Bad Vibrations
09-02-2005, 10:42 PM
#1
Junior Member
Thread Starter
Join Date: Feb 2004
Posts: 15
Hello folks, I really need some help from some of you rotary gurus. My s4 tII is shaking very badly. I'm lazy, so I dont really want to retype all this stuff.
Please see this post:
http://www.teamfc3s.org/forum/showthread.p...&threadid=43354
If anyone can help, please reply here or at the other forum.
Thanks in advance
Please see this post:
http://www.teamfc3s.org/forum/showthread.p...&threadid=43354
If anyone can help, please reply here or at the other forum.
Thanks in advance
09-03-2005, 02:24 AM
#2
Senior Member
Join Date: Feb 2003
Location: Rainy Seattle
Posts: 452
Hrm. You've got quite a conundrum there.
I'm sure you've checked for lack of spark although I don't remember reading it.
If it's got good compression and the rest is good I don't see what else it could be other than a counterweight problem.
side note: There's no way that's the original engine with that much poop on that mileage.
The only shaking rotaries I've come across have had compromised apex seals in one chamber.
I'm sure you've checked for lack of spark although I don't remember reading it.
If it's got good compression and the rest is good I don't see what else it could be other than a counterweight problem.
side note: There's no way that's the original engine with that much poop on that mileage.
The only shaking rotaries I've come across have had compromised apex seals in one chamber.
09-03-2005, 03:38 PM
#3
Junior Member
Thread Starter
Join Date: Feb 2004
Posts: 15
[quote name='HeffSpooled' date='Sep 2 2005, 11:24 PM']Hrm. You've got quite a conundrum there.
I'm sure you've checked for lack of spark although I don't remember reading it.
If it's got good compression and the rest is good I don't see what else it could be other than a counterweight problem.
side note: There's no way that's the original engine with that much poop on that mileage.
The only shaking rotaries I've come across have had compromised apex seals in one chamber.
[/quote]
Thanks for the reply Spooled. I haven't checked for lack of spark, but I have replaced both coils, plugs, and wires. By check for lack of spark do you mean take the plug leads off and watch for a spark while trying to crank? The thing will idle all day without dying. When I bought the car with around 118k the original owner told me the motor had never been replaced. I took it to Mazda and they did a compression test on it. The lowest face was 7.9, and they told me I would be looking at buying a new motor soon. I know it's high mileage for a turbo engine, but I have heard stories of people going for longer - not by much though. I don't think my problem is a seal, the car runs fine and has plenty of power. I'm going to try replacing mounts even though they "feel ok" when I rock the motor. I don't know what else to do.
I'm sure you've checked for lack of spark although I don't remember reading it.
If it's got good compression and the rest is good I don't see what else it could be other than a counterweight problem.
side note: There's no way that's the original engine with that much poop on that mileage.
The only shaking rotaries I've come across have had compromised apex seals in one chamber.
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Thanks for the reply Spooled. I haven't checked for lack of spark, but I have replaced both coils, plugs, and wires. By check for lack of spark do you mean take the plug leads off and watch for a spark while trying to crank? The thing will idle all day without dying. When I bought the car with around 118k the original owner told me the motor had never been replaced. I took it to Mazda and they did a compression test on it. The lowest face was 7.9, and they told me I would be looking at buying a new motor soon. I know it's high mileage for a turbo engine, but I have heard stories of people going for longer - not by much though. I don't think my problem is a seal, the car runs fine and has plenty of power. I'm going to try replacing mounts even though they "feel ok" when I rock the motor. I don't know what else to do.
09-03-2005, 05:58 PM
#4
Senior Member
Join Date: Feb 2003
Location: Rainy Seattle
Posts: 452
By check for lack of spark do you mean take the plug leads off and watch for a spark while trying to crank?
The thing will idle all day without dying.
When I bought the car with around 118k the original owner told me the motor had never been replaced. I took it to Mazda and they did a compression test on it. The lowest face was 7.9, and they told me I would be looking at buying a new motor soon. I know it's high mileage for a turbo engine, but I have heard stories of people going for longer - not by much though. I don't think my problem is a seal, the car runs fine and has plenty of power. I'm going to try replacing mounts even though they "feel ok" when I rock the motor. I don't know what else to do.
As far as the comment about needing a new engine soon. B.S. !! That's a good engine. See my above comment about how well they run on low compression. Although hot-start flooding is a given. Oh and I dyno'd 197whp with that engine @ 10psi on a stock S5 turbo and stock exhaust.
I honestly don't know what to tell you about the problem at hand. Something's got to be done. If it were me I think I'd have to tear off the front cover and see what's goin' on.
Cheers
09-04-2005, 02:16 AM
#5
Junior Member
Thread Starter
Join Date: Feb 2004
Posts: 15
[quote name='HeffSpooled' date='Sep 3 2005, 02:58 PM']Yes, just to confirm, although "plenty of power" pretty much rules out this kind of stuff. But it's shaking violently right?
It doesn't shake noticably at idle. It's not until I give it some gas that it feels like I'm going to break something. Closest thing I can compare it to is like a broken driveshaft going down the highway, but does this sitting still.
That's pretty damned amazing from what I know about TII engines. I had one that I'm pretty sure only had around 140k mi. on it and it probably had comp#s in the 4.5 range. When I started playing with it I walked that line just once and chipped up an apex seal. I've got another engine in there now that is hella strong, much more than the old one, and it's only making less than 7.0 (kg/cm2) or in the 90's psi-wise.
