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Discussion Starter · #1 · (Edited)
hello

I have been posting on this forum regarding this issue for quite a while and never have figured to fix the issue , the car in question is my brothers Volvo s40T5 2009, i will start with saying the following things are changed
-New Tcv
-New Oxygen sensor
-New Maf
-New Map
-New Volvo Spark Plugs
-New injectors both flow tested and cleaned and tested for leaks and passed
-New Fuel pressure sensor
-New Throttlebody
-New PCV and new cam seals and timing belt
-Checked all hoses and they all are tight and clamps are all good
-New check valve on the turbo which leads to the PCV
-Car runs 91Octane Fuel he has also used 95Octane to no difference in knock symptoms

I am sure i missed some , Even after changing all this the issue remains,The issue in question is the car registers during logging with vida under light load during the begining of boost upto 0.75 to 4 degress of "Ignition retardation, knocking (CA)",The net effect is boost duty cycle gets pulled by ecu and boost only hits around 3 to 6 psi and the timing gets pulled upto 4 to 8 degress,I have seen a maxiumum pull under very hard acceleration of upto 14 degress being pulled,The net result is the car feels really underpowered with the combination of very low boost (4 psi average) and ignition advance being pulled in the range of 4 to 8 degress on the onset
From logging with vida "Ignition retardation, knocking (CA)" always registers 4 to 8 degress any time the throttle is depressed and on the onset of boost

I have tried the following after researching this a lot and reading through vida

1)Checked the knock sensors resistance both of them test out at 4.8 to 5.2 mohms consistently together, and this is according to vida specs which says they should be above 1 mohm
2)I checked continuity of the 4 pin connector that goes to the ecu connector and all the 4 pins have continuity to the ecu connector , as i read these sensors are wired directly to ecu
3)I removed the knock sensor connector from the wiring harness left it unplugged and did a test drive with vida logging the "Ignition retardation, knocking (CA)"parameter.It consistently read 12 degress retard on application of throttle,Note with the knock sensor removed it was just 0 and 12,There are no in between values as observed earlier when the knock sensor was plugged and torqued to the block(4 to 6 degress to 14 degrees).This obviously is the substitute value of 12 degree retard being used by the ecu as failsafe since it can't detect the knock sensor.
4) I removed both knock sensors from the block and grounded the wires to the block and ziptied them to a nearby hose, and did a test drive with vida,Vida showed "Ignition retardation, knocking (CA)" hitting 12 degress on application of throttle,There are no in between values just 0 when off throttle and 12 degrees as soon as you get on the throttle,This seems very similar to removing the knock sensor from the wiring harness connector which makes the ecu use the substitute value of full retard 12 degrees,This is very peculiar as the knock sensor is connected and grounded to the ecu yet the ecu will still use the substitute full retard value,I can only assume the drastic change in tone received by the knock sensor makes the ecu go to full 12 degree retard
5)I have also removed the entire accessory belt from the harmonic balancer pulley to the Ac compressor and alternator,To rule out any sound or magnetic interference the alternator or the auxilary tensioner pulley are introducing that could be perceived as knock,Vida still found the same level of ignition retard as normal driving
6)The fuel trims are largely negative indicating a rich condition and the STFT goes periodically to -8 when on throttle,The LTFT is around -4.8,I have logged the lamba equivalance ratio which is basically the ratio of AFR to the stoich of the fuel and found the oxygen sensor (brand new) was functioning correcrly.I did notice under heavy engine breaking (let off throttle in highway cruise) the front oyxgen sensor goes to 16 LAMBDA , this kinda makes sense , but i find it still unusual as 16 is indeed the limit for max lean and just wanted to confirm if everyone sees the same.
7)I don't have an explanation why the fuel trims are negative,I can only assume this might be because of the ignition being retarded causing the oxygen sensor to see a lot of fuel

The engine sounds absolutely fine,no issues with idle and no codes stored of any kind,just the damm lack of power due to the low boost and retarded ignition timing and i can't even notice any sounds of detonation or knocking listening to the engine across its rev range which makes me suspects its some sort of false knock,but I have tried everything that makes sense to me and it has all tested fine or inconclusive

I have also today taken out spark plugs and taken pictures of the cylinder with a boreoscope, the finding are Cylinder 2 does have more carbon that the rest of the cylinders,but i don't think its enough to cause issues of detonation and i do see some faint brown powder(rust?) on cylinder 1 and 5 , i am attaching the pictures of these cylinder below

CYLINDER NUMBER 1 (RUST POWDER??)



