Juddering Idling

[KillerHERTZ]

I have noticed over the past week when I stop at traffic lights etc my idling revs are just above 500 RPM on the dash when normally it should be just below the 1000 mark?

Also, it seems to be fluxuating up and down slightly (you can feel the car almost juddering ever so slightly).

The performance of the car has not been effected at all, I havent noticed any changes and I have done the best part of 400 miles this week.

Any ideas? it had an A service 2 weeks ago.

EDIT AFTER 5 YEARS - THIS WAS FOR MY W202

 

[Dieselman]

HT leads or MAF would be the first thoughts, followed by and air leak.

 

[KillerHERTZ]

Cheers, MAF is 4 years old, so hopefully its not that...

 

[DRBC43AMG]

May be an idea to see if you have any fault codes. That could/should point the way to solve the problem

 

[Pendragon]

I have noticed over the past week when I stop at traffic lights etc my idling revs are just above 500 RPM on the dash when normally it should be just below the 1000 mark?

Also, it seems to be fluxuating up and down slightly (you can feel the car almost juddering ever so slightly).

The performance of the car has not been effected at all, I havent noticed any changes and I have done the best part of 400 miles this week.

Any ideas? it had an A service 2 weeks ago.

Snap !...I have the same car with the same problem and I have spent over £600.00 on parts but still the same.............so, if you find out what it is please post back so I can check mine out without wasting any more money.

No fault showing on diagnostics by the way, so totally baffled.

Keith

 

[KillerHERTZ]

Snap !...I have the same car with the same problem and I have spent over £600.00 on parts but still the same.............so, if you find out what it is please post back so I can check mine out without wasting any more money.

No fault showing on diagnostics by the way, so totally baffled.

Keith

Can you let me know what avenues you have already explored?

 

[Pendragon]

I run a diagnostics business so I did my own. I replaced: Plugs, all coil packs, both o2 sensors, MAF, HT leads. I also did a thorough engine flush, a engine decoke, compression test all good.

I did find that the oil breather pipes and air inlet (pinholes) were filthy and pinholes blocked and cleaned them out and it did run slightly better but it is still the same as yours is now.....very frustrating as I have checked every possibility for air leaks. I have run another diagnostics test and it is showing absolutely nothing wrong. Have spent over £600.00 so far and no closer to solving the problem.


Keith

 

[Pendragon]

Just to also add, had the injectors checked and tested....all fine. Had the engine apart just in case it was a burnt valve....all fine.

Petrol and Match is now springing to mind !

Let me know if you find out exactly WHAT the problem is.

This seems to be a common problem on a lot of pre 2001 C class models with shed loads of members on here posting about the same symptoms yet I have not found one that has cured it.

Keith

 

[Mr B.]

what are the most common faults on the 1996 c 200 sports?

 

[KillerHERTZ]

what are the most common faults on the 1996 c 200 sports?

Please create a separate thread rather than make this one go off topic.

 

[martyz]

Have you done a fuel rail pressure test,if the fuel pressure regulator is not holding true,you would have some form of spluttering that would be more evident at idle.

 

[KillerHERTZ]

Have you done a fuel rail pressure test,if the fuel pressure regulator is not holding true,you would have some form of spluttering that would be more evident at idle.

Not done anything at all yet, will get it down my indy in the next week or so.

Just done another 300 miles today, seemed to run better than ever aswell

 

[DRBC43AMG]

Particles in the petrol which managed to get by the filter or come from elsewhere in the fuel line, perhaps
Could be just a morning touch of blues

 

[Terry_]

If there are no faults except for a slightly lumpy idle [ and no faults logging on star] then you need to check the actual values screen at idle. You may find the only value out of spec is air intake temperature which could be raised. If this is the case then the egr valve is not sealing off correctly.

I have had this little bugger of a fault a couple of times now.

Hope this helps guys

 

[Pendragon]

I doubt its the petrol, well not on mine anyway, since I run on LPG.

Just been outside on put my Star on it and still no faults showing.


Keith

 

[Terry_]

I doubt its the petrol, well not on mine anyway, since I run on LPG.

Just been outside on put my Star on it and still no faults showing.


Keith

Did you check the actual values? A fault does not get logged. Check the values scren at idle and look at the air intake temperature

 

[Pendragon]

We had the engine apart purposely to check the valves and they are all fine.


Keith

 

[Terry_]

So you have a lumpy idle? Everything else is fine? car drives perfect? No misfiring?

Star is logging no fault codes.

So you know that the exhaust gas recirc is operating perfectly as it should with the engine at idle? You dont have to take the engine apart to check this

 

[SL300-24]

I think that he must have misread your last post

 

[Pendragon]

I did and I will.

Keith