W222 S350 Rough Idle When Engine Warm

[Jim85]

Hi all,

I have a S350 which has on occasions been idling rough and then sometimes has cut out, noticed it is happening on long runs once the engine has warmed and the car comes to a stop. It happened on the weekend, after pulling into the services and stopping, the revs don't fluctuate very much, but it does make the whole car shake when this happens, before cutting out.

The car has been to an independent garage, and there are no fault codes, and there are no lights on the dash, has anyone else experienced this, or know where to start looking? Weird thing is that it doesn't happen all the time, have put some redex through, but its still happening.

Any advice is greatly appreciated.

 

[DSM10000]

Hi all,

I have a S350 which has on occasions been idling rough and then sometimes has cut out, noticed it is happening on long runs once the engine has warmed and the car comes to a stop. It happened on the weekend, after pulling into the services and stopping, the revs don't fluctuate very much, but it does make the whole car shake when this happens, before cutting out.

The car has been to an independent garage, and there are no fault codes, and there are no lights on the dash, has anyone else experienced this, or know where to start looking? Weird thing is that it doesn't happen all the time, have put some redex through, but its still happening.

Any advice is greatly appreciated.

Welcome!

Did the independent garage (presumably a Mercedes specialist) use Star to look at live engine values?

Does the car have a full service history?

 

[Jim85]

Welcome!

Did the independent garage (presumably a Mercedes specialist) use Star to look at live engine values?

Does the car have a full service history?

Hi,

Firstly thanks for replying.

The car does have full MB service history.

I am not sure if they looked at live engine values.

I have just got hold of a fault code reader which shows a pending code P0191 - Fuel Rail Pressure Sensor A Circuit Range/Performance. Could that possibly be the issue?

 

[DSM10000]

Possibly.

Do you know if they used Star to diagnose? Star is really the best way (with someone who knows how to use it) to get to the bottom of problems like this.

OBD codes such as the one you have found are generic. Star will be able to look into systems and sub systems in much more detail.

 

[Jim85]

Possibly.

Do you know if they used Star to diagnose? Star is really the best way (with someone who knows how to use it) to get to the bottom of problems like this.

OBD codes such as the one you have found are generic. Star will be able to look into systems and sub systems in much more detail.

Ye they have star as they are a Merc specialist, but the code wasn't showing up then, even now it is just a pending code. Have emailed them letting them know, and will wait to see what they say.

Looking up the symptoms of the fault code, they match with what is happening, when it does play up, such as engine hesitating on idle and cutting out, so hopefully this will lead us to the cause!

 

[kendohog]

Possibly.

Do you know if they used Star to diagnose? Star is really the best way (with someone who knows how to use it) to get to the bottom of problems like this.

OBD codes such as the one you have found are generic. Star will be able to look into systems and sub systems in much more detail.

Looking for someone with Star in Glasgow - Vito Brabus ESP warning message... Can you help?

 

[DSM10000]

Looking for someone with Star in Glasgow - Vito Brabus ESP warning message... Can you help?

A quick Google shows these : glasgow mercedes specialist - Google Search

 

[Jim85]

Possibly.

Do you know if they used Star to diagnose? Star is really the best way (with someone who knows how to use it) to get to the bottom of problems like this.

OBD codes such as the one you have found are generic. Star will be able to look into systems and sub systems in much more detail.

The fault has occurred more often now, with the EML coming on. The car has been to the independent today, and Star gave codes P008FA & P0088E2, fuel pressure too high.

They said whilst the fuel system was being tested the test aborted when it got to component Y94 (quantity control valve). Whilst it would seem it is that part, they said it can't be said for definite, and that they can't just order the part and try it, incase it doesn't turn out to be that.

Based on what Star has brought up, is that component a common issue on these and is it worth just changing it and hoping for the best?

Another thing noticed is that the engine never revs past 3000rpm when stationery, is this just a limiter to protect the engine when stationery, or could it be linked to the fuel pressure issue?

 

[DSM10000]

The rpm limit when stationary is normal and is, as you say, there to protect the engine.