Engine vibration, droning, or shaking. Motor mounts related?
 

First the good things. It starts smoothly - hot or cold. Does not smoke on cold or hot under load/coasting/WOT.

Engine was not abused (a few thousand counts of Rev 1 range and just literally 2 ignition cycles on Rev 2 range).
Oil is OK.

110k miles, 2003, 2.7.

However, what I experience is some kind of shaking when coasting (kind of like jerking) and what most intriguing - weird almost like hard mount or metal to metal vibration at around 2100-2300 rpm. It goes away at 2400 rpm (completely). It is not there at 1800 rpm at all. In each gear (well, I tested 3, 4, and 5).

Another reason for mounts is that it is somehow ambient temperature dependent problem.

Sine it revs fine, power is there - I kind of excluded engine related issues.
I have not had a chance to put on a hoist to see the mounts, but that is where I am going to.

So what do you think it could be?


Oh, yeas, it is my freshly acquired Boxster that did not have PPI as... since I could not really find anyone to do that before my arrival, and it was a very cheap deal, so I checked all guts myself with crawling under the car.
But sure, unleash the missed PPI complaints... :D

And then advise what to look for.

I am planning on having post-PI. Maybe...

IMS - status unknown. Per previous owner - no indication on the filter.

Sounds like you have a durametric. Have you checked for codes yet? I have seen sometimes that durametric doesn't always show pending codes so maybe a generic reader with torque (torque always shows me pending codes)

I would get it hooked up and check misfire on each cylinder.

next would be to check rpm & cam1, cam2 deviation at idle. Just to see where it's at.

If it sounds metal to metal I wouldn't think it's a mount since those would be rubber.

And dont worry too much about a ppi. Even the best ones dont always find something. Something could of happened after getting it home.

I drove it 1000 miles since I put my hands on it.
900 miles of it was a trip from Boston, MA to Lansing, MI.
The sound did not really change except some variation with ambient temp. Somehow when warmer it would be "wider band" of the vibration, while colder - narrower and kind of like less present.

Since I had polyurethane filled mounts on my other cars, this is how it feels here.
At idle some of it, then gets smoother to hit a certain band (2.2k rpm) and gets smoother again. For me it felt like completely broken mount.

Also, what I see is a quite big movement of the gear shifter with load/coast changeover.

And one more thing. The exhaust pipes are very close, like just millimeters from the stabilizer bar. Normal?


As for durametric.
Yes, it is a rental that I have till Sunday.
I checked the cams and they are off by about 4 or 2 degrees. Not sure now, but I think at idle it was -1.0 and -2.7 OR +1.0 and -2.7 (hence 2 or 4 degrees difference).
Under different RPM they would nicely track each other and remain at about the same "spread".

No, no codes for the engine except the clutch switch, which is actually caused by the previous owner who... decided to bypass the clutch to start the car without the need to depress it.
I will not argue, maybe there was a need for it. I will; however, revert it back to normal, as it will definitely interfere with Cruise Control I am going to install.


I will check the Torque Pro and look for misfires under different engine speeds.
I was told the coils and spark plugs were replaced less than 10k miles ago.

use the durametric for the misfire, torque wont show those. It will show pending codes though as well as codes that are set.

Pictures of exhaust help, but that sounds about normal. It's tight in there.

if the clutch switch is bypassed it wont impact cruise, other then not disengaging it if you use the clutch. Not ideal but easy & cheap fix to replace if it is actually bad. Takes about 5 minutes.

Shifter is known to get play in it. There are several writeups on this and youtube videos.

With 110000 miles and 18 years old if the center motor mount has never been changed then it is most certainly toast.
The Rubber center brakes down rather quickly.
When I replaced mine on a 2000S with 47000 miles and the rubber center fell out when the mount was removed.
You can't really see the center of the mount via visual inspection while still mounted in the car. Not a difficult job but a hoist or lift makes it easier.

I did not see any pending codes on Torque.
I will check for misfires, but again, it does not feel like it is misfiring... I just did not get a chance to hook it up today.

I wanted to add more "description" of the vibrations.
So - sometimes it feels like the engine was not balanced. I am not sure if that is the best description, but feels like at certain rpms it would be bouncing. Again, like a wheel that needs to be balanced.

Then, the "metallic" noise, is not per say metallic. I was wrong saying that.
It is much more like driving over the highway rumbling strip. Kind of hard rumble. Of course, not to the same extent in terms of the force, but similar feel. And it is felt both ways - steady speed or coasting. Under WOT not so much, though. And only within certain rpm speeds - mainly 2200-2400.

Possible the PO put solid mounts in? Engine and/or transmission.

These are one of the more difficult things to describe in words so we are going to most likely throw out a bunch of things like my suggestion of checking for misfires/roughness.

Pull your motor mount....What you described sounds (to me) exactly what I experienced on a 1998 Box that I flipped years ago. The car ran great but seemed to have a 'rough' idle, along with a vibration ~3K rpm. Thing was, tac wasn't bouncing around at all. After changing plugs, cleaning maf etc with no change, I finally got around to replacing the mount. It felt like a new car.

I've done mount on other Boxsters as well, some of which had vibrations to a certain degree. Every car had a torn mount.

The heat shield between exhaust and body shell does make something like this resonating noice - at least mine did. Slight bent of it (just few millimeters) by hands fixed the issue. Lifted the car, tapped slightly to the heatshiled with rubber hammer and slightly bet it untill the noice disappeared. BTW, do not bent it to lean against the bodyshell or bumper.

Similar sound but a bit more metallic can come from resonating vertical heat shield between gear likage at transmission and muffler and can be 'repaired' in a same way.

I have the same feeling on my 2002 2.7 except I get it at 4000 rpm. Oddly I used to also get it at 2000 rpm, but that randomly went away and the 4000rpm vibration at the same time lessened. Everything checks out on mine with no codes at all.

I still have not checked for misfires, but I will get to it this weekend.

Thanks for all the replies. I hope with help of a little mirror I could inspect the front mount.
The sides, or rather tranny mounts, are oil filled. How one can tell if it is shot? I did not really see any oil tracks, but they could have been shot for a while and all oil was washed off. Especially that I drove about 500 miles in rain and about 150 in snow. Heck, beginning of May and it was snowing in OH...
Anyway, the nuts appear to be the original ones (the torx type).

Finally, so there are two side mounts, one for the engine - what is in the back then? There seem to be a cradle or something going towards the bumper.
I did not have a chance yet to crawl under to inspect.

Further update.

Darn it. Ramps are too short to allow me for a good inspection of the front motor mount.
I need to get the car lift. Wife may not agree...

Anyway, tranny mounts look OEM (aka original ones).
Engine mount - as I said - I could not reach it.

The intake and exhaust, both sides - they are basically spot on and they track right away. Barely any difference (0.5 degree?).

Misfire - from a cold start till a few miles after a full warm up with a couple of WOT at different RPM and steady states - no misfires at all.

Engine shakes like it was allowed to rock front and back. Sometimes it feels like towing a trailer. I guess GoPro like setup is needed. I might use webcam and observe it.

so, next step is the mounts.

drive behind your wife and look at the tail pipes, if they move up or down when applying power (or releasing it) it is the front engine mount.. It is fairly easy to replace and you will find a step by step procedures on this forum.

I have a new insert left over from my 987 if you need it (Lemfolder..?) , but you will need to remove your front mount and take it to a tire shop (or a friend with a press) to remove the old insert and install the new one.

Good luck

... and if you need to replace your water pump... with the mount out it is much easier. ;)

+ 1

Yes indeed, this would be a great opportunity to replace the water pump and the thermostat