Engine Vibration around 1900 RPM

Rainer · #1 (**permalink**) 12-03-2006, 02:06 AM

Today, I noticed a slight engine vibration around 1900 RPM. It starts at around 1850 RPM and disappears at about 1950 RPM. It can only be felt when the car is standing still (not when driven) and it occurs with the manual transmission in neutral with depressed and non-depressed clutch pedal. Engine temperature (cold or warm) doesn't affect it either.
The vibration is very small but it can be felt in the seat. The symptom doesn't have to be new - I just never revved up the engine slowly enough to have enough time to actually notice it.
Does anybody else have this symptom, or am I the only one?
I would really appreciate some feedback, because my Porsche dealer is 290 Miles away and I would hate to drive all the way to Albuquerque just to be told that "they all do that".

nick664 · #2 (**permalink**) 12-03-2006, 01:29 PM

i dont have the exactly the same problem but a similiar two:

when slowing down, with 1, 2 or 3 gear engaged, and the rev needle passing 1200 rpm there´s a "bump" in the transmission (the car sorta jerks..). can anyone try doing this and tell me if they feel anything.
second: my car (ca 8.000 km) has developed a prominent vibration (somewhere in the engine or the drivetrain) between starting from 2.000 rmp. worse when cold.

what to do when the diagnose unit of the dealer doesnt show anything??

regards,

nick

p.s all comment very welcome!!

**Gator Bite** · #3 (**permalink**) 12-03-2006, 02:18 PM

Quote:

when slowing down, with 1, 2 or 3 gear engaged, and the rev needle passing 1200 rpm there´s a "bump" in the transmission (the car sorta jerks..). can anyone try doing this and tell me if they feel anything.

Just a theory, but often times with Bosch fuel injected cars, if you come completely off the throttle the Motronics will stop feeding fuel to the engine all together, effectively shutting it down. This is done to save fuel, add some torque braking and reduce emissions. It only happens above 1,200 RPM and when the engine falls below this point the Motronics brings the engine back to life by feeding it fuel again. This reduction in torque brake resistance can be felt if you pay very close attention.

You may very well be feeling this transition. If the 'bump' you are feeling is very light, almost like you need to pay close attention to feel it, this is probably what you are feeling.

Rainer · #4 (**permalink**) 12-03-2006, 02:50 PM

Thanks for the response Nick.
I don't quite understand your second issue. You write "between starting from 2.000 rmp. worse when cold".
Between 2.000 RPM and ???
It could potentially be similar to mine with just a slight upshift in RPM.

Since I didn't get any other responses on this site, I have to assume that nobody else has this problem.
I have sent my issue to the Technical Committee member in charge of the Boxster, Cayman (986 & 987) area of the PCA.
Will post the outcome here.

Freestyle · #5 (**permalink**) 12-03-2006, 08:51 PM

Guys I get the same metalic vibratio noise when coming off the throttle from around 2,500 rpm down thru 1,500 rpm. It only happens when its cold (below 80). Should we be worried?

**JackWood** · #6 (**permalink**) 12-03-2006, 09:02 PM

The metallic vibration at 2000-2200 rpm when the engine is cold (below 80) is always the pressure release valve in the oil pump. Take it in to the dealer straight away and tell the dealer there is a Technical Service Bulletin about this issue. They will replace the valve in the oil pump.

Jack

Rainer · #7 (**permalink**) 12-03-2006, 09:45 PM

Freestyle and JackWood, thank you guys for your comments!
My vibration is, however, NOT accompanied by any kind of metallic sound. It's just a slight vibration that can be felt in the seat.
Do your cars actually vibrate or are they just producing the metallic sound?

I probably wouldn't even be too concerned about it were the car not totally vibration-free in the remainder of the RPM-range. I'm actually worried that it might be the announcement of a clutch-related issue (as you know, many of the folks here had insufficiently torqued flywheels).
I think I would have never noticed it had I not checked the RPM-correlation between the reading of my latest toy, the “Gtech Pro RR”, and the car's tach. In the process I increased the engine RPM very slowly to compare the readouts. That's when I caught the 1900 RPM vibration.

nick664 · #8 (**permalink**) 12-04-2006, 09:58 AM

Rainer: i meant that the vibration starts at 2.000 RPM. And its much more noticable when the engine is cold. The vibration is not metallic, and i too feel it through the seat.

Have you tried to test my "first issue" with the slowing down?

Freestyle · #9 (**permalink**) 12-04-2006, 01:31 PM

K. Car booked in to have it inspected. They confirmed it is either the valve or the pump and will check.

nick664 · #10 (**permalink**) 12-04-2006, 03:24 PM

@freestyle: how did they find out? with the standard Porsche diagnose computer?

**Gator Bite** · #11 (**permalink**) 12-04-2006, 04:01 PM

Quote:

Originally Posted by nick664

@freestyle: how did they find out? with the standard Porsche diagnose computer?

A computer won't help them with this. This particular malfunction is entirely mechanical, and it's a known issue.

Would you like to read the Technical Service Bulletin? It's right here in the file library.

**JackWood** · #12 (**permalink**) 12-04-2006, 06:09 PM

Rainer and Nick,
Your vibrations do not sound like the oil valve. They just sound like an engine balance thing. Yes my car does run "rougher" in the lower RPM range when stationary and worse when cold. It always has. As the revs rise the engine becomes smoother.

Jack

nick664 · #13 (**permalink**) 12-04-2006, 08:55 PM

i went to the dealer, and the diagnose computer showed nothing.

sounds really mechanical. problem is that these things do not show up on the diagnose unit of the tech, thus "no error message on the diagnose unit = problem not existent". ....just hate it.