Car jerks while stationery or idling.

[Tellmiwhy]

Hi Guys, 

 

I am driving a W204 pre-facelift model. Recently I noticed that the car jerks/vibrates intermittently while stationery or engine is idling. The RPM showed some fluctuation when this happen. Send the car to my usual workshop and a few stuff where replaced (spark plugs, air flow meter) but still the problem persisted. 

 

The boss suspect that it might be the ECU that is faulty but he advised me to send to C&C for a 2nd opinion as its rather costly to have it replaced. 

 

Just like to check if anyone had encountered such issue before and if so, what was the solution done to rectify this? The boss was telling me if there is no safety issue (as he sees it), I should probably try to ignore it to save $$. 

 

Any advice or recommendation will be greatly appreciated. 

 

cheers, 

Tellmiwhy 

[MarkCWQ]

Hi Guys,

I am driving a W204 pre-facelift model. Recently I noticed that the car jerks/vibrates intermittently while stationery or engine is idling. The RPM showed some fluctuation when this happen. Send the car to my usual workshop and a few stuff where replaced (spark plugs, air flow meter) but still the problem persisted.

The boss suspect that it might be the ECU that is faulty but he advised me to send to C&C for a 2nd opinion as its rather costly to have it replaced.

Just like to check if anyone had encountered such issue before and if so, what was the solution done to rectify this? The boss was telling me if there is no safety issue (as he sees it), I should probably try to ignore it to save $$.

Any advice or recommendation will be greatly appreciated.

cheers,

Tellmiwhy

Could be gear box or engine mount worn.

[Tellmiwhy]

I've changed the mounting at the last servicing which was 100km. 

 

I guess thats the reason the boss did not consider that might be the fault? I guess i will ask him to check my mountings again. 

 

It's bothering me for the past few weeks....  

 

Thanks for the advice!  

[catfish]

Hi,

 

If mounting issues, the car will vibrate during idle but the RPM should not fluctuate.(more on mechanical vibration problem)

Have you tried to play around with the gear, eg put the gear to N , P,  D & see whether problem go away/follow? (if GB problem)

 

Else It has something to do with air/fuel mixture during closed -loop...Usually the prime suspect is air flow meter related (eg dirty).. but since u already changed, next could be O2 sensor, it's piece of important 'feedback' sensor that manage right fuel mixture information to maintain steady idle rpm ...

 

regards

[Tellmiwhy]

The boss mentioned that whatever can be checked was checked thus the conclusion of the faulty ECU. Till now I am still facing this issue. 

Another bro here commented he faced similar issue and problem was due to the injectors issue. 

I am planning to discuss with the boss again to check through these two parts. 

Hope to have it resolved! 

Thanks for your advice.

 

 

[Creat1ve]

Problem solved by not turning on the air conditioning? 

[Tellmiwhy]

No, still face the same issue when air con is turned off. 

[machineoperator]

it might be your alternator pulley. I had same vibration issue and my mechanic found out it was due to the alternator pulley. Get it changed and it works perfectly. Hope it helps. But bear in mind I dun have fluctuating RPM issue though

[leo999]

i am on W203 and had similar problem since 4 months ago, did a full servicing inclusive of plugs change, gear box oil change..etc, still no improvement. 

in fact i did my fuel pump replacement as well still no improvement. and now air con also intermittment which lead to my mechanic suspecting that

RPM flutuation may be due to air con loading or something which i am urge to replace my compressor. Had already spent 3k trying to resolve this problem

which seem no end, so i left with 1. replace air con compressor 2. check alternator pulley 2. replace ECU but my car left 2 yrs HOW fellow MERC

 

[catfish]

Hi,

if due to aircond compressor loading, I guess you will notice a diff, with & without switching on the air-cond...if same problem persist, then it might not be compressor .. 

Also, did you notice any drivability problem? or only happen when car idle?

 

[kepiting1sg]

On ‎8‎/‎9‎/‎2016 at 6:02 PM, Tellmiwhy said:

No, still face the same issue when air con is turned off. 

Have you done a Diagnostic Check?

[leo999]

Thanks for the advise fellow MERCs,  Done a full dignostic twice at 2 different workshops and both does not reflect any fault. 

Those the mechanic suspect that it may be air con loading but the RPM flutuation, i activate and deactive the AC it does not 

seem to affect as the RMP still flutuate.  Since this 4-5 mths i do suspect that it maybe some sensors having problem or 

worst if there is a fuel sensor it having problem imagine i changed my fuel pump 3 time each last only 6-7 months. 

Perhaps if you folks can recommend a workshop that is willing to look into the problem i will deeply appreciate. thanks.

 

[kepiting1sg]

MBM - Sin Ming

Optimawerk - Upper Thomson

AutoSpritze - 1 Kim Chuan Terrace

[Tellmiwhy]

On 9/16/2016 at 10:00 AM, leo1621 said:

Thanks for the advise fellow MERCs,  Done a full dignostic twice at 2 different workshops and both does not reflect any fault. 

Those the mechanic suspect that it may be air con loading but the RPM flutuation, i activate and deactive the AC it does not 

seem to affect as the RMP still flutuate.  Since this 4-5 mths i do suspect that it maybe some sensors having problem or 

worst if there is a fuel sensor it having problem imagine i changed my fuel pump 3 time each last only 6-7 months. 

Perhaps if you folks can recommend a workshop that is willing to look into the problem i will deeply appreciate. thanks.

 

Can consider where i go because I find the boss is quite experience and his attitude is very gd. So far I've finally resolved my jerking issue and he was ok to let me trial and error with the parts and pay only when the problem is resolved. 

I don't rem his workshop name but its a workshop within the Shell Petrol station along bukit timah road. You can call him directly to ask: Richard: 9838 9819

cheers. 

[kepiting1sg]

20 hours ago, Tellmiwhy said:

Can consider where i go because I find the boss is quite experience and his attitude is very gd. So far I've finally resolved my jerking issue and he was ok to let me trial and error with the parts and pay only when the problem is resolved. 

I don't rem his workshop name but its a workshop within the Shell Petrol station along bukit timah road. You can call him directly to ask: Richard: 9838 9819

cheers. 

From your postings up to Monday evening no one solved your car jerking problem.

So finally this guy Richard solved your car jerking problem during these last 2 days.

From experience even if a spark plug misfired even once, the fault will come out in a diagnostic check and even telling you which cylinder spark plug misfired.

For the benefits of the forumers here, please share what eventually solved your car jerking problems when other workshops even CnC cannot diagnose your problem? 

[Odessus]

Yes please share your solution to benefit other forumers.