I have always been amazed at the utter turbine like smoothness of my 89 930. Whether at idle or full throttle, it seems like zero engine vibration makes it into the ****pit.

My 996 TT, however, vibrates like a cheap Korean 4 cylinder with no balance shafts. Not scary, just that slight buzz, particularly at idle.

For anyone who has driven both an air cooled car and a 996 TT motor, is this normal, or should the 996 be as turbine smooth as an air cooled turbo? Is this likely a symptom of plugged injector or bad wires? I would think any boxer 6 layout without balance shafts would have the same smoothness.

 

I'm not too familiar with the air cooled cars but my 996tt shakes / vibrates a good deal.

 

Mine is very smooth with little to no vibration, its stock low mileage. I have had about every sports car there is and its comparable. I have driven low mileage 993s when shopping and my car was quieter smoother= but I do love the air cooled.

 

Thanks. Interesting. I bet something is off about my stock 996 tt 19000 miles. Plugged injector from sitting too long? I always assumed the boxer 6 and the dry sump was the reason for the smoothness, and the 996tt has both.

 

Mine vibrates a little more than my 50k mile boxster. I will know for sure though after changing out the transmission mount.

 

When mine was stock I thought it was extremely smooth. My previous car was a 996 C2 and it was a bit rougher at all ranges and when I first started driving the turbo it almost felt too smooth. The idle is noisier on the turbo but that is down to engine design and is completely normal.

 

No air-cooled Porsche experience, but I can tell you compared to my 02 Boxster my idle of 03 Turbo is a bit rougher at cold start but the Turbo engine idle gets smoother once warm to the point that while it is still rougher running it is not enough rougher running to cause me any concern.


While warming up I can hear faint backfires from the exhaust. Signs of an overly rich mixture. This is to feed unburned fuel to the converters to get them warmed up quicker.


Also, this rich mixture is combined with shortly after cold engine start the DME engages VarioCam Plus, the intake valve low lift feature. I can tell when this happens as the engine makes a bit of a stumble and the oil pressure gage needle makes a bit of a dip then quickly recovers as the DME switches the low lift feature on.


With this intake valve low lift in effect the idle is a bit rougher but as I mentioned above once warmed up the Turbo get smoother but still not as sewing machine smooth as the Boxster engine.


Absence a CEL and misfire error codes, or some other odd behavior I think you are just experiencing the Turbo engine's rawness. Remember the engine is only 3.6l and yet develops 420hp. (With my 06 GTO it took 6.0l of V8 to produce 400hp.) Did you expect Caddy smoothness -- at least at idle -- from a 3.6l 420hp engine?

 

Drove mine today extremely smooth and absolutely no stumbles etc at start up.

 

I have both and from what you describe, there is something wrong with your 996.

There are no wires unless you are referring to the ones leading to the injectors. Otherwise, it sounds like you are referring to a distributor which the 996 does not have.

First thing I would look at is the motor mounts.

 

Interesting. Are motor mounts a common problem? Also, I've been reading something about needing to change plugs and coils at the first big service around 30 miles, no?
Any other common issues?

 

I have both as well and there maybe some drivetrain vibrations the engine is pretty damn smooth. It makes the normal noises on start-up which would send a luxury car guy into shivers but that is normal. My 930 is pretty smooth as well but I would not call it a turbine!

 

my dad had a 930 for a number of years, until he sold it last year.
I had a lot of driving miles in it.
930's do have a slightly 'smoother' feel from the drivetrains as the engine crank and flywheel/clutch assembles are much heavier and act as dampers. Also I suspect the CIS injection being relatively richer-running also creates a smoother combustion cycle.
NVH in the chassis is light-years better in 996's than 930's....

 

This is most noticeable at idle, and a little bit with power on, so it's gotta be mounts or engine rather than rotating drivetrain. The car is a Tiptronic. I wonder if that is why it idles a little rough with a little load on it.

I'll get all that looked at when I get the turbos/intercoolers/exhaust/engine tune/transmission tune done.

I sure do prefer the sound of my 930.

 

Look for leakage on motor mounts. Most people change out plugs at 30k service the coils are inspected for cracks. I would put new coils in while changing plugs as they are not that expensive and these cars are getting up in years.

 

My LWFW rattles slightly at idle and a little more if the ac is on but I could really care less. Why does a little noise bother people so much? I kind of like the noise. It's comforting and reminds me that it's not a boring car like my Lexus. Just saying.