Glen

Drive the crap out of it.

slant911

I wouldn't think that a washing would knock things out. It is relatively "water-proof". It does suggest (at least to me) that a cracked coil is all the more a possibility because a cracked one would allow water in and mess with things.

However, it is cheap to just go and do an "Italian tune-up" as suggested above

If that doesn't work I'd start looking at spark plugs/coil packs.

jleev

I like the thought of the 'Italian tune up'. Brilliant in concept however where might one actually perform this delicate operation with out getting arrested? My average bloody MPH in LA is 32!! A crime really for this machine.

slant911

You need to get out of town a little Maybe a quick trip to LV at 2:00 A.M.

jleev

2am or not I'll be waiting for the Valentine to arrive prior to tune up!

dustinr

I notice it also, maybe it's because I'm used to a smooth throttle response from my old car, but my Turbo is a little jerky. Like you say, I notice it when coming off of the throttle just a little bit and I associated that with the waste-gate suddenly dumping off boost. I also notice a slight miss every once in awhile whilst traveling at a constant speed. I just figured it's another quirk of a exotic car. I just had the 30K done and my car only has 25K on it, and they did replace the spark plugs and it still does it. Maybe we can nail down some similarities... my car is a X50, I live at roughly 4500 feet altitude, I like windy walks in the park, and my cats name is Remi...haha. (joking) Seriously though, my car does it too.

jleev

Good morning dustiner,
Very interesting.........those symptoms you describe sound uncannily familiar.
Were your coil packs checked/tested when the plugs were done? Did the mechanic drive with diagnostics attached in order to ID misfire or other codes?

Best,
J

Aerodude

Sorry to revive this thread -- but I've noticed the same thing in my '03 TT. It's very subtle, but definitely noticeable. More so when cruising in a lower gear (e.g. 4th as compared with 5th or 6th), and when I let up from light throttle. Any more thought or insights? Or maybe this is just 'normal'?

Receiver

I've been trying to chase this down for 6 months. I've replaced plugs, coil packs, MAF and had the ECU rebuilt. Also have had the entire system tested for leaks and it's still there. I'm begging to think it's normal. Anybody have anything to add?

PAULUNM

There's a thread on renntech describing this as a possible variocam issue- either a bad solenoid, broken solenoid bracket, or a oil passage for the variocam plugged up...

Seems that A LOT of these cars have this hesitation...

Macster

If the behavior is very subtle chances are it is normal. At light throttle the engine controller can not only adjust valve timing but adjust lift as well, by selecting the low lift portion of the lifters to cut down on emissions, improve fuel economy. The low lift feature allows cuts down on the parasitic loss due to the engine having to fight to get air past a barely open throttle butterfly valve, barely open in low speed operation cause of course the engine's air needs are low.

In this state of possibly adjusted valve timing and valve lift the engine may not be as responsive as it would be otherwise. Responsiveness is sacrificed for better fuel economy and lower emissions.

I try to avoid running the engine at too low an rpm in the higher gears to avoid engaging this low lift feature to mainly avoid wear/tear on this hardware. Porsche I read somewhere tested this hardware to 250,000 cycles, but I plan on driving the car many many miles and that 250K cycles doesn't seem too high to obtain. Thus, generally I strive (and it ain't hard...) to keep rpms above 2K when in 4th gear or higher.

Also, I have observed that the Turbo's e-Gas operation is not as linear/smooth as my 02 Boxster's e-Gas operation which has many many more miles on its e-Gas.

Lastly, the Turbo's engine is just not as tractable at low rpms as the Boxster's engine. The Boxster engine can operate at 1K or thereabouts even in 3rd or 4th gear as long as I don't make huge torque demands upon the engine at least until the engine has gained some rpms. The Turbo engine kind of lets me know it prefers a bit more rpms, and I oblige it.

Sincerely,

Macster.

Macster

Update. I tried driving the Turbo at low rpms in higher gears last night, and didn't encounter any jerkiness or anything out of the ordinary only that at say at around 1500 rpms or bit lower in 4th gear the car/engine/exhaust/?produces a noise that just makes me want to avoid doing this.

I can't say where the noise is coming from and it doesn't sound like engine is tearing itself apart and there are no other symptoms or untoward engine behavior, but the car (engine?) is letting me know it prefers more rpms.

