Dealer went through my engine and found two fuel injectors and two spark plugs that needed replacement,it helped to calm my twichty engine at idle...not perfect but better. I also complained about another problem that was not fixed and I need some help. After driving my car first thing in the morning while engine is cold (live in Florida) car runs fine until I stop at the first traffic light about 500 feet from my house. I get a hesitation when I accelerate (very mild/normal acceleration nothing strong at all) right after I stop. Problem seems to occur more if I drive the car a little faster than normal on the way to the traffic light and stop and then start again. Hesitation will go away by the time I get to the next light another 500 feet away. Your help would be most appreciated

RJC

 

Okay I guess Patrick may not have any suggestions for this so does anyone else have any suggestions or experienced anything like this?

Thanks
RJC

 

dear RJC,

As you say I do not have any suggestions. I would have if I knew more about the problem. Then again we should go all the way as I explained before: fault codes, values,...?

Your dealer replaced some injectors, but did he thoroughly clean the U-shaped gasoline distributor tube? We have never had bad injectors with these engines, but many times there was something in the U-shaped gasoline distributor tube that caused problems like rough idle, shaking, misfires,....and injectors not working properly! Most of the times it was water or just bad gasoline.
You also said that two spark plugs were bad. Did your dealer just replace those two?
Why did he think that the spark plugs were bad?
Were there misfirings in memory?

[QUOTE]Originally posted by patrick
...I have also explained that misfirings are always in memory, but you can manually change the sensitivity of that (with the Star Diagnosis laptop). If this is set to minimum sensitivity maybe some cylinders not firing so well do not become memorised? But I doubt this because USA emission laws are much more severe and the memorising of every misfiring is for these purposes...[/QUOTE

For me it seems that your problems at idle and the hesitation are one and the same.

look at what I have put between brackets!

Your dealer should make a test drive with the Star Diagnosis laptop attached to your vehicle. From the moment on that it hesitates some values must be off specs. But here again: "...needs a skilled MB technician..."!

Without having seen any values, codes or whatever, I would go for thoroughly cleaning and bleeding the U-shaped gasoline distributor tube, especially because you mentioned:

After having done that I would add an additive to remove water and clean the fuel system, but take care, there are also a lot of bad products on the market.

Are the values from the mass air flow sensor correct? If you do not want to go to your dealer, maybe you can swap it with someone you know who has the same car.

For the moment I cannot do more for you without knowing all about what your dealer has done (and measured) or having your car here with the Star Diagnosis laptop.

Is this a bit of an answer?

Patrick

 

Patrick,
I had the Dealers Team Service leader get involved with my car, here's what they did per the invoice.

SPRAY PATTERN.INJECTORS PERFORMD,T,C TEST.NO CODES PERFORM ENG AND ADJUST. CHECK FOR VACUM LEAKS AT INTAKE SEALING AREA, VACUM LINES AND AIR INTAKE--OK NO LEAKS..PREPARE AND PERFORM ME ELECTRICAL TEST, MEASURE SUPPLY VOLTAGE TO ME FROM K40/40-OK AT PINS1+2 AT CONN 2-12.3 VOLTS. MEASURE SUPPLY TO IGNITION COILS, OK AT PINS 1+3 OK AT 12.2 VOLTS AT CYLINDERS 7&8...6DW PUNCH. R/R SPARKPLUGS. INSPECT CYLINDERS WITH BORESCOPE --ALL OK..PERFORM COMPRESSION TEST 1-210,2-210,3-210,4-210,5-210,6-210,7-210,8-210. REPLACE SPARK PLUGS 2 AT CYLINDER#8. 1.82 DW PUNCH. PERFORM FUEL PRESSURE TEST=3.8 BARR. PERFORM FUEL DELIVERY TEST=1 LITRE 30 SEC. .68 DW PUNCH. LOOSEN FUEL RAIL TO GAIN ACCESS TO INJESTORS. PERFORM TEST STEP36/1=PRESSURIZE SYSTEM=NO LEAK FROM INJESTORS. TEST STEP 36/2 - CHECKINJECTOR SPRAY PATTERN. .75 DW PUNCH. REMOVE FUEL RAIL REMOVE ALL INJECTORS. CHECK FOR CONTAMINATION CLEAN FUEL RAIL INSTALL NEW INJECTORS IN CYLINDERS 7 & 8 REINSTALL OTHER INJECTORS. 1.73 DW PUNCH ROAD TEST WITH TEAM LEADER CHECK DTCS AFTER ROAD TEST..ALL OK

TEAM LEADER SAID THE TWO INJECTORS AND SPARK PLUGS WERE ALL THEY COULD FIND WRONG. I WILL MENTION THE MINIMUM SENSITIVITY FOR MISFIRES AND CHECK ON THE SETTINGS WITH HIM. I ALSO FOUND IT ODD THAT ALL CYLINDERS WERE AT 210, SHOULD THERE NOT BE ANY VARIANCE ON SOME, LIKE 209 OR 211 ETC.?

PREVIOUSLY THE MASS AIRFLOW SENSOR WAS REPLACED AND IT MADE NO CHANGE. SHORTLY AFTER THAT THE ME CONTROL UNIT WAS REPLACED AS IT WAS SENDING WRONG VALUES TO THE MASS AIRFLOW SENSOR... I'M TOLD ALL ARE REPORTING CORRECTLY NOW. THEY ALSO ADDED A PINT OF SPECIAL FUEL SYSTEM CLEANER AND IT MADE NO CHANGE.

