I've dome some reading here around the engine idle shake and it seems to be easy enougt to fix with engine mounts. I just wanted to make sure my situation fell under the same phenomena.... When the heat/air conditioning is off I get enough vibration that the passenger seat visibly shakes. As soon as I turn the AC on everything smooths right out. Does this sound as though new engine mounts would cure my situation?

 

I have the same issues...very interested in the cure...

 

Y don't u check your pulleys , if ones is shot , it could shake the engine and car

 

Engine mounts... Replaced mine about 3 weeks ago diene to the same reasons... Oh what an improvement

 

Perfect....thanks ToFast that's exactly what I was hoping for.

 

A little bit of shake is perfectly normal, but not excessive. It's present on just about all 996's I've sat in. Especially early models.

I don't want to spoil the party but the mounts might not help significantly.

Engine and trans mounts certainly can contribute if they are tired. You can visually inspect the engine mounts easily. If you see fluid coming out of them or if one of them looks to be lower than the other then it has failed. The transmission mount is more difficult to diagnose and can be very difficult to replace depending on your model year.

Other ways to help keep the vibration in check. These steps are less expensive and easier than replacing your engine mounts and they might provide more improvement than new mounts.

Oil level 3/4's full (check when engine warm, given 30 minutes to drain)
New spark plugs
Clean air filter
Clean the throttle body (and idle air control valve if you have a 99 C2)
Run a bottle of Techron through the fuel and use quality gas
A good high RPM drive at operating temperature

If it's still vibrating just as bad as before, you might have a vacuum leak or your mounts could in fact be gone.

 

Logray, thanks for the tips.... I do have a 99 C2 so I will certainly run through those... Oil, filter and plugs are done.... But hadn't thought to cover the others you mentioned. It just seemed peculiar that since the idle vibration goes away as soon as soon as the AC/heat is turned on that this was a classic case of the mounts no longer taking out the lower frequency vibration they were designed to. Indicating they were probably toast. I should double check to see if they are leaking or if one is sitting lower than the other. I did notice yesterday that the right side tail pipe was sitting lower than the left. We shall see.

 

The '99 likes to shake a little at hot 680 RPM idle. I completely rebuilt my engine and had it balanced and it still shakes ever so slightly (albeit no where near as much as it did before the rebuild).

If one of your mounts is gone one of your exhaust tips will be lower than the other, unless they are both shot.

Other than that, if the mounts are 13 years old, they could be "tired", and you might notice an improvement, and even bigger payoff if you follow the other steps I pointed out.

Still though, if you thoroughly clean your throttle body and idle control valve, you should notice an improvement (especially if you remove the T/B and also dismantle the IACV to get them really good and clean internally).

 

1 more thing would be tranny mount. You wouldn't believe how bad they were. There was about 1/2 inch play sidetoside.

 

Did the engine mounts and what a difference. Night and day. The shop that did them also checked the trans mount. It was fine. The MAF was still throwing a code even though I cleaned it so that was replaced as well. Might have something to do with the improvent as well. No she's running great along with new stab bar links. Looks like its time to sell now. Up on autotrader she goes!

 

Y u selling it? N I guess I was right..

 

Only reason I am selling is I want something quicker. The car runs absolutely perfect right now. Almost questioning whether to sell it with such low mileage (54K). The Porsche experience has been fun, but, living here in michigan and right off of Woodward, honestly it's mostly about straightline speed. In fact Sunday heading North on I-75 I had a new 5.0L mustang filled with peiple tailing me on an on-ramp from 696. I dropped a few gears, gased it and pulled over a few lanes to get away from him.... I kept my foot in it for while, he gained on my quickly and had me within a dozen seconds or so. That was kind of the last straw for me. My budget doesn't allow for a supercharger or to upgrade to 911 turbo. So sadly for now anyway, it looks like I will be out of the Porsche game. Since I work for GM I might be rolling into late C5 or an early C6. The other option was a heavily modified Solstice/Sky.