You have an engine we don't see here; isn't that an L-4? If so there is no "left bank" since you have only one.

In any event. you don't state the miles, but a bad O2 sensor, clogged cat or vacuum leak could also trigger the fuel trim code.

Injectors are pretty hardy, but there are connector kits for them which suggests that they may be worth replacing. So I'd suggest swapping the #1 and #2 injectors, replacing the connector on both (since you're disturbing #2) and inspecting everything for a vacuum leak while you're there.

I'd also test each of the ignition leads just to be sure.

Good luck and please do post back with the outcome; also, please click user CP and add your vehicle and location to your profile.

 

You have an engine we don't see here; isn't that an L-4? If so there is no "left bank" since you have only one.

Hi Gregs210,

I believe it's an I4. I found the exact specs after tracing my engine code with Mercedes-Benz W210 - Wikipedia, the free encyclopedia

2.0 16V K I4 163 PS (120 kW; 161 hp) 230 N·m (170 lb·ft) M111.957 E200 Kompressor

Whats a "left bank" ? I thought there's a bank 1 and bank 2. Or do you mean to say I've only got 1 bank?? So I'll never get error code of P0174?

In any event. you don't state the miles, but a bad O2 sensor, clogged cat or vacuum leak could also trigger the fuel trim code.

The car has done 138k KM. So thats like 80k miles?

For O2 sensor problems, how do I detect that? From forums it seems if it's a bad O2 sensor, it should give me a different error code on OBDII. Thats the same case with Cats also I thought?

Also, it's not a P0170 or P0173 which I believe are Fuel Trim codes. Mine is P0171 which says System too lean. I believe they are closely related but I've never got Fuel Trim error codes before.

Injectors are pretty hardy, but there are connector kits for them which suggests that they may be worth replacing. So I'd suggest swapping the #1 and #2 injectors, replacing the connector on both (since you're disturbing #2) and inspecting everything for a vacuum leak while you're there.

Ok I'll see if there's a connector kit sold in the shops. I believe this mean whenever the injectors are replaced, the connector kits must be replaced?

I'd also test each of the ignition leads just to be sure.

I don't think they come with leads. It's ignition coil guns and I swapped them around and the problem remains the same.

Good luck and please do post back with the outcome; also, please click user CP and add your vehicle and location to your profile.

[/QUOTE]
Thanks.

 

On the fuel side, replacing the fuel filter to me would be a lower cost prudent investment, as well as a can of good fuel treatment to clean the injectors over time, and a new air filter would be a 3rd prudent investment.

Please be more specific about the replacement MAF you purchased - was this sensor only or entire assembly ? Was this no-name, rebuilt, or what assurance do you have it was genuine new Bosch ?


Inquiring minds want to know..

Keep the faith !

 

Hi Fabbrisd1,

Thought there were some discussion that we should not use fuel treatment as they harm the cats?

The replacement MAF is a complete assembly. It's original Mercedes. I couldn't find the Bosch sensor locally from the parts shops. It cost me like 150USD, not as cheap as what other forummers mentioned when they purchased the sensor alone, but I thought that was just the problem so I just went ahead to buy whats available.

Before and after the change, the symptoms, occurance frequencies, were exactly the same. So I realized the new MAF had no impact.

 

Hi all,

I've been researching alot of of the related problems on this forum and other mercedes forums but I couldn't any resolution to this. Almost kinda giving up but I'm sure I'm narrowing down things alot already.

Car:
W210 Kompressor 1998cc Petrol
Year build 2001.

Here's the problem:
During daily cold start in the morning(avg temp 25degrees C), the engine will seems like misfiring. Stutters. If you rev it, you can hear it's like missing a beat and very quickly (within a minute) the stuttering disappears.

On worse scenarios, the misfiring is so bad and the CEL will be on. OBDII scanner shows P0171 - System too lean (Bank1). Very occasionally, it will also have P0301 - Cylinder 1 misfire detected. Lets say out of 5 instances of P0171, 1-2 cases will be accompanied with P0301.

I've went to a few mechanics and they suggested things like plugs, coils, which I've all changed. Plugs were initially changed to Iridium and it got worse. I threw away the plugs and bought Platinum ones and seemed better. Coils were changed with no significant differences.

From the forum research, this error P0171 is related to MAF sensor. So I replaced with a brand new one. And the problem persisted exactly with no improvement.

Another experienced Mercedes workshop said this could be due to fuel issues as well, ie fuel pump, fuel filter+accumulator. But I would assume if fuel is a problem, it would have also caused "P0174 System too lean (Bank2)." ?? But I've never had this P0174 error on Bank2. But ok some forumers also mentioned about the fuel delivery, so I proceeded with the change as well.

Now, after I've made all these parts replacement and the fault is still recurring, the workshop is suggesting I change the injectors. :surrender:

From Forum, it seems injectors for W210 are seldom faulty or clogged. Even the parts shop don't seems to have ready stock for this. They said they can order this in within days but it's not a frequently changed part (ie sensors). So I'm wondering if anyone has any idea/suggestion what I should do?

I'm just thinking of swapping the injectors (ie rotate injector 1&2 to 3&4) and see if it'll cause P0174 System too lean (Bank 2)?? But from my understanding, the injectors aren't that straight forward to be changed? Probably 1/2 a day's effort?

Or has anyone came across this problem and can link this to any other sensors issues? I'm not sure if there's a O2 sensor in each bank?
Offhand I think there's a O2 sensor for upstream and downstream.

hi kianbeng ....

about the code P0171 ...P0171 - System too lean

basically ... it was straight forward indicated ....
your engine was running with More air Less fuel ....

please check all intake pipe line connection ... like vacuum hoses , breather hoses .... etc
mostly it was loosed .... cause air leaks .... an unmeter air ...

hope this helps ,

 

Hi Gan 2660,

Yup I know it's too much air, too little fuel. But you see, the problem only occurs in the morning on cold start and it goes away quickly within a minute of warming up.

If vacuum hoses, breather hoses are leaking, wouldn't this be consistent regardless of the engine temp?

 

Also check the R170 forum, since basically the same engine is used in the SLK230. I know that on the Kompressor models there is some sort of oil separator which tends to crack and allow extra air in. Apparently a cheap part but difficult to remove due to corrosion.

 

Hi Kobus,

ok I've not checked this part yet. But my problem is only during cold start.

 

I might suggest you reseat the MAF to make usre it is seated and locked in properly - just a helpful thought.

 

Could the O2 sensor be a culprit?? These are 4 wire and as I understand have built in heaters to work correctly - maybe that part is busted and so after a minute its heated by exhaust and working properly..

Does the problem "slowly go away" or like a step function there one second, gone the next? just a thought..

 

Hi Greggster,

Which O2 sensor is this? Upstream or downstream? I remembered only 1 of the O2 sensor has a high frequency of replacement according to the shops.

 

:thumbsup: Lots of good advice here....

So here's my 2-Cents from your symptoms: When the engine is cold, it needs a little more gas so possibly check the Cold start valve, if your engine has one.

You might be able to remove the cold start valve, plug the hole, re-attach the fuel line to the valve and watch it spray gas into a clear plastic bottle. You want to see a nice spray mist, not a stream of gas... also check to see that the valve does not leak/drip after the cold start cycle is complete.

 

Hi all,

Just some updates. After replacing the fuel filter (with accumulator) and fuel pump few weeks back, I no longer get the CEL "System Too Lean - Bank 1" anymore. I had it once after the replacement within a few days but thereafter it's been quiet.

But on cold start, I'm still getting some shaky engine....I believe the root problem isn't totally resolved but it's at least much better without the CEL light coming on every few days.