CYLINDER NUMBER 2 (MOST CARBON FROM ALL CYLINDERS)




CYLINDER NUMBER 3 (LIGHT CARBON)




CYLINDER 4 (LIGHT CARBON)


CYLINDER NUMBER 5 (LIGHT CARBON AND RUSTPOWEDER??)



If anyone has any idea on how to proceed kindly chime in,Please save repeating and wasting time suggesting mundane things as i have been quite thorough with this engine,I have tried the most obvious things which relates to sensor resistance and wiring and verified there is no knocking or ticking sound from the engine,The engine sounds very healthy and revs and falls as it should,There are no idle issues,no stuttering,no nothing,also this engine has been maintained very well by my brother,He does 6k km oil changes with an engine flush every time, it has never been abused it runs and sound very good,The engine has around 170k km on it,which isn't a lot and most highway driving

thank you for your time
 

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I can see why it knocks! Carbon is a great source of preignition.

Have you checked the injectors, especially in the fouled cylinders? How about the Fuel Pressure Sensor?
 

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Discussion Starter · #3 · (Edited)
I can see why it knocks! Carbon is a great source of preignition.

Have you checked the injectors, especially in the fouled cylinders? How about the Fuel Pressure Sensor?
Hello

Firstly i do not believe this is preignition but rather detonation,these are two seperate events,Preignition would not result in the engine idling and reving with no issues across the entire rev range

Injectors and FPS sensors are what i have forgotten to list,The car has a brand new Fuel pressure sensor and all injectors have been professionally flow tested,cleaned and leak tested and passed
I will update the first post,Do you think this is enough carbon to cause detonation?.I have seen cylinders looking worse in other cars that run with no issues

Thank you
 

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The only time I've seen worse carbon buildup which was on my harley, an NA 8.5:1 air cooled engine that never hard the carb tuned from factory in it's life, and was run that way for the first 20 years of it's life, and it did not retard timing and did not ping or knock on 91+ in 100*F weather. Given that these motors are what? 10 or 10.5:1 on boost? I agree with tmtalpey - carbon is your source of issue.

#1 looks absolutely ideal for it's age. That chunk on #2 is very odd - almost like some oil ring issues I see on harleys but is definitely causing you some headache as it's a small patch that looks super thick absorbing a LOT of heat. #4 is absolutely covered, which is again, bad, and could even be modifying your compression ratio a bit.

Some people say our ECM performs calculations regarding expected torque input and we don't have knock sensors. I have never dug into the issue either way, but good to know they're real at least and I wasn't full of doodoo in remembering what I read a while ago, assuming you are also not full of doodoo in your testing of them noted above.

I agree with TMTALPEY. Given how you're only having 4-8* of timing, instead of all 20-30* at high RPM's on the stock tune, and it doesn't have a lot of power, it sounds like it's pulling timing back like a low octane mix that's predetonating (like putting 85 in the tank here and it runs much smaller advance, i.e. 4-8* total. I have seen up to 50* of advance but normally 30-40* during engine braking on the highway). You're running the entire RPM range and all conditions retarded it sounds like the low-octane map in the ECM.

I'd start a weekendly soak of those piston crowns in seafoam, crank and blow it out the spark plug holes sunday night and drive it M-F and then start it the soak again Friday night, for the next 2 months, maybe 2 or 3 gal of E85 in the 91 mixture to check for retarded timing based on knocking - if the higher octane+cooler burning mix works, you've found your issue, additional ethanol fuel (2-3gal of e85 is the upper limit on a stock tune to not trigger a CEL) will help clean the deposits as well.

