Kickdown - rpm increases but not sufficient acceleration
09-26-2014, 12:29 PM
#1
Junior Member
Thread Starter
Kickdown - rpm increases but not sufficient acceleration
The car is 2011 S350 with 25K km (16K miles). For the past few days I am observing the following:
1. Kickdown or sudden throttle results in rapid increase in RPM but doesn't gain speed like I was used to. It does reach good speeds but feels lethargic combined with quick rpm increase. The difference is not very obvious but I am very sure it is not how it used to be.
2. There is a high-pitch noise (like a toy battery radio car on full acceleration) above 3K rpm. The same noise can be heard even if the transmission is in neutral when I press the accelerator hard. The noise gets mixed up with RPM noise so not easy to prove.
3. Under normal gentle acceleration (say below 2.5K rpm), everything is normal and I can reach 120kmph and above speeds. If I drive sedately, the car feels absolutely normal at all speeds including stop-and-go traffic.
Sent to the dealer, they ran the diagnostics and took a long test drive and returned the car saying everything is OK. How can I find a "smoking gun" proof for the existence of this problem. The dealer techs I am afraid are not too bright or they made up their mind that I am hallucinating.
Few questions:
1. If it is transmission slippage issue, can the high-pitch noise occur when I apply throttle during Neutral also?
2. How come the diagnostic tool doesn't throw errors? My guess is that the dealers believe anything that is not reported by diagnostic tool is not a problem.
3. How do I prove that the acceleration is below normal and RPM increase is above normal?
Thanks guys. I hate when dealer thinks I am hallucinating :-) I am also having a suspension noise while going over humps which I am not able to duplicate (happens only during the first few minutes of early morning cold weather)
1. Kickdown or sudden throttle results in rapid increase in RPM but doesn't gain speed like I was used to. It does reach good speeds but feels lethargic combined with quick rpm increase. The difference is not very obvious but I am very sure it is not how it used to be.
2. There is a high-pitch noise (like a toy battery radio car on full acceleration) above 3K rpm. The same noise can be heard even if the transmission is in neutral when I press the accelerator hard. The noise gets mixed up with RPM noise so not easy to prove.
3. Under normal gentle acceleration (say below 2.5K rpm), everything is normal and I can reach 120kmph and above speeds. If I drive sedately, the car feels absolutely normal at all speeds including stop-and-go traffic.
Sent to the dealer, they ran the diagnostics and took a long test drive and returned the car saying everything is OK. How can I find a "smoking gun" proof for the existence of this problem. The dealer techs I am afraid are not too bright or they made up their mind that I am hallucinating.
Few questions:
1. If it is transmission slippage issue, can the high-pitch noise occur when I apply throttle during Neutral also?
2. How come the diagnostic tool doesn't throw errors? My guess is that the dealers believe anything that is not reported by diagnostic tool is not a problem.
3. How do I prove that the acceleration is below normal and RPM increase is above normal?
Thanks guys. I hate when dealer thinks I am hallucinating :-) I am also having a suspension noise while going over humps which I am not able to duplicate (happens only during the first few minutes of early morning cold weather)
Last edited by androdev; 09-26-2014 at 01:09 PM.
09-27-2014, 07:59 AM
#2
Junior Member
Thread Starter
This is the sound from my car during kickdown at 20 kmph (I feel there is a high-pitch noise in addition to the engine revving):
Here is something I found on youtube as a reference.
Doesn't it sound like my car has high-pitch noise?
Here is something I found on youtube as a reference.
Doesn't it sound like my car has high-pitch noise?
10-08-2014, 03:59 AM
#3
Junior Member
Thread Starter
The problem was identified as a faulty idler pulley, fixed under warranty by the dealer. Rest of it was my imagination 
I still wonder why it failed within 26K km (16K miles).
I still wonder why it failed within 26K km (16K miles).
10-31-2019, 02:48 AM
#4
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2010 S500 GCC
Hi, Was the faulty pulley affecting the acceleration of the car and the acceleration thing got ok after fix?