When I first purchased the car - I took it to Mazda and that's when I got the 7.9 kg/cm2 number for the worst side. This was a huge bargaining chip for buying the car. I wound up literally stealing this car. In the couple years I have owned the it, I have redlined it quite a bit and never felt any noticable loss of power. It has however started burning a lot of oil in the upper RPM range. I wish I could warrant getting another engine, because I know it's on it's way out. The recent compression test I did to try and rule out the engine as being my shaking problem, was done while cranking the engine cold and looking at a regular psi compression tester. It showed 90-90-90 on both housings give or take 1 PSI. With these numbers, I really don't think the engine is causing the shaking, and not to mention, if something was damaged inside the engine I would expect it to tear itself apart very quicky. If there was something wrong with the front counterweight, would I be getting such good compression numbers?
As far as the comment about needing a new engine soon. B.S. !! That's a good engine. See my above comment about how well they run on low compression. Although hot-start flooding is a given. Oh and I dyno'd 197whp with that engine @ 10psi on a stock S5 turbo and stock exhaust.
I thought it was B.S. too. You made 197whp on the 4.5 kg/cm2 motor? That is very amazing.
I honestly don't know what to tell you about the problem at hand. Something's got to be done. If it were me I think I'd have to tear off the front cover and see what's goin' on.
I really don't know what's involved in removing the front cover, but I can imagine it is a major PITA. Can you give me any tips on this procedure? I still have a few loose ends to tie up. I want to check the timing. A friend of mine was telling me that when a CAS fails, it can do all kinds of strange things. I also want to replace/inspect the motor mounts. I really can't tell if they are good or not. Someone I know had a mount that was split, and his car didn't shake anything like mine does, so I'm not very confident that replacing the mount will solve the problem. I'm under the impression that I can just unbolt the mounts and raise the engine just enough to remove the mounts to inspect them. Please correct me if I am wrong about this. Another thing worth mentioning is that the bushing/mount on the transmission crossmember was cracked on one of the "legs". I went ahead and installed it because it didn't seem to have excessive play to me. Also the differential mount is starting to give way, during hard launches it would "clunk". Could any of these mount be causing shaking as bad as I've described?
Thanks for all your suggestions Heff. Sorry for the long-winded response, but I'm hoping some other members will chime in with some ideas I've yet to try.
[/quote]
It doesn't shake noticably at idle. It's not until I give it some gas that it feels like I'm going to break something. Closest thing I can compare it to is like a broken driveshaft going down the highway, but does this sitting still.
That's pretty damned amazing from what I know about TII engines. I had one that I'm pretty sure only had around 140k mi. on it and it probably had comp#s in the 4.5 range. When I started playing with it I walked that line just once and chipped up an apex seal. I've got another engine in there now that is hella strong, much more than the old one, and it's only making less than 7.0 (kg/cm2) or in the 90's psi-wise.
When I first purchased the car - I took it to Mazda and that's when I got the 7.9 kg/cm2 number for the worst side. This was a huge bargaining chip for buying the car. I wound up literally stealing this car. In the couple years I have owned the it, I have redlined it quite a bit and never felt any noticable loss of power. It has however started burning a lot of oil in the upper RPM range. I wish I could warrant getting another engine, because I know it's on it's way out. The recent compression test I did to try and rule out the engine as being my shaking problem, was done while cranking the engine cold and looking at a regular psi compression tester. It showed 90-90-90 on both housings give or take 1 PSI. With these numbers, I really don't think the engine is causing the shaking, and not to mention, if something was damaged inside the engine I would expect it to tear itself apart very quicky. If there was something wrong with the front counterweight, would I be getting such good compression numbers?
As far as the comment about needing a new engine soon. B.S. !! That's a good engine. See my above comment about how well they run on low compression. Although hot-start flooding is a given. Oh and I dyno'd 197whp with that engine @ 10psi on a stock S5 turbo and stock exhaust.
I thought it was B.S. too. You made 197whp on the 4.5 kg/cm2 motor? That is very amazing.
I honestly don't know what to tell you about the problem at hand. Something's got to be done. If it were me I think I'd have to tear off the front cover and see what's goin' on.
I really don't know what's involved in removing the front cover, but I can imagine it is a major PITA. Can you give me any tips on this procedure? I still have a few loose ends to tie up. I want to check the timing. A friend of mine was telling me that when a CAS fails, it can do all kinds of strange things. I also want to replace/inspect the motor mounts. I really can't tell if they are good or not. Someone I know had a mount that was split, and his car didn't shake anything like mine does, so I'm not very confident that replacing the mount will solve the problem. I'm under the impression that I can just unbolt the mounts and raise the engine just enough to remove the mounts to inspect them. Please correct me if I am wrong about this. Another thing worth mentioning is that the bushing/mount on the transmission crossmember was cracked on one of the "legs". I went ahead and installed it because it didn't seem to have excessive play to me. Also the differential mount is starting to give way, during hard launches it would "clunk". Could any of these mount be causing shaking as bad as I've described?
Thanks for all your suggestions Heff. Sorry for the long-winded response, but I'm hoping some other members will chime in with some ideas I've yet to try.
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