Hello

Firstly i do not believe this is preignition but rather detonation,these are two seperate events,Preignition would not result in the engine idling and reving with no issues across the entire rev range

Injectors and FPS sensors are what i have forgotten to list,The car has a brand new Fuel pressure sensor and all injectors have been professionally flow tested,cleaned and leak tested and passed
I will update the first post,Do you think this is enough carbon to cause detonation?.I have seen cylinders looking worse in other cars that run with no issues

Thank you
Also detonation AND preignition would cause timing and boost to be pulled by the ECM as it picks it up, reverting to the low octane map, acting like you put 85/87 in there, and reducing heat from advancing timing, causing less detonation and preignition issues. I can say I put 85 in there for a few weeks to see how it behaved and it handled it just fine, but was very low on power. Engine idled fine and I had no isssues - but I had to have some misfires and knock codes set when I tried to put my foot down to get it going before it switched to the low octane map and I had no further issues after it pulled timing. It would make sense your computer thinks you put in low octane fuel because of the hotspots causing ignition outside of planned times and pulls timing+boost as far as it can.
 

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Firstly i do not believe this is preignition but rather detonation,these are two seperate events,
Ok, fine, but I still say it's the carbon. You need to get to the root of why that extreme buildup is occurring. These engines pretty much never look like that in normal use. Quite the opposite.
 

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Some people say our ECM performs calculations regarding expected torque input and we don't have knock sensors.
Uh, some people are incorrect. There are two piezoelectric knock sensors, at the front of the block at cylinders 2 and 4. They are quite reliable, and are definitely used by the ECM to manage knock. In response, it will pull timing and richen the mixture, among other things.
 

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Discussion Starter · #7 ·
Ok, fine, but I still say it's the carbon. You need to get to the root of why that extreme buildup is occurring. These engines pretty much never look like that in normal use. Quite the opposite.
The only time I've seen worse carbon buildup which was on my harley, an NA 8.5:1 air cooled engine that never hard the carb tuned from factory in it's life, and was run that way for the first 20 years of it's life, and it did not retard timing and did not ping or knock on 91+ in 100*F weather. Given that these motors are what? 10 or 10.5:1 on boost? I agree with tmtalpey - carbon is your source of issue.

#1 looks absolutely ideal for it's age. That chunk on #2 is very odd - almost like some oil ring issues I see on harleys but is definitely causing you some headache as it's a small patch that looks super thick absorbing a LOT of heat. #4 is absolutely covered, which is again, bad, and could even be modifying your compression ratio a bit.

Some people say our ECM performs calculations regarding expected torque input and we don't have knock sensors. I have never dug into the issue either way, but good to know they're real at least and I wasn't full of doodoo in remembering what I read a while ago, assuming you are also not full of doodoo in your testing of them noted above.

I agree with TMTALPEY. Given how you're only having 4-8* of timing, instead of all 20-30* at high RPM's on the stock tune, and it doesn't have a lot of power, it sounds like it's pulling timing back like a low octane mix that's predetonating (like putting 85 in the tank here and it runs much smaller advance, i.e. 4-8* total. I have seen up to 50* of advance but normally 30-40* during engine braking on the highway). You're running the entire RPM range and all conditions retarded it sounds like the low-octane map in the ECM.

I'd start a weekendly soak of those piston crowns in seafoam, crank and blow it out the spark plug holes sunday night and drive it M-F and then start it the soak again Friday night, for the next 2 months, maybe 2 or 3 gal of E85 in the 91 mixture to check for retarded timing based on knocking - if the higher octane+cooler burning mix works, you've found your issue, additional ethanol fuel (2-3gal of e85 is the upper limit on a stock tune to not trigger a CEL) will help clean the deposits as well.

