The day has come, UPS has delivered o2 sensors to my office. Immediately I go to nearby exhaust shop during lunch break (btw this time I only replaced the upstream only as the downstream can purchased locally). I want to see if there's improvement


bosch wideband

part no

compared old vs new (not my hand )

bosch

bosch connector

original from the car

original

original

After finishing the install and starting the engine, no CEL, so it seems the install went OK. The LTFT has not coming down much yet, as its only 3km drive to the office. From quick check now the rear o2 sensor reads 0.45-0.5v during idle (previously was like 0.65v) so I hope this is some improvement? I tried to graph it on my launch it seems its steady during idle. When going in traffic it goes up and down (forgot to took a photo)

Let see on longer term. Or should I reset all adaptation values? I hope this will (finally) fix my LTFT

 

it seems the new upstream o2 sensors does not improve much on fuel trim after resetting the adaptation values I drove back home (its only 5km away) the LTFT immediately rose from 0 to 8%. Perhaps tomorrow it will get increased further.

If there is vacuum leak, when revving the engine to 2000rpm it will bring STFT to negative value for a little bit until ithe LTFT gets updated to new value (decrease) then STFT go back to 0% right? in my case nope, I rev the engine tp 2000ish rpm but the STFT stays at 0% and no change to LTFT.


rev to 2000-ish rpm


I tried to graph the rear downstream voltages, it seems one of them a little bit lazy


lazy rear o2 sensor?


downstream voltages

according to new upstream o2 sensors both bank lambda should be at 1 however the downstream said nopeeee its got different values on bank 1 and bank 2.

Possible for lazy downstream o2 sensor causing bad LTFT? both did drop to 0v when I play with the accelerator pedal.

DAMMIT ITS DRIVING ME NUTSS I'll be ordering downstream o2 sensors locally next week (starting tomorrow I'll be travelling for a few days)

 

When you are back from out of town, do emission test before replacing rear 02 sensors.
Use the car more, let the fuel trim table adapt to new front lambda sensors.
If your rear o2 is that lazy, your HC may not be at its best lowest, because CAT does remove HC and it need healthy rear o2 sensors to make CAT work properly.


When rear 02 sensors replaced, use the car some distance and do emission test again.
Make sure you do both exhaust L and R side for both emission tests....it will be a good data to have both.

This time when doing emission test ( twice ), make sure when the machine is warming up in free air, the machine oxygen sensor must read proper 20.95% +- 0.2 percent.
Take note of the emission machine Lambda value during test and at the same time use your Launch to see your front lambda sensors value too.


LTFT within +-10% is OK. Mine can be -8% and up to -12% at times, depending how I drive and it is minus sign because my setting is slightly enriched.
Remember that based on last failed emission test, your front lambda sensors were reading false rich, it was nice 0.99 of Left Bank and a mild lean 1.02 for Right Bank
while emission machine was reading a lot more lean at lambda 1.056 ( basic value ) and lambda 1.060 ( RON 93 setting ) assumed on Right Bank.



What we want to see is the new lambda sensor value on your engine must match the emission test machine , of course we assume the emission test machine lambda sensor is good and by then
you will pass the emission test.


----------------------------

Rev-ing up engine in neutral gear only changes the short term fuel trim the very second the engine rise to 2,000 RPM , very short spike up and then ST fuel trim will stabilize when that 2,000 RPM is maintained.
If you kick down fast the throttle pedal ( at neutral ) say once every 2 seconds to 4,000 RPM and do this for 15 seconds, you will see ST fuel trim increase.more.

If there is a vacuum leak ....while at idle 650 RPM, the idling fuel trim, the total of LTFT and STFT will be higher ( let say total 20% ) than when the idle is raised to 2,000 RPM , meaning the total fuel trim will decrease ( let say 10% ) at 2,000 RPM.

Actually fuel trim is to be read as total : LTFT and STFT.
If the ECM wants zero STFT, it then adjust the LTFT accordingly so that least value for STFT.

 

@S-Prihadi too lazy to wait... I just replaced the rear o2 sensors before going to do emission tests. I really want to see LTFT number improve before I took the test.


it does say original on protect.bosch.com (each o2 sensors have their own code)

bosch

original sensors (it was pretty black from carbon deposits, the mechanic wipe it off the tip)

at least the bank 1 and bank 2 got consistent graph

LTFT is not improving yet.......

LTFT is not improved yet, (I only drove for 3km after the sensors is replaced) should I reset it? or just leave it be. I might taking the car for a long italian tune up lol. Btw, LTFT does get worse if I drive the car during HOT day. On the morning drive it usually drops down to 10% or so, during the day increased again.

bonus pic...

