W211 E220CDI rough/hunting idle

[JohnTu]

Hi folks,
I hope you can help me with an issue I have been having for a while.
The car is a w211 FL E220 CDI om646.
When starting the car from cold, within 5-10 seconds the idle becomes rough jumping around anywhere from 600-800 rpm. Sometimes the car even dies when placed in D or R.

No codes whatsoever.
So far I did the following:
- changed fuel filter.
- cleaned and then even changed egr
- cleaned MAF
- changed fuel temp sensor (it was giving a pending code randomly)

Nothing cured the problem.
Also, the car has an intermittent “tremor” when stationary at the lights (cold & hot).

Any help is much appreciated.

 

[mersum1es]

Injector tank line (excessive) leak
Qual quantity valve.
Pressure regilator
Bad behaing EGR valve

 

[JohnTu]

Injector tank line (excessive) leak
Qual quantity valve.
Pressure regilator
Bad behaing EGR valve

No fuel leaks observed........
What’s the qual quantity valve?
Pressure regulator can be cleaned or just changed?

 

[mersum1es]

Injectors leak ALWAYS to tank. How much is the question.

Fuel quantity valve is located next to hp pump, together with pressure regulator valve it controls pressure. Pressure regulator is not anymore sold separately. But it rarely fails. FQV is far more common, by SDS you can run a test for it.

 

[horatio]

I had really bad hunting at idle on my 270 - it was the fuel pressure regulator. I bought a Bosch part for about £50, 10 mins to fit. A garage said I needed all of the injectors replaced!

At this point I would get it diagnosed at a good Indy.

 

[JohnTu]

I had really bad hunting at idle on my 270 - it was the fuel pressure regulator. I bought a Bosch part for about £50, 10 mins to fit. A garage said I needed all of the injectors replaced!

At this point I would get it diagnosed at a good Indy.

Was there any difference when hot or cold?
Mine happens only when the car is cold and turn into a "tremor" when the car is hot.

I went to an indy and no codes whatsoever...... he suggested I recondition the injectors.

 

[JohnTu]

Injectors leak ALWAYS to tank. How much is the question.

Fuel quantity valve is located next to hp pump, together with pressure regulator valve it controls pressure. Pressure regulator is not anymore sold separately. But it rarely fails. FQV is far more common, by SDS you can run a test for it.

I see. Thanks for the info.

 

[horatio]

It was a while back now but I think it got worse as the car warmed up.

These videos helped me

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[JohnTu]

Guys,
Anybody know what the MAF air flow should read at idle when the engine is cold?
Any idea where I can find the data?

 

[Khannyterraclean]

Hi mate have you solve the problem?

 

[JohnTu]

Hi mate have you solve the problem?

No, not really. I managed to make things better but it’s not 100%.
I tried to find out if there are any vacuum leaks so sprayed everywhere with carb cleaner and and WD40. I found one where the induction hose connects to the throttle body and I had to replace the o-ring there as it was broken.
Since then things improved but I can still feel the cold start rough idle and tremor but only sometimes now.
I searched everywhere for those darn readings (MAF Flow rate) but I can’t find them anywhere to see if the MAF should be changed.....

 

[Khannyterraclean]

Same here mate can't find the specified values for data streami guess xentry will solve that
However have you trief the fqv valve?

 

[JohnTu]

Same here mate can't find the specified values for data streami guess xentry will solve that
However have you trief the fqv valve?

Actually no, not yet.
I am reluctant to change the valve since most of the discussion on the web mention that if the valve is to blame, then both cold and hot erratic idle occur and mine does that mostly when cold.

 

[DSM10000]

Did your independent use Star to get the fault codes? If so then they should be able to read the live values from the MAF, cleaning the MAF is rarely successful.

There will be aberrant values somewhere that can be read and interpreted, perhaps it is time to find another MB specialist, who di you use?

 

[JohnTu]

Did your independent use Star to get the fault codes? If so then they should be able to read the live values from the MAF, cleaning the MAF is rarely successful.

There will be aberrant values somewhere that can be read and interpreted, perhaps it is time to find another MB specialist, who di you use?

He doesn't have STAR, just a good OBDII reader/computer.

Today I will perform this test that I found on a Sprinter forum (same OM646 engine):
If your Sprinter had intermittent stalling and/or erratic idle it is likely this valve failing is the culprit.
If you have these symptoms and want to test to see if the valve is the problem there is an easy test where a code reader is not necessary.
Operation: Every time the motor is started, the valve does not come into play for 30 seconds. For the first 30 seconds the computer only uses the fuel pressure solenoid at the end of the rail to maintain rail pressure.
Test: Start the vehicle and count. Are erratic idle and stalling are not present for 30 seconds and then suddenly start? Restart the motor and count again. Do the the symptoms start again right at the 30 second mark? If yes, the valve is most likely the cause. Now for the second part of the test.

Did anybody ever try this? Sounds like a simple test that could eliminate one of the possible culprits.

 

[mersum1es]

I have not confrimed what I read; Fuel quantity valve function changed at some point, it depends on model is it open or closed when no voltage.

SDS...

 

[pattiodors]

As above, find someone with the equipment to read live data ie fuel rail pressures, injector misfires etc, otherwise you will be changing parts for no reason.

 

[DSM10000]

He doesn't have STAR, just a good OBDII reader/computer.

Today I will perform this test that I found on a Sprinter forum (same OM646 engine):
If your Sprinter had intermittent stalling and/or erratic idle it is likely this valve failing is the culprit.
If you have these symptoms and want to test to see if the valve is the problem there is an easy test where a code reader is not necessary.
Operation: Every time the motor is started, the valve does not come into play for 30 seconds. For the first 30 seconds the computer only uses the fuel pressure solenoid at the end of the rail to maintain rail pressure.
Test: Start the vehicle and count. Are erratic idle and stalling are not present for 30 seconds and then suddenly start? Restart the motor and count again. Do the the symptoms start again right at the 30 second mark? If yes, the valve is most likely the cause. Now for the second part of the test.

Did anybody ever try this? Sounds like a simple test that could eliminate one of the possible culprits.

You need to find someone with Star. Anything else is a guessing game.

 

[JohnTu]

You need to find someone with Star. Anything else is a guessing game.

I know. I moved to Cyprus just before the COVID-19 crisis hit and brought the car with me.
STAR is only available in the dealership here and they charge extortionate figures even for a diagnosis. Monopoly, what can you do?

 

[DSM10000]

I know. I moved to Cyprus just before the COVID-19 crisis hit and brought the car with me.
STAR is only available in the dealership here and they charge extortionate figures even for a diagnosis. Monopoly, what can you do?

Ag, yes . I can see your problem. It may be worth you investing in an Icarsoft diagnostiics machine. Not as good as Star but can read and record live data.