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Thus the limitation of baby launch scanner......
But no worry, no aftermarket scanner can log VVT activity like Xentry in the 9 data PID format, not even US$2K Launch or Autel I am sure.
Here is the log file from Xentry VVT test in my video for data junkie to enjoy it.
I already translated the language and make modification so that Excel can create graph from it.
I also have made easy view version in WORD, called : On the road - VVT test - 3rd Sept 2023.docx
MB CAN transfers are slow, scanner has quad-core chip set: everything's limited!
The issue here is how to use our tools for our purpose.
Looks like you got things working, we've got what is necessary: vroom-vroom is user error .... not tool error
The plot we see may be suitable for our purpose:
- We don't need to measure +/- 1 degree
- We just need to confirm where to dig
- That's easier done than said:
>> compare cams. positions vs. RPM <<
Pls log or inspect single PID (1x Cam. per log) from idle to 2500Rpm in linear way up then down. Not vroom-vroom-vroom... show linear RPM sweep
Show [1x Cam + Rpm] if possible.
With these four plots we'll compare positions.
If exhaust VVT has issue it will simply show up.
Last edited by CaliBenzDriver; Oct 31, 2024 at 02:00 PM.
MB CAN transfers are slow, scanner has quad-core chip set: everything's limited!
The issue here is how to use our tools for our purpose.
Looks like you got things working, we've got what is necessary: vroom-vroom is user error .... not tool error
The plot we see may be suitable for our purpose:
- We don't need to measure +/- 1 degree
- We just need to confirm where to dig
- That's easier done than said:
>> compare cams. positions vs. RPM <<
Pls log or inspect single PID (1x Cam. per log) from idle to 2500Rpm in linear way up then down. Not vroom-vroom-vroom... show linear RPM sweep
Show [1x Cam + Rpm] if possible.
With these four plots we'll compare positions.
If exhaust VVT has issue it will simply show up.
thanks for the suggestion, however just to confirm, is this on neutral or needs to be in gear? I'll try to collect it soon.
GoOod job!
I think you have captured what may be causing your engine issue.
both banks skip synchronously
ignition angle sawtooth... is nono!
I think what's bad is the jerkiness we can observe.
What's interesting is how things go weird... synchronously meaning not randomly!
It's not just cam timing is also ignition timing does this as well.
Why ECU wants to be jerky... I'm not entirely sure.
Something is misleading the ECU to act up...
sawtooth.... is nono!
banks are synchronous
VVT actuators are working well
sawtooth...is nono!
I am going to go on a limb and guess...
this is drafty cylinders blow-by tempering with air intake sensor.
This has the exhaust camshaft table corrupted.
Guess what we get with corrupted inputs, corrupted outputs. We see unconsistentencies in exhaust positioning that are the end result of corrupted Cam. timing from inconsistent intake flow.
How to reduce crankcase blow-by is a different chapter with multiple options starting with PCV and better oiling.
pistons squirters opening up drop available pressure
This is involved with lag.
Last edited by CaliBenzDriver; Nov 1, 2024 at 03:53 AM.
Do Tesna a favor Cali, since your engine is non turbo like his and you have the baby Launch too..... share with him your Launch log under same test condition.
thank you very much for the analysis @CaliBenzDriver ! so the timing should be smooth following engine rpm then? ECU commanded that one (otherwise if deviate too much from the commanded will produce DTC right?)
The PCV system just replaced very recently, all components listed in here is replaced https://www.fcpeuro.com/products/mer...kit-oem-515810 so what else caused this? perhaps there's still vacuum leak somewhere? Or perhaps lazy o2 sensors? Currently still using the 14 year old one on the car New o2 sensor from fcpeuro should arrive within this afternoon or tomorrow. I'll redo the test once the new sensors installed.
thank you very much for the analysis @CaliBenzDriver ! so the timing should be smooth following engine rpm then? ECU commanded that one (otherwise if deviate too much from the commanded will produce DTC right?)
The PCV system just replaced very recently, all components listed in here is replaced https://www.fcpeuro.com/products/mer...kit-oem-515810 so what else caused this?
perhaps there's still vacuum leak somewhere? Or perhaps lazy o2 sensors?
Currently still using the 14 year old one on the car New o2 sensor from fcpeuro should arrive within this afternoon or tomorrow.
I'll redo the test once the new sensors installed.
I do not think old upstream lambda can cause that ECU response. They are great sensors to replace for sure without waiting for failure.
I dunno what exactly is causing that ECU response
The topic is no longer about camshaft because we see ignition timing is also involved... likely for the same reason!
I think this may be related to blow-by pressure so I would look towards MAF/MAP else find other data getting unstable vs. RPM.
Last edited by CaliBenzDriver; Nov 1, 2024 at 05:55 AM.
alright, got new o2 upstream sensors installed, so now using all 4 new oxygen sensors.