 

Use the car more, 3KM is not even up to operating temperature yet.
So actual total fuel trim B1 is +9.7% approx and B2 at +5.4%

I am not surprised too see actual total fuel trim now, will be higher than before all 4 o2 sensors replacement.
From what we know 2+ weeks ago, before all 4 o2 sensors replaced, your engine is running lean based on emission test lambda sensor 1.06 reading, assumed right side exhaust or Bank 1.
But, the old front o2 sensors were at that time reading good normal....so we call it false rich reading.

New o2 sensors is now seeing actual lambda/AFR, ECM now can read the actual lean condition and thus must add more fuel..... the engine then get MORE positive fuel trim to make the STOICH mixture.

Some questions we need to find the answer :
01. What we need to know is, last year, what was the average fuel trims readings ?
02. Is this engine ECM programmed its fuel mix as SLIGHTLY LEAN , albeit you said it is using BASIC setting ?
03. Has the recent fuel injectors cleaning has anything to do with the leaning out of the engine ?
04. Is there any micro intake vacuum leak ?

You are heading the right direction now, which is have a proper reading o2 sensors, all 4. Without this , troubleshooting progress can't happen.

Use the car more to get the fuel trim table/memory more populated, and go for the emission test.

Yes. the Italian Tune Up is a good idea for your exhaust system.
You can keep RPM 4,000 to 5,000 if the road is not empty enough.....keep it in low gear.
Surely 1st and 2nd gear WOT pull is nicer

.

 

What I noticed now is when idling / sitting in traffic the STFT actually shows negative fuel trim. When the engine under light load (slight incline or little bit acceleration) then its positive.


STFT on idle

Actually I did saw the LTFT come down (it was 8%) then decreased to 7% when sitting on traffic. So its not a vacuum leak? When its on stop and go traffic then LTFT gets increased again.

LTFT

The number still not good tho, especially when bank 1 and bank 2 still have little bit imbalance between them. What else could be causing that? maybe the internal flaps in the intake manifold a little bit stuck somehow? but if stuck it should throw some CEL right?

EDIT: forgot to answer some of your questions

01. . Although I have the launch scanner since last year, I just began to observe the fuel trims after someone suggested to look at the fuel trim since failed emissions test
02. Now all basic value, including the ron and fuel quantity.
03. before and after injector cleaning has little effect on LTFT (its about 10-12% on my usual route)
04. vacuum leak this is I'm not sure, as I said when its idling now STFT shows negative numbers mostly. The problem is most workshop I know never even heard about smoke test/vacuum leak tester.

 

Remember, the Total of LTFT and STFT is the actual fuel quantity engine needs at that given time.
If the LTFT is always + ( positive ) , we conclude that the basic fueling of the engine is LEAN, little lean, if too lean DTC will be triggered.
Idle is when engine does not need much fuel, thus STFT starts going - ( negative ) to compensate for the extra fueling of positive LTFT.
I do not know how fast does M272 ECM will transfer the fuel trim value between STFT to LTFT or vice versa, but their total is what matters.

Let say LTFT is +7% while idle and STFT is the -5% you are seeing, therefore the actual fuel trim at that point in time is only +2% .... which is good.
When car moving, it needs more fuel and depending on how often you accelerate hard, those can be in OL ( Open Loop ) state and acceleration is always slight RICHer fuel trim,
there you see STFT as positive, which means the already at say +7% LTFT is not enough for acceleration.



Attached for your viewing, 2 driving profiles, in excel file.

Their Fuel Loop Status is shown below. 4 is Open Loop, 2 is Closed Loop.




The 92.7 minutes highway log. Remember, my car is set by ECM as SLIGHTLY ENRICHED. Under De-acceleration, engine will go super lean and it is only seen on STFT and not LTFT.


.
The negative numbers are de-acceleration.



.



If you see the Total Fuel Trim, even though that one is very dynamic ( drive dependent ), still the majority is NEGATIVE, because my fueling is as I said slightly enriched.
If you log your engine like I do for say 30 minutes rather empty highway and 10 minutes mix with city traffic jam, your Total Fuel trim majority will be POSITIVE.
So no worry.......

 

I have a smoke machine ....

This one. I use baby oil as fuel, as reccomended.

Worse come to worse if you really want to test for leak, I can help you.

 

Automotive smoke machines are relatively inexpensive on the US Amazon site, starting around $65. You'll save money over taking to a shop, even if you use it only once.

 

today I got stuck in traffic, there's big accident. stuck in traffic for 2 hours :O and of course my LTFT got worse. In traffic I got like 11% LTFT, when traffic clears up it increased to 14% :O


stuck in traffic

traffic clears up, light accelerate, park in the office, bam 14% :O


if I ran out of options, perhaps I'll try.

