Yet another vibration @ idle

[lp01]

Dear Xoutposters,

I've done some considerable research on this issue but there seems to be no unique, objective causes to this issue. My car is a 2001, FA71 with a 3.0 diesel engine.

Here's what I found concerning this particular vibration:

-It happens only when stopped, foot on brake and gear "D" ~(600 rpm); the vibration is sometimes audible;

-In "P", "N" or "R" it does not happen, although in "R" there is a slight vibration not present in "N" or "P"; nevertheless this vibration is not audible. Whether in "P", "N" or "R", the engine idle speed is ~660 rpm

-It does not occur when car is in a positive inclination slope (only flat or negative inclination)

-There are days when it occurs and others it doesn't; not related with outside temperature though, as far as I have noticed.

-Vibration is not sensible to A/C settings, meaning I can turn it on or off with no impact on it; besides, the A/C does not influence the idle rpm at all. The engine control seems to "compensate" for the A/C immediately.

So... I have 2 questions:

Question 1. Since the engine is idling at 600 rpm in "D", as opposed to 660 rpm in all other gears, do you think this could be the cause?

Question 2. Independently of the low idling rpm being the cause or not, is it possible to raise ~50 rpm when the transmission is engaged in "D" without affecting the rpm in all other gears?

Thanks in advance for your input . I have scheduled a visit to a dealer within one week, but I would like very much to have your insights on this issue.

Cheers

[jst2878]

i have a similar vibration intermittently. when i hold the brake in drive i get a funny vibration, not sure what it could be

[KingCon]

Mine comes and goes. Seems to be worse when stopped at an incline with the a/c on. I've found that letting the X warm up first seems to help.

[Weasel]

At the dealer through the GT1 the idle speed is adjustable, and it can be raised in 10 rpm increments so 660 would be doable.

[lp01]

Thanks Weasel. The possibility of adjusting within 10 rpm intervals is really impressive!

Nevertheless, will the dealer be able to do it (raise ~60 rpm when in "D") keeping constant the idle speed when engaged in "R", "N" and "P"?

In your opinion, having a different idle speed when in "D" and "R" is normal?

(today I spoke a little bit about this problem with the dealer that will receive the car within 10 days and he told me they never touch the idle speed, etc, etc. I'm glad this site exists, 'cause I will insist with them to increase the idle speed )

[Weasel]

It is a very uncommon thing as it is almost never needed to be done, which is why most don't know about it. In that service function there are multiple areas of idle you can adjust, like in neutral, in gear, when ac on, at higher electrical load, etc. The tech that gets your vehicle may learn something new.