reads my post and points me in the right direction.

Thanks for your reply.......

Jeff

 

Mine does a similar thing, it has about 80k on it now. I am about to change mounts because I believe mine are sagging. BTW you can get poly mounts from Summit for $40 a piece vs. 80.

I believe part of my problem is due to my headers, the passenger side header hits the A-Arm on the suspension and this creates some annoying noises and vibrations, but even before my headers I had the same thing in my dash.

My engine also has a slightly rouger idle than before which I don't think helps, and my only guess is that it's ignition related.

Sorry I couldnt be more help, will let you know how the mounts do when I put them in.

 

Summit huh? Thanks for the heads up. (I can remember when motor mounts were like $25.00!! Geesh......$80.00+ a piece! What is Chevy thinking???)

Oh well..............Yes, if you do put on the poly mounts and your vibration subsides please let me know.

Jeff

 

The vibration that you describe is exactly what my car has been doing. It's almost like a harmonic or something, the way it will make the car vibrate. It's like a vibration that will pass through the car, if that makes any sense. It will even shake the steering wheel a little bit, or make the console vibrate. And it's ALWAYS at about 1600-1800 RPM. Then it tapers off a bit and still continues, gradually getting worse the further I rev it.

I have had my engine checked with a scope at a shop because I though there might be a problem with the engine like a burnt valve or ignition miss, but nothing stuck out. It feels like a miss, but it won't vibrate the car when it is just idling. It just happens when I start coming off idle. Also, I have a M6, so we might be able to rule some parts out with that. The strange thing is that it started after I changed my clutch. Maybe it is an engine balance problem?

I have heard that Chevy talks briefly about an engine "wobble" in their service manual, and recommends rotating the harmonic balancer in 90 degree increments to try and remedy it. I haven't tried that one yet...

Make sure you keep us posted!

Jacob

 

Oh, and one more thing. When I changed the clutch and the vibration/harmonic problemc started, I changed back to my old pressure plate thinking that it was the problem and the new PP screwed up the balance of the engine. But when I swapped back in my old pressure plate with a just a new disc, the vibration never went away.

 

an speed (rpm) variant vibration is caused by something not being balanced. this happened at work- and almost caused a catatrophic disaster.
check to make sure your harmonic balancer is ok, flexplate is on good ect ect
"that driveshaft balanced?"
"should be"
"doesn't look it"
"we'll see"

1000rpm- ok
2000rpm- still smooth as silk
3000rpm- silk
3300rpm- the whole building shook
3900 rpm- all better

 

95Z, your description was better than mine. The vibration DOES feel like it travels the lenght of the car body and ossilates up and down in intensity. I guess we know what each other is feeling. Thanks for your more detailed gouge.

Anyway, I might try the harmonic balancer thing, ie 90 degree turns to see if that helps. Then I guess I might tighten the bolts on the flywheel and see if that thing flung a weight. Then if that fails I guess I'll invest the time and money in the mounts.

Boy, I sure hope that one or all of these things STOP the vibration. I am so focused on it when I drive the car that I dont enjoy the power and handling of the Z-28 anymore. Go figure. Like I said I have a 1987 300ZX too that has about 165,000 miles on it. That little Nissan V-6 is sooo damn smooth that you cant even feel it running. And those mounts are original. I guess the Japs have a pretty good handle on "vibration technology".

I'll keep you posted on my vibration saga and if anybody else has the same vibration please share your thoughts too. There are obviously alot of us that have this problem.

Jeff

 

TTT

 

TTT

Ever figure this one out?

 

Nope. I never did actually figure it out. I still think its the engine mounts. I believe both new mounts will stop the harmonic vibration.

However I think I am just going to sell the car instead. Along with this 93 Z-28 I also have a 87 300ZX. I intend on selling them both so that I can hunt down an older Vette, 80/81 model. If anybody is interested in either car I will post them on the board for sale. Nice package if you ask me!

E-mail me if your interested in more details and pics of either car: Boeing717Driver@aol.com

PS: What the heck does "TTT" mean???

Jeff

 

Awww, c'mon man, don't sell it. That's too bad that you want to get rid of it. But, I know how it is sometimes.

I took my motor mounts out yesterday when I was pulling the oil pan, and one of the mounts was bad (ripped). They were both pretty spongy too. Not really that hard to get to either. Hopefully this vibe will be gone once I button everything back together. I'll keep you posted.

Jacob

BTW, TTT means To The Top.