W208 Idle Not 100% Smooth

[steveoelliott]

Hi all,

I have a 2000 W208 CLK 230K, with 76K.

For a while it has not idled 100% smooth. If you watch the rev counter, it doesn't sit steady and you can hear the engine (if outside the car is not silky smooth).

I've changed plugs, leads and coils but no difference. I then cleaned the MAF (no oil / gunge in this part of the snorkle anyway) but still not any better.

I even tried disconnecting the MAF in the thought that the default mode would highlight a potential issue with the MAF. Although without it, it idled worse, kind of expected I guess.

Any suggestions?

 

[steveoelliott]

Any ideas? Are there any other sensors that may be at play?

 

[flango]

has it always been smooth or is this a change from the norm?

 

[Dieselman]

Try cleaning the throttle body with carburetor cleaner.

 

[jotter22]

hat did you clean the MAF with?

Tony.

 

[steveoelliott]

I used some alcohol based spray, Video 40.

 

[steveoelliott]

For cleaning the throttle body, do you mean just spray the carb cleaner around it?

 

[A1EK]

For cleaning the throttle body, do you mean just spray the carb cleaner around it?

If the car is running a little lumpy with the revs slightly climbing and falling at idle could well be the MAF. However despite the fluctuation the engine should'nt sound any more noisy? Are you just referring to the increase in engine note as the revs rise etc, but not a rattly sound?
If you disconnect the MAF sometimes this can show and improvement , do the revs stay still (Around 750rpm ) when you disconnet the MAF? Sometimes however if you disconnect the MAF the car will not run and this is often down to the build of muck in the throttle body where the car has had to adapt and learn over the years and when you disconnect the MAF its just to far past what the engine can interpret.
To clean the throttle body, just remove the 3 hex screws on the right of the engine and you will see the butterfly valve. IF dirty then you can use a little soft tooth brush with some carb cleaner or something similar to remove the build up, and wipe away with a cloth. The car after you start will then start to learn the new butterfly position as it may have been impeded before.
When you cleaned the MAF was there any/much oil? if there was oil, then you may have some blocked breather nozzles that go into the intake of the engine, There are write ups on clearing this. I would recommend cleaning as it will only get worse. There should be no oil at all around your MAF.

 

[steveoelliott]

I'll have to take a look at the throttle body then... Will this really make that much difference though? It's a big area to get clogged but it's certainly worth a shot.

MAF was fine and no trace of oil in that section of the snorkle. Bear in mind though on the 230K the breathers and everything are before the airbox and therefore prior to MAF so I think it would have to be really bad to make it's way all the way over here.

 

[steveoelliott]

Oh and it is a sligh flucuation. Probaly 50-75 rpm. Some people would say wtf am I worried about but it should be smooth Felt more than heard and seen on the needle if examining carefully.

 

[flango]

Oh and it is a sligh flucuation. Probaly 50-75 rpm. Some people would say wtf am I worried about but it should be smooth Felt more than heard and seen on the needle if examining carefully.

Mines not Smooth Either And I Have Never Driven A 230 that Is Hence My Earlier Post Has It Ever Been smooth Mines Had The Maf And Many other Components changed And Its Had Expensive Dynamic Diagnostics On It And All Values Read Normal So I,ve Put Mine Down To A Characteristic Of The Car And Stopped Worrying

 

[steveoelliott]

Perhaps I should do the same... Mine has always been like it since owning it.

 

[A1EK]

I'll have to take a look at the throttle body then... Will this really make that much difference though? It's a big area to get clogged but it's certainly worth a shot.

MAF was fine and no trace of oil in that section of the snorkle. Bear in mind though on the 230K the breathers and everything are before the airbox and therefore prior to MAF so I think it would have to be really bad to make it's way all the way over here.

Trust me I have a the same car and the breather pipes I'm talking about Are about 10 mm in diameter and attached onto nozzles that are about 3mm and go into the fuel sidegrees of the engine. You can't see them from above, but if they get clogged it causes oil to be sent back into the air intake system. However it seems you have no oil so you're fine.

 

[A1EK]

Perhaps I should do the same... Mine has always been like it since owning it.

I would say bottom line your car should be smooth what ever the revs. Mine is smooth from 1mph to 150mph however I get a slight wobble at 60mph but this is down to lowering and tyre make at 64mph it goes away. Personally reading this post I would put all my money on yoit MAF you may think it's okay but you need to try another one to be certain.

 

[steveoelliott]

Yes ideally, I would change the MAF or swap with a known good. Problem is finding a donor

It's only ever at idle.

 

[A1EK]

Yes ideally, I would change the MAF or swap with a known good. Problem is finding a donor

It's only ever at idle.

One other thought, when you say the car does not idle smooth and the revs move up and down, does the engine sometimes seem as if it stutters? or are the revs smooth up and down?

I once had an issue on a W210 E Class and the problem was a slight shorting from the end of the plug that fits onto the spark plug. There was a slight tear and dust had built up causing a slight spark to jump across to the body. However you said you have new wires and plugs so I doubt this an issue.

 

[steveoelliott]

It revs up and down fine. Issue only present at idle.

 

[steveoelliott]

I stuck some cataclean through this since it is slated to clean the O2 sensor (amongst other things).

It mas made a noteworthy improvement. Not 100% but I am going to put another bottle through in the next month or so.