Unsteady idle on 200 CDI (2001), when warming up...

[pentax]

Hi all,

Problem is following: a bit unsteady idle when engine is warming up, at coolant temperature aproximately from 30*C - 60*C. NB!!! Problem is appearing only at outside temperatures +5*C and lower. Above +5*C, not a sign of a problem.

Detailed description: Perfectly (cold)starts even at otside temperatures below zero (did it also with one non working glow plug), working after it fluently until up to that moment, when temperature indicator bar starts to show coolant temperature (equal to 10 minutes driving). After it idle becomes unsteady. Nothing bad really (no hard shaking), not more than about +/- 50 rev per minute, and few mm of tachometer moving. If then engine reaches normal temperature, its work perfectly again and remains perfect. Even if it cooles down to 30*C-60*C after use.

Service for the car has been done lately - all filters, glow plugs, oil has been changed. This has`nt influenced all that. Havent been in engine diagnistics yet - I thought I ask here first for any similar experiences and solutions. Thanks in advance!

PS! If it`s matters anything - car has just 67000 km`s on it.

 

[Parrot of Doom]

I have a similar problem, feels like a misfire. It only happens when cold, and I'm presuming that its my EGR valve. It got a lot better once I cleaned it out. Search the forum for EGR, you'll find my thread. Might be useful.

 

[pentax]

Yes, exactly - like misfire.
I have already read your EGR post with a lot of nice pictures . Thank you for such an informative post! As much I can figure out, EGR could be the main cause to suspect here, but of course there may be something else. After you did the EGR cleaning - did your problem disappeared or just only got a bit better?

By the way, at the moment we have 4 CDI cars in Estonian MB Club forum with the same problem. Those who has been in engine diagnostics, telling that according to diagnostics injectors and electrical part of engine are OK.

 

[Parrot of Doom]

No, it got a lot better, but the problem persists. Another symptom was 'surging' at certain speeds on the road, usually around 30mph. Also, accelerating from 0mph can sometimes be uncomfortable.

I may have another go at it one day.

 

[Dieselman]

My first thought would be an injector not spraying properly, after that MAF or as you think EGR or intake manifold flaps.

I'd still put my money on blocked injector though. Try a strong dose of injetor cleaner before doing anything else.

 

[pentax]

Could be an injector, yes. But again - it perfectly starts when cold and works about 10 minutes without any hint to misfire. And why it all appears at outside temperature under 5*C ??? That makes me think, that sticky residue in EGR valve is influencing its work (cold=solid, warm=more liquid); when engine is warm, it works again normally... Nonexpert suppose of course, may be I am totally wrong

I will do a try with Redex Diesel Plus, as it was positively mentioned in this forum and they also sell it in our country. After it I will look further. By the way, with every tank of fuel I am constantly using a dose of Stanadyne diesel additive - so in principle all fuel system should be clean...

 

[Dieselman]

Could be an injector, yes. But again - it perfectly starts when cold and works about 10 minutes without any hint to misfire. And why it all appears at outside temperature under 5*C ??? That makes me think, that sticky residue in EGR valve is influencing its work (cold=solid, warm=more liquid); when engine is warm, it works again normally... Nonexpert suppose of course, may be I am totally wrong

I will do a try with Redex Diesel Plus, as it was positively mentioned in this forum and they also sell it in our country. After it I will look further. By the way, with every tank of fuel I am constantly using a dose of Stanadyne diesel additive - so in principle all fuel system should be clean...

Standyne is good stuff so as you say it should be OK.
You can check your own injectors if you remove them
Connect them to a garden pressure sprayer or similar and then apply 12v to the solenoid connections. You should see a fine mist with no dribbling.
This is a good way to clean deposits.

 

[Parrot of Doom]

If you're going to bung fuel additive in, try first removing the fuel filter, emptying it, and pouring the additive directly into the filter. To the brim. It gets a good strong dose that way.

 

[mioba]

If you're going to bung fuel additive in, try first removing the fuel filter, emptying it, and pouring the additive directly into the filter. To the brim. It gets a good strong dose that way.

thats a good point, one for the reference book

 

[fredfloggle]

If you're going to bung fuel additive in, try first removing the fuel filter, emptying it, and pouring the additive directly into the filter. To the brim. It gets a good strong dose that way.

I'd have to disagree with this - if this is like all the othe fuel filter I have used , to empty it , then refill it would lead to possible contamination of the fuel pump - if you change the filter OK , otherwise think twice.

 

[pentax]

...problem solved

...unsteady idle depends directly from "heater booster" ...there is three options in menu: "ON" "OFF" "press EC to turn off" ...in last position it`s obvoius - idle IS unsteady if EC light is off ...when pressing EC after it (EC light goes on) - problem disapears like it never happened

...so ...is it normal with all such cars???