I re did the test, but only after 5km drive on new o2 sensors. but it seems all the same. now including MAF and MAP value. (MAF and MAP sensors also replaced very recently)
MAP Exhaust camshaft intake camshaft ignition angle injection time self adjustment idle speed range self adjustment upper partial range LTFT STFT MAF MAP (this should be negative right?
I am sure you can tell by the look of things there's something odd happening...
even the ECU is unable to name a fault for this condition. Manifold pressure
The intake pressure shows something ... what's responsible for this ??
The downhill/deceleration sees additional "air injection" taking place.
Why is the acceleration so unevenly weird? Acceleration jagged response then dropping
This I think is confusing the ECU Fuel Trim.
Now we can understand the ECU is adding more fuel... rich trim, specially Bk1: 12 over Bk2: 7
Intake pressure is wonky.
Here we witness a significant difference between Bk1 vs. Bk2... Left gets leaned out but Right not as much
I see this being a conseruence more than a cause, ECU response is confused... extra jagged positionings
NOTE:
-- I am begining to wonder if the 2x "air injection" valves control solenoids + diaphram + vacuum source need attention...
These 2x valves inject air in exhaust ports, right... how does that interact with intake pressure?
> PRACTICALLY:
A faulty air injection control can cause exhaust lambda to sense an artificial lean causing ECU to inject more fuel.
That means an extremely rich combustion above 14.7 ratio.
> TEST ITEMS:
These old items have a good chance to be messed up. Test functionality:
How did the air injection valves test for seal ?
How about the vacuum control solenoid?
How about vacuum pump supply ?
Last edited by CaliBenzDriver; Nov 2, 2024 at 04:37 AM.
@CaliBenzDriver perhaps those spikes caused by my bad foot on the accelerator pedal the rpm curve also corelates somehow, when the curve angle/gradient changed the spike happens. It's difficult for me to make it as smooth as possible lol
Regarding the secondary air injection, I did suspect it was leaking from the clean air to the exhaust side since master @S-Prihadi found out the vacuum did leak from the clean air side to the vacuum port of the valve (on bank 1).
However, I did several check on that valve
1. took out the valve, check for carbon build up, nope its clean. Smoke test by manual method (cigarette lol) and blowing from the clean air side, the smoke only goes to the vacuum port, not to the exhaust side.
2. when installed on the engine, disconnecting the hose to the secondary pump, then turn on the engine I did not additional exhaust sounds. Then I actuate it from launch to force it open, Immediately additional exhaust note is heard. Hence the valve sill opening on command
3. Disconnect the air supply hose from the secondary pump, turn on the engine when the engine is cold. I got the DTC of the airflow from the secondary air system is too low. No DTC when the hose is connected so the air did flow when commanded.
I guess although the membrane was leaking it still open the valve when commanded and the valve did not leak from exhaust side. I was about to delete that valve but since its not leaking on the exhaust side I leave as it is for now.
I did have problem with the vacuum pump before, it was squirting oils from the small port and the hose was broke (supplying vacuum to the intake manifold and secondary air valve) thus resulting DTC of charge movement flap malfunction. Replacing the vacuum pump and cleaning the vacuum line from oils fixed it. No DTCs related to the intake manifold anymore.
The vacuum control solenoid I guess it works since it can command the secondary air valve to open/close and the intake manifold flap is working normally.
Perhaps the MAP is working as intended? fluctuates because the flap were moving? I'm not sure. Need check on another M272 whether this behavior is normal on M272 or not.
All right, I understand you have fairly good confidence the 2x air injection controls are working as tested.
At any rate your RPM sweeps are excellent for troubleshooting purpose.
Let's explore a different route...
Intake pressure blimps crossing 1200Rpm
Ignition timings get impacted
It's not that we care what automatic ignition advance is applied - It's what happens to it that's concerning.
There's something significantly freeking out the overall ECU response.
Both banks being slightly different is also interesting to note. Mot sure why that's yet but it might be a telltale sign.
synchronously positioned Exh.cams
We already noted the disfunctional cam positioning
wicked commands
Again cam timing shows something odd is commanding this response.
intake pressure is unsettled
This is an important ECU input.
Even idling registers pressure spikes...
- Are we dealing with bad GND Ref or a mechanical issue ?
ECU seems to respond unstable but consistently.
Something has ECU and us confused....
...Something data may not be capturing.
This M272 has no EGR Valve, right?
You did cylinder compressions, right?
When dealing with unmetered air, blow-by pressure may be a concern... it bypassed MAF to directly impact MAP.
ECU is forced to hand out more fuel. (**)
Stuck leaky rings are almost granted...yes?
I'd give the engine an oiling therapy to improve piston seals. It will positively reduce unmetered blow-by.