I DO NOT KNOW IF THE U SHAPED TUBE WAS CLEANED BUT I SHALL ASK, IS THIS A SIMPLE TASK SOMETHING I CAN DO? THE TEAM LEADER SAID HE WAS GOING TO EMAIL MERCEDES BENZ FOR SOME SUGGESTIONS TO THE HESITATION I'M GETTING. THE ROUGH/TWITCHY IDLE IS STILL PRESENT AT IDLE IN PARK OR NEUTRAL WITH A/C OFF, AND AS ALWAYS WHEN IN GEAR IT'S MUCH BETTER.

PATRICK, AS I'VE ALWAYS WRITTEN I APPRECIATE YOUR INPUT BUT GETTING THE SERVICE PEOPLE TO ABIDE BY MY SUGGESTIONS IS EASIER SAID THAN DONE.

MAYBE IF YOU WOULD BE KIND ENOUGH YOU COULD COMMUNICATE TO THE TEAM LEADER VIA EMAIL FOR ME, HE IS A BRIGHT GUY AND SEEMS WILLING TO HELP ANYWAY HE CAN. IF YOU COMMUNICATE ONE ON ONE HE CAN GIVE YOU ALL THE EXACT VALUES YOU ARE LOOKING FOR. IF THIS IS OKAY WITH YOU I'LL ASK HIM AND GIVE YOU HIS EMAIL. WHAT DO YOU THINK?

AS ALWAYS, THANKS AGIAN FOR YOUR TIME AND UNDERSTANDING AND WILLINGNESS TO HELP.

RJC

 

Is this common for the US that they put that all on the invoice?

I would not have done the compression test without having first a quick look with the Star Diagnosis laptop. It has the possibility to do a sort of compression test without having to remove spark plugs and so on. If this is good it is unnecessary to do all the work, because I do not think it is a mechanical (valves, cylinder damage,...) problem. Same for the borescope check.

It is rather uncommon to replace only two spark plugs of sixteen

This is important. This may show that your dealer is familiar with possible problems with the fuel rail (and has checked this).
However I cannot know if those two injectors were replaced because of the spray pattern or because of certain values measured with the Star Diagnosis laptop.

Though I am willingly to help, this brings two major difficulties for me: first is that our Star Diagnosis laptops are in German. So it is difficult to explain what your dealer should look for. Second is that I am not English speaking. In normal language I can help myself, but when it becomes highly technical it is very difficult for me to explain certain things.

I will give it a try.
With the Star Diagnosis laptop you can see a variety of values (in German: "Istwerte"). One of them is "laufruhe". This means something as "(engine) turning quietly". Did your dealer replace the spark plugs and injectors because of these values being off specification? How are these values after replacement (very important)? If they are all the same, it will become difficult to find. But another value, that you can change, can help: "laufruhe abschaltschwelle". This is the point where the ME control unit decides to switch off the cylinder because of not turning so well. By setting this to a minimum difference, a little "twitch" will automatically get in memory. This will make it much easier to locate the problem.
Also important is "geberradadaption". This must be OK at different levels. This is how the cam sensor and crankshaft sensor are tuned in to each other (there is also a technical bulletin about humidity in the crankshaft sensor).

I would rather not communicate via E-mail because monday I start working again and I will not have much time to answer (or to spend time on the forum)
I am willingly to give you my E-mail adress at my work but I do not want it to be on the forum.
It seems that your dealer is also willingly to help. I have seen many people on the forum who encountered other dealers.

Are you sure it is the engine that hesitates? It may seem a strange question, but is not it the transmission that hesitates a little while trying to leave traffic lights when cold (engine rpm increases but car keeps standing still)? Or is the car already moving when it hesitates?

Yes. But I do not think there will be a problem with that (as I explained earlier in this post).

Patrick

 

Patrick,

Thanks for the quick reply. I will be visiting the dealer tommorow and I will first mention all the ideas you gave to me. To summarize them:

1) Engine computer sensitivity for missfires
2) Crankshaft seal sensor check for humidity and cam and crank sensor relationship.
3) U shaped fuel tube for contamination (or is this the fuel rail they cleaned?)

If after I mention all above and MBZ does not come up with a solution I may ask for you to email the team leader, but I'll save that if only absolutely nessasary. Thanks for the offer to do so! : )

When the car hesitates the engine rpms drops and car is at a stop, the funny thing is when car is cold & backing out of my garage first thing in morning no hesitation and then driving to my security gate no hesitation,crossing the street and stopping no hesitation,the hesitation follows after all I just mentioned at the first stop light and then it goes away, seems like during the transition from cold start cycle to warm (engine temp between 40 and 60 about 55).

I was told the injectors were replaced for the spray pattern.

The compression/bore scope was checked as the original dealer replaced noisy lifters (when the car was brand new 1000 miles) and had to replace one cylinder head due to a bolt they broke while dong the job!rather than tap out the bolt they gave me a brand new head. I had mentioned this to the original dealer that I seemed to notice my rough idle after all this work was done and they never found any relation, so to be sure I asked if the new dealer (I was not about to go back to the original) if they could please double check for valve leakage,vacum leaks etc. and explained the work previously done, once again no problems, but as I mentioned I found it odd all clyinders at 210, seems too perfect??

I also looked under the hood of another CLK430 and noticed that cars engine was twitchy as well just not quite as bad as mine...is this a characteristic of this engine application? I also find that if I put the A/C on it helps settle the twitch,why is this... could I have a lean miss?

Thanks Patrick!!!!!!!!!

RJC