I was quite desperate, somehow a shop social media feed shows up on my time line, about catalytic cleaning service. I called them up and they can do mercedes.

The brand is voltronic, and their social media page they did some work on mercedes, bmw, etc. and the best part is they do home service. They are available this morning so they came to my office



they did have autel scanner, scan it to make sure there were no errors related to the engine



They also have scope camera to see the inside of the combustion chamber

before

spark plug is inspected... man last time it was cleaned was a month ago..... its dirty already (due to rich mixture ) spark plug age approx 1 year (10k kms)


carbon deposits is cleaned (again)


fluid taken out from the cylinders


Now the main thing, I never clean catalytic converter before so I guess nothing to lose




they inserted the fluid thru upstream oxygen sensors hole

and nasty thing comes out from the exhaust. SO BLACK....:O


lets see if there's improvement or not. if not improved I'm going to do smoke test....

good idea to purchase one, but this will be the last resort lol.

 

14 years of exhaust soot .....

Good sharing..... thanks

 

I hear Dawn Dish Soap will clean anything!

 

Tesna,

If I recalled correctly, you at one time did change your throttle or accelerator pedal setting ? Yes ?
You said it now offers better response.

Why don't you set it back to original/stock for the time being.
I would think if your engine fueling is set LEAN by ECM, a more aggressive throttle or accelerator pedal may make fuel trim positive higher to accommodate for it.
.

 

I like the new setting better, however I will try to return to original setting later.

But there's bigger problem, it seems the shop broke one of my new upstream o2 sensors! When they finished the job yesterday afternoon there were no engine check, so i guess its fine. However on the evening when I wanted to go home, when starting the engine the CEL turned on. They will visit again today, I hope just forgot to reconnect the cables/socket. (it was disconnected / unplugged to connect a hose to insert some liquid into the catalytic converter)





However, I'm afraid they did damage the o2 sensors when disconnecting / unmounting them from the exhaust manifold. I saw some dent on the body of the o2 sensor.....

 

Damn...... that is NOT GOOD

01. Were they using regular pliers and not special open-jaw oxygen sensor wrench / socket?
The "pinching" of the oxygen sensor body seems to be from some kind of pliers



These are oxygen sensor tools if exhaust system is still on the car, as to not damage the cable kit.


On M276 Turbo, for front and rear oxygen sensors removal, 1/2 of the exhaust system must be disconnected from the turbo and bring down to the floor.
The connector is located very high at tranny bell housing and due to turbocharger, no tools can access the front o2 sensor from the engine bay or above.
So the car must be on a lift or jack up high enough or an elevated ramp to make 1/2 exhaust system removal possible.

How did the exhaust workshop done the M272 oxygen sensors removal and installation, did they remove the 1/2 front of the exhaust system ,
or the connector is located under the tranny ?
If you can video your o2 sensor that clear and easy, that means with one of my o2 tool and a long extension , it can be removed from engine bay / from above.


-----------

02. Were the Voltronic boys ALSO were spinning out the oxygen sensor without disconnecting the cable first ? I hope not.


I am so pissed seeing Voltronic techy work this bad !!!!
Claim new sensor/s, because who knows it may go bad some months later.
See the LEFT bank o2 sensor and with a mirror too just in case the pinch mark is on the other side, any pinch mark too ?

 

@S-Prihadi well I'm not sure what they use. They did have some of the tools you shown, but due to limited space it is very difficult to do it.

The exhaust shop did have some custom made tool to do o2 sensors replacement (bit sketchy but heyy its worksss)



So I immediately go back to exhaust shop today to reinstall the original o2 sensors, upon disconnecting the damaged o2 sensors omg it even worse. Thankfully the other side seems fine.




ah well, back on original sensors, no CEL anymore. lets see how Voltronic handle this. I've sent the date of purchase, the invoice, the import duty paid, shows this is really one week old sensor. Before doing the cleaning they also scan and shown no errors related to the engine. CEL only shows up after they did the job.

 

Holy SHI-ET , its like Godzilla took a bite at that "crushed" sensor


The crushed sensor is the RIGHT Bank ( Bank 1 )
Bank 1 or RIGHT bank has steering system, that is probably why it is more difficult to work on.... if exhaust system is not at least lowered down.
The tool is a simple size 22mm socket, it only need to accommodate the cable , hence it is a partially open jaw socket.

So you need to claim 1 sensor only ...right ?
Remember Fed-Ex has a fixed local handling minimum charge, that Rp200K ish and FCP Euro shipment wont be cheaper by 50% even for a single sensor shipment to Indonesia.
So when you claim to them, tell them that or they pay back when you get the new unit/s in your hand and send them all the billing, including whatever Forex rate you pay more on the credit card.
Plus whatever charge your exhaust workshop will charge to install the new one.