**: We assumed the ECU was not flashed with proprietary tune to offset fuel maps.
Last edited by CaliBenzDriver; Nov 2, 2024 at 02:46 PM.
@CaliBenzDriver I hope I am right the SAI is not causing exhaust leaks thus giving false lean. Perhaps I'll try to disconnect the hose and find suitable rubber plug to block the air coming to the valve to make sure no air can escape/enter.
Yes the MAP figure is odd, accelerating / under load the MAP value is closer to zero (less vacuum) then I have negative STFT then if I accelerate long enough (or the long uphill on the highway) the LTFT gets improved. When decelerating (vacuum at highest) then STFT briefly positive
The ignition angle is similar between bank 1 and 2, if you look at the scale on the right launch somehow has different scale between bank 1 and 2.
yeah M272 should not have EGR system as far as I know.
Cylinder compression was checked on xentry by master @S-Prihadi and manually on cylinder 1 only. He said its fine. Its a little bit slower perhaps due to aging battery but its consistent on all cylinders.
Btw, can you explain more about oil therapy?
And also, ECU has been repaired before by previous owner, I think just replacing failed capacitors/component inside the ECU. The tune should be standard as far as I know.
Perhaps I should put my car in official MB dealer and pay for the diagnostics, can they found the problem?
Your car getting Master Surya treatment is worth 10 dealer visits. I seriously doubt they could achieve what he could not even with an extra ton of money.
With that being said, I am sure your M272 condition is not unique - These cars are very well built to fail the same ways.
Your engine one SAI per cylinders bank. I would concentrate on the valve with most positive LTFT. Learn how these valves fail open/closed/stuck pintle/diaphragm... then test yours.
The ignition angle shows the whole ECU is reacting to a condition... not only the camshafts acting up. The reactions are consistent.
We see a clear step in Rpm with some weirdness in pressure so that lead me to question air injection faning lambda sensor and upsetting fuel trims.
Around idle Rpm the leaks are more significant because air/fuel volumes involved are smaller than 2000.Rpm.
Again here is something significant here:
Bk1 vs. Bk2 crank Rpm
Like you say cylinders look even (good!) as far as compression BUT... we see the whole Bk2 spins faster than Bk1. This is UNUSUAL.
This suggest the whole Bk2 is getting more air than Bk1... meaning air link?
Have you tried spraying carb cleaner around seals listening for RPM changes?? (keep fire extinguisher on hand!) - Your injectors are low pressure ported by engine valves.
I am sure the solution is simple. Finding it is not. Everything is consistent with an air leak issue.
You best stay focused on related factors.
You're almost on the finish line: It's you vs the machine. Use the process of elimination to cheat positively.
+++ OILING THERAPY...
It consist in enhancing piston ring seals without burning black oil into carbon that create blow-by losses.
Reduced oil viscosity makes this worse.
Higher viscosity makes this better by cooling pistons and cleaning rings to become loose again.
Yet this is not your current priority as witnesses by "relative compression" test.
+++ 5Mn TEST: CORK/PLUG SAI VALVES
Use a bottle cork or similar to plug SAI air inlet side such that regardless of good/bad condition no air can come in. Both SAI Valves at once (Do expect related faults, no problem!) stay focussed on LTFT improving vs. no change.
Last edited by CaliBenzDriver; Nov 3, 2024 at 12:11 PM.
It's been slow week, decided to get some rest in finding the cause of the positive LTFT. I have yet to get a cork/plug, but I did measure the OD yesterday, its 30mm! lets find it
In the meantime, I decided to get xenty (it's passthru) since I already got the tactrix so I guess why not.
Finally I can see the commanded cam timing vs actual. The exhaust seems ok, but the intake there are some lags between commanded vs actual one. Should I worried? The one lags is the left one, is that bank 2?
It's been slow week, decided to get some rest in finding the cause of the positive LTFT. I have yet to get a cork/plug, but I did measure the OD yesterday, its 30mm! lets find it
In the meantime, I decided to get xenty (it's passthru) since I already got the tactrix so I guess why not.
Finally I can see the commanded cam timing vs actual. The exhaust seems ok, but the intake there are some lags between commanded vs actual one. Should I worried? The one lags is the left one, is that bank 2?
the exhaust keeps showing weird calculated response
I don't know if M272 is subject to same reluctor shift like M276 given enough rattling.
The intake being late at suc a high RPM suggest it has enough oil pressure to get positioned nearly well like the other bank.
So then how can camshaft be reported late...?
Bad sensor... would unlikely be late then
Chain skip ... how many degrees is one chain tooth?
Reluctor loose... sounds just right!
>>>> Time to go witness Cam timing marks through CPS Ports.
The exhaust seems extremely jumpy and well responsive to ECU command.... likely based on intake pressure variations.
Meaning the graph shows ok cam work on an engine made very touchy.
