Irregular idle

[MBZ4LIFE]

Hey Guys
Have a minor problem that I need help with. My W202 C230K sport idles irregularly. It seems that the rev counter is jumping up and down when the car is in neutral. Is this a commin occurance or is there something wrong. On pull away all is fine except for a slight delay. Any advise will be greatly appreciated as I am a novice when it comes to this.

 

[Bobby Dazzler]

Sounds like MAS/MAF to me.

 

[television]

I do not think that the MAF affects idle

 

[MBZ4LIFE]

I have gone through most of the threads with regards to MAF and MAS would like to know if this is the same item or is there a difference between the two. Tried to find a thread with pics preferably that explains how to remove the MAF I think for cleaning to see if this might erradicate the problem. If you guys know where I can find these threads or could possibly supply me with the link it would be great.

 

[Bobby Dazzler]

If my understanding is correct, the MAF/MAS that's giving fluctuating readings (rather than consistently 'out' readings), then it could lead to an unstable idle.

 

[MBZ4LIFE]

Bobby thanks.
Does this means it needs to be replaced or is there a simpler less costly alternative. MB parts in South Africa are very, very expensive specially for older models.

 

[Bobby Dazzler]

MAF/MAS is the same thing (Mass AirFlow Sensor).

Another similar phrase is MAP (Manifold Air Pressure) sensor, performed a similar function in older engines.

 

[Bobby Dazzler]

Bobby thanks.
Does this means it needs to be replaced or is there a simpler less costly alternative. MB parts in South Africa are very, very expensive specially for older models.

MAF/MAS problems manifest themselves in all sorts of ways, quite often a loss of power. Disconnecting the sensor can be a good way of diagnosing the cause, as power should be resumed, albeit the engine will be a little rough (less smooth).

However in your scenario, because you have no loss of power (bar the hesitation you mentioned) disconnecting the sensor may not help much. Worth a go though.

I wonder whether your sensor might not be giving the ECU a reading at all based on what you've described.

Anyone think Oxygen sensor may be a fault here?

 

[recycled]

I do not think that the MAF affects idle

it does on start up.

 

[television]

it does on start up.

I still do not think that it does,,on cold start the temp sensor and starter energize the cold start fuel enrichment device.

 

[recycled]

mine did. on cold starts it backfired like a burst balloon and it idled like crazy from 2000- 500 rpm. when warmed it was ok. until i changed it, then the cold starts just went back to normal.

 

[jamesmc]

My car was misfiring on startup and the tick over would fluctuate. A new MAF fitted and those symptoms went. The whys and wherefores I am unsure about, but it's fact that those problems were resolved with MAF replacement.

I sourced my MAF through eBay via a German seller (Genuine Bosch unit with warranty seal).
http://search.ebay.co.uk/_W0QQsassZcarpartsberlin
Cost was about GBP£160.00 including shipping to Portugal.
They do say they will ship worldwide.

As said often enough in this Forum... when buying from eBay don't go for a cheaper non Bosch branded substitute as they will let you down or not work at all.