Amazon can lock FX rate when we choose to pay in Rupiah, but FCP Euro can't.

 

Tesna,

I can't hep noticing your spark plug gap is a bit big, that looks like 1mm.
Mine is 0.8mm and usually MB Plugs are 0.8mm , even M271.8 EVO engine. I been buying always MB version, so it is pre-gapped already.

Right side is my s-plug of 9,000KM old , replaced in June 2021. I am doing test on my new "toy", so need to remove s-plug and I thought about your s-plugs


.





If gap is wider than spec, it will work out your COP coil more.
If COP coil is already weak ( 14 years old today ), the spark may not be powerful ( weak ignition ) and combustion won't be as good as it can be..


Sooty black is not always about RICH, but weak spark too. I do not know if the Bosch you are using is a COLD plug or normal one.



Is this kinda wet ?



The type of bosch Plug for your engine is this one :
https://www.boschsparkplugs.net/bosc...num-spark-plug

I can't see your s-plugs other than the ?????MPP33 part.

MB P/N :
A00 415 918 03 old P/N
new P/N A004-159-49-03-90
https://www.tokopedia.com/mercindo/b...hid%3D11000014

 

@S-Prihadi My spark plug looks wet because it is wet... it was drenched in chemicals so easier to clean (according to the voltronic mechanic). I noticed that too the gap is quite big, however I asked the mechanic its still fine.

Isn't not good combustion means there's misfiring? its runs fine so far. No misfiring on the scanner, no misfiring heard/felt.. dunno.

Should I re-gap it? or should I change it to MB one? Last year passed inspection on original plug tho, then not long after emission test I replace all the spark plug to bosch since it seems never changed for 13 years. The P/N of the bosch should be correct. not sure the gap.

 

Ohhh... OK, it was wet from the chemical cleaning..

Misfire is when things really go bad. Not so good combustion is a level below that.
By right that s-plug of yours is 0.8mm pre-set by Bosch, as per its spec sheet. Its tip maybe worn out only 0.05mm, the rest is gap error I think.

I replace spark plug every 4-5th year, first one at 4th year at 10,000KM ish in 2018. Later at 31,000KM in 2021. Today is 42,000KM and probably by 55,000KM or soonest 3 more years I will replace it.
My s-plugs easy can last 40,000KM even with the way I drive, but I worry more of s-plug seizing. S-Plugs are steel thread and our cylinder head is aluminum.
Its also a way to control my engine internal, as I will always send my boroscope into the chamber when I do s-plug replacement.
My fingers are also very very itchy at times.

Engine air filters are per 20,000 KM. Cabin filter HVAC, so far I have replaced twice, so total 3 units counting new one from MB back in 2014...it is always clean, but usually the activated carbon would be "saturated" already.

Best you stick with MB original s-plugs, you will replace yours no sooner per 5-6 years anyway.
BMW is very sensitive to spark plugs if not by BMW branded one, even though probably the same Bosch or NGK brand.

 

going down the wrong path by overlooking best advice is not way to success.

Master Surya NAILED IT!

Set what ever got jacked up (Pedal/ECU/?) back to stock..."NOT LATER" but as soon as you want to make progress.

Dealing with spark plugs when the ECU is handing out rich mixture is busy work... overgaping your plugs kills coils.


You've been trying to figure... why your engine fails emission testing ?

You already had the answer:
Your Bosch ECU fuel map got altered!

 

Not to make you guys jealous, but it appears I can easily access the a/f sensor and the rear sensor from the top of the engine bay on both my cars.


O2 sensors, left side, SL400


O2 sensors, right side, SL400


O2 sensor, left side, C350


O2 sensor, right side, C350

 

by later as soon I fix the CEL caused by crushed o2 sensor 😅 Since I got that sorted out by reinstalling old o2 sensors I changed it back to stock value.

Should I regap the current spark plug or just get MB one?

 

sure, regap them correctly if they are less than 30kMi. These dual platinum/iridium last for ever with hard metal on both sides.

I think spec calls for 08 gap... I undergaped my new Bosch set at 50kMi by just a hair. I did take the time to file out some imperfections. The only thing that happen after that is gap opens up and gets unreliable spark path after 50kMi so I disabled that! They would be good for 100kMi if the gap stayed consistent.

Whatever you decide to do, don't put any force at all in the center electrode - If anything should crack and fall into a cylinder while driving, this will wreck your engine in one shot. Should one plug drop to the floor: consider it cracked, don't use it.

Once you get your ECU back to stock condition you can expect more even mixtures - Hopefully your cats did not suffer heat damage from rich exhaust. ECU trim will tell you if it's lean.

 

It's very tempting now !!! When are you planning to work on those sensors?
What do you think about pigtailing them??