Intake cam delay affect how valves overlap... may impact intake pressure with exhaust pressure!!
Last edited by CaliBenzDriver; Nov 12, 2024 at 05:59 PM.
The Xentry Passthru with even genuine Tactrix Open Port 2 is too slow to do VVT logging. I think if using MB approved J2534 VCI/Dongle ( US$1.5K or more ) it will be FAST.
When your engine has RPM changes even not too fast, the VVT will play along....but the data output is too slow via the small OBD dongle we are using..
I have repeated many times about this weakness of non approved J2534 VCI/Dongle in this thread.
I replaced the spark plug with original MB because I'm curious whether this will improve my LTFT or not )
Original MB plug part no A0041594903, and it turns out made by NGK Japan with part no PLKR7A. Compared with the old one Bosch YR7MPP33 mostly the specs are the same except the resistor value. Bosch has 6K ohm resistor, whereas the NGK/original MB plug has 1K ohm resistor.
So far LTFT teeny bit improved by 1 step, now very easy to get LTFT to go to 6-7% during regular drive (previously this only possible on when ascending on a highway) and on bad traffic max value is 8.5% (previously goes to 12.5%) Cannot get to 0% yet but ah well I will leave it as it is
Below is the pictures
hmm made in japan? it turns out made by NGK PLKR7A so shiny my old plug bosch bosch YR7MPP33
Looking good, improved Long Term fuel trim using suitable and proper 0.8mm gap s-plugs.
Since acceleration need richer mix , LTFT can't be zero when fuel trim MAP is standard or lean.
As with mine being set slightly rich, I will always have LTFT negative a bit, but yes under 10% as average,
Use the car more and do report back.
Perhaps the emission test is in order now ....
However, it is a low resolution sensor when it comes to how exactly rich is a 650mV ?
Also since CAT has oxygen storage capacity, voltage swing is what we want to see from rear 02 sensor to determine its proper working or see a real stuck high voltage ( example 800 Mv )
or stuck low voltage ( example 250 mV) as "bad".
Simple explanation is : rear o2 sensor after CAT reading is not instant like front wide band sensor without a CAT.
That is why graphing the rear o2 sensor is required or watch its action when you do a few fast throttle up a few times in neutral for say 15 seconds.
We CAN'T just use 1 second view of rear o2 sensor voltage.
Google this : catalyst oxygen storage capacity
The ECM while is precise, it will do slight rich and slight poor as its adjustment method to achieve the proper Lambda 1.0 , because an engine is so dynamic while in use, hitting Lambda 1.0 all the time is not possible.
This rich-poor very mild swing is also how ECM can see CAT performance.
Here is an older test log, a car being stationary and I was monitoring oil pressure. The 02 sensors all 4 were old ones, original to the car.
ABOVE : See data points 3,800 to 4,200 which is idling only, see the Bank 2 red-sensor is lazy to swing, while the Bank 1 green-sensor is swinging above and under 450mV.
................ See data points 3,200 to 3,600 where I peg the throttle to 4,000 RPM, see how active the Bank 1 green-sensor swing above(rich) and under(lean) 450mV.
BELOW : Temperature of front Lambda sensor 1 both banks are so similar, you see only the red line , the blue is hidden under the red. Green is the Bank 1 downstream sensor.
OBD2 standard uniquely does not have Bank 2 sensor 2/downstream data PID, hence this 3 data PID only and not 4 for us a V6 or V8 or V12 twin exhaust and 4 of sensors system.
.
BELOW : Fuel Loop #4 is Open Loop at high throttle or decel. Loop #2 is Closed Loop.
While I did not play with throttle-up, from start of COLD engine to 1,200 ish data points or 4th minutes , we can see voltage swing at 800ish data point or 2.6th minutes.
Best activity of CAT ( also seen as o2 voltage swing ) is when at 500C and up, approx at 1900 ish data points.
.
I don't mean to hijack this thread, but I do enjoy your masterful contributions @S-Prihadi especially when paired with @CaliBenzDriver who is also a master.
In regards to the downstream wide bands, I have observed the lazy and often complete inactivity of bank 1 in particular (sitting at 700mV and refusing to move). After letting off throttle after 2,500 rpm blips, it will swing down to 100-200mV for a second, then back to sit at 700+.
My bank 1 spark plugs (w/ maybe 30-35k mi) look like carbon Hell. Everything including upstream 02's that would contribute to this have been addressed (besides the MAF which is working fine.) Centrifuge cover is leaking, so will be replaced along with Centrifuge (even though they about 4 1/2 yrs old, 5k mi oil changes, etc.) Fuel trims are slightly rich, but acceptable (stft always around -3 to 0 at idle and ltft always around -5ish at idle). Can I hope and pray these lazy and rich reading wide bands are contributing to my carboned plugs? They are original 15 year old 126k mi sensors. Thank you.
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