One WAG on my part is there is some low engine speed/high load condition that produces a harmonic vibration in the exhaust system or some underbody heat shields that accounts of the noise. The noise doesn't appear to be coming from inside the engine, combustion chambers, and does not in any way I am faimiliar with sound like any kind of misfire.

The noise is not present down to 1K in 1st or a bit higher in 2nd and a bit higher yet in 3rd.

Now I did encounter a bit of jerkiness -- although this is too strong/negative a word for what I did feel -- in 6th at low rpms operation (around 2K rpms) but this was from the boost coming on and going off again. At a steady throttle on level road there was no boost but any up grade or even a bit of throttle to pick up speed to keep up traffic would have 0.1bar boost showing. Concurrent with the boost appearing the car would kind of give a bit of a surge (naturally) and concurrent with the boost ending there'd be a bit of a desurge (?).

So, I'm not sure what you are experiencing is normal or abnormal. Save for the boost coming and going -- and I didn't see boost at rpms lower than 2K in any gear but my testing was not exhaustive -- and the car reacting noticably but still in a mild fashion, my 03 Turbo is quite tractable at low rpms even in higher gears with that hard to describe noise the only real symptom.

The Boxster driving under similar conditions and at even lower rpms doesn't generate or produce the noise.

Generally, a rule of thumb I use is that if the desired speed is under 20mph I use 1st gear, 20mph to 29mph I use 2nd (or 3rd) and 30mph to 39mph I use 3rd (or 4th) and so on.

This results in the engine seldom operating at very low rpms in the higher gears.

Sincerely,

Macster.

Aerodude

Thanks for the insight. For me, the "jerkiness" is actually more noticeable at lower gears and higher rpms, but with light throttle. For example, if I'm in 4th gear at highway speeds, I notice more jerkiness if I get on and off the throttle quickly and lightly I can even year an audible (very light) thunk sound when I tap the throttle. Any ideas or similar experiences. I'm wondering whether there's just a lower limit where the e-gas cuts off or on (compared with an analog throttle) and the responsiveness at a lower gear is just more noticeable (compared with my other cars).

Macster

What you are now describing is more like the play in the drivetrain making itself known.

Every CV bearing or gear set in the drivetrain has its clearance. They have to have this to last. The amount of this clearance from assembly to assembly and thus car to car can vary due to normal and permissible (and acceptable) manufacturing differences.

In some cars these permissible variations stack up to cancel each other out and the vehicle exhibits little drivetrain play and little thunk noise when treated as you described.

In other cars these permissble variations stack up and increase the overall amount of drivetrain play. In such vehicles as these the vehicle exhibits more drivetrain play and produces more of that thunk noise under some operating conditions.

In short, the noise is normal. My advice would be to avoid generating the noise if at all possible. I do not consider myself but average in this respect and I don't have any problem driving the car in a manner to nearly eliminate this thunk noise. My Turbo can produce this thunk -- though it is not as severe as other (non-996 Turbo) cars in which I have encountered it -- but I learn how to drive the car to avoid causing this noise. It is not hard, in my opinion.

Anyhow, the noise is mating components (but with some operational clearances) hammering against one another. These components are tough, made of strong and hard alloy steel, but you want to limit the number of times you cause them to hammer together.

Or the noise may not be normal. There's always the possibility that since I can't experience the noise the symptom that it falls outside of what would be considered normal, or that my concept of normal is not accurate.

Thus one piece of advice I can offer is to have the car checked out by a qualified/experienced tech that knows this particular flavor of car and see what his opinion of the noise is. Normal? Or not normal?

There was at least one owner how reported his Turbo's cardan shaft (the shaft the drives the front diff) had way too much play and was making some noises. The shaft/bearing assembly was bad.

Sincerely,

Macster.

Aerodude

Macster,

Thanks for the insight and great explanation. I may mention it at my next service, but I think it's too subtle to bring in special or to try and chase this down. I freely admit that I'm probably over sensitive to these kinds of things. I've noticed things before that I've brought up to the mechanic, only to feel like an idiot when I go for a test drive with him and realize how hard he's strainng to hear or feel what I do ;-). Also, as my wife will attest to, I'm the guy who's always trying to figure out what that darn rattling sound is in the car (and it turns out to be the pen in the glove compartment).

Happy Driving!