Also detonation AND preignition would cause timing and boost to be pulled by the ECM as it picks it up, reverting to the low octane map, acting like you put 85/87 in there, and reducing heat from advancing timing, causing less detonation and preignition issues. I can say I put 85 in there for a few weeks to see how it behaved and it handled it just fine, but was very low on power. Engine idled fine and I had no isssues - but I had to have some misfires and knock codes set when I tried to put my foot down to get it going before it switched to the low octane map and I had no further issues after it pulled timing. It would make sense your computer thinks you put in low octane fuel because of the hotspots causing ignition outside of planned times and pulls timing+boost as far as it can.
There is too much sense about what is being said about the carbon on cylinder 2 to ignore, however i should also add that my brother did run a full tank of 98 octane fuel to see if it did anything for engine power,there was no difference,I would assume there was no need to reset the ecu by disconnecting battery as the knock control on these Volvo cars are the ones where it always tries to run maximum ignition advance and pulls back only on detonation, so if it was real detonation,there would be a noticeable change in perceived power running 98 octane ,he reported the same low boost and retarded ignition for the entire tank of 98 fuel.This is what led me to believe it was some sort of False knock on this engine

However like i said everything tested inconclusive and there is good sense in attempting to remove carbon from the piston crowns to rule this out completely,though doing this properly would involve pulling the cylinder head to clean each piston crown and then resealing the valve cover and replacing all the headbolts, which is a lot of work and lot of money in parts for all new headbolts and the sealant for Valvecover seal. It makes more sense to attempt the piston soak method as suggested by aveneger for a long duration and pulling it all away with a fluid extractor,I think i will soak each cylinder with "Marvel Myster oil" as this is more cheaper than seafoam with similar or better result from research, for a day and then keep removing it with a fluid extractor multiple times , my concern are obviously with carbon getting stuck within rings or carbon scoring the cylinder

As for the root cause of the cylinder 2 carbon,I have no idea,the car has been running with this retarded ignition and low boost for more than 2 years now , so i don't know if this has caused this, i will report back after getting the oil and attempting the piston soak,will post back on this thread with pictures after its done

thank you for your time
 

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Pulling the head sure doesn't seem necessary, agreed. Mystery Oil should get under that carbon and help it pop off. Maybe a good strong shot of compressed air through a long blowpipe would help too.

You say the plugs were changed, was that with Volvo OEM? That would be the most reliable choice, when getting to the bottom of this.
 

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Discussion Starter · #9 ·
Pulling the head sure doesn't seem necessary, agreed. Mystery Oil should get under that carbon and help it pop off. Maybe a good strong shot of compressed air through a long blowpipe would help too.

You say the plugs were changed, was that with Volvo OEM? That would be the most reliable choice, when getting to the bottom of this.
hello

Yes the plugs where the Volvo genuine ones , they always where swapped with Volvo part number plugs, i will followup with pictures of the bore after i do the piston soak, do you think there will be an issue with the carbon that gets broken down and possibly scoring the cylinder? or just getting stuck in the rings ?, i thought i would let it soak for a day and then break some of the carbon up with a long ended pick to keep scratching the piston crown to dislodge and break down the rest of the buildup

thank you for your time
 

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I don't think carbon will scratch or score the bores. Tape a hunk of tubing to a shopvac and stuff it down the plug holes anyway!
 

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I don't think carbon will scratch or score the bores. Tape a hunk of tubing to a shopvac and stuff it down the plug holes anyway!
+1 to this. Large enough pieces can score the bores and get stuck in the rings, but it takes a hunk of it to do the job. Given that the pistons are bowl shaped with a ridge all the way around, just be patient and careful and vacuum out the top and you should be good to go.
 

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Discussion Starter · #12 ·
brother did the piston soak with sea foam and pulled the excess fluid with an extractor , and he also ran a can of sea foam through the intake,still no difference,there is still ignition retard due to knock and loss of power in the mid and low end of the power band

still stumped on what this could be, the biggest issue is how to pin it down from false knock
 
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