Engine Vibration on deceleration

[zugvogel]

Hi,
my 2000 Boxster that I have owned now for about 4000 miles is showing a slight engine vibration at around 2950 RPM. The car has 73500 miles on it now.

The vibration is not noticeable when accelerating and just barely noticeable when cruising. But every time when I decelerate with the foot completely off the throttle the engine does vibrate quite noticeably. Decelerating when slowly letting the throttle out is causing less to no vibration.

I did talk to a classic VW shop owner a few months ago and he mentioned that Boxsters are notorious for failing flywheels, something I have not heard before or since or seen here on this forum, but it sounds like a plausible explanation.

I am reluctant to just have the engine ripped out but on the other hand this could be something quite serious and better get taken care of before something really bad happens. What would be the best way to deal with this?

[racer]

Check motor mounts.

[zugvogel]

quick update: I just jacked up the car and took a peek at the motor mount. I know usually you can't really see if the rubber is cracked without removing the mount, but from what I saw, that mount is shot... I saw the rubber being gone on both sides, left and right in one spot, so I just ordered a new one. I could see the beginning of the part number and it started with a 986 so I assume it has never been replaced before.

However...... with the engine cold I revved it up to the usual 2950 RPM and gee, that engine was shaking. Given that the mount is most likely completely shot, I am still wondering if that much vibration is normal or if something else is wrong. Oh well, the new mount will go on in 2 days and then we shall see....

[zugvogel]

Final update:

WOOOOW!

ok, serious now... I followed Wayne's instructions found here:
Pelican Technical Article: Replacing Motor Mounts - 986 Boxster (1997-04) - 987 Boxster (2005-08)

and took my Boxster for a little spin. I can not believe the transformation of the car. First of all the vibrations that got my nerves rattled so badly are completely gone - no sign of engine shake at 2950 RPM anymore. And whats even better, on our poorly maintained streets here in SoCal, I used to have this horrible KLONK everytime I crossed a railroad track or a small pothole. That horrible KLONK is now gone too - so I don't have to rebuild the suspension either!

I can not remember having spent $140 on a car which had such a big impact.

Here is a picture of the old engine mount, which was indeed the original one, manufactured in 1999. There was hardly anything left keeping the center attached to the outer ring:

[racer]

Wow.. I'd say that old mount is a little worn

Glad to hear after your fix you enjoy the car again!

[Wayne 962]

Cool deal, glad the article was of help!

-Wayne

[Zeke]

I've mentioned/complained about the vibration between 2900 and 3K a few times here and never heard anything back except that my induction system must be off due to the ECM not working properly due to any number of reasons like a bad O2 sensor.

Well, now it seems maybe all these puppies vibrate (I have a 2.7). I'll be checking my original (50,000 miles) motor mounts this week end.

[BerneseMtnDog]

I had heard somewhere that a failing motor mount will produce a vibration around 3K. My 2.7 is doing this now so I ordered a new mount and we'll see what the old one looks like. I've got 84k miles on my 2000.

Steve

[Wayne 962]

We took a look at the transmission mounts today, and found that with the lowering of the drivetrain and the use of the 993 mounts, they may be tapping against the rear upright. We'll be doing some more testing tomorrow, but this a somewhat unique problem to this car.

-Wayne

[zugvogel]

Based on my experience I'd really recommend it. It is not only dependent on mileage but pure age as well as the mount is made of rubber.
Replacing mine took a bit over an hour.

[Wayne 962]

Originally Posted by Wayne at Pelican Parts

We took a look at the transmission mounts today, and found that with the lowering of the drivetrain and the use of the 993 mounts, they may be tapping against the rear upright. We'll be doing some more testing tomorrow, but this a somewhat unique problem to this car.

-Wayne

Yes, this was the problem. The 993 mounts I used are longer so that the drivetrain can be lowered. But, these were hitting on the lower part of the upright, so we shaved some of the ends off.

-Wayne

[BerneseMtnDog]

Replaced my motor mount yesterday and it looked exactly like zugvogel's. Also same drastic improvements noticed Hopefully the newer updated mount will be more robust. Car is a 2000 2.7L with 84k miles.

Steve

[harryrcb]

guess what guys, I have a 04 S and had to replace the motor mount at around 40k . which seems early but why I looked for it was that I got wheel hop with hard acceleration. I dont remember any engine vibration and the mount did not look as bad as the one above but it was definitely torn.