How many knocksensors are there. I just was looking through my old service tickets and see that they only replaced 2 sensors. I would think that there would be 8 but I am not certain. Also I could have sworn I told them to replace them all, but it only says two replaced on the ticket.
Also I had the knocksensors done a litte longer ago than I thought....at 108K and I now have 138K...It looks like I only got 30k on these sensors.
Also they only replaced one wiring harness...is there only one?
how many knock sensors are there? q45
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Q45tech
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- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
The Consult shows if they are bad or if their resistance deviates 8% from 550,000 ohms.
Other than poor workmanship heat [either a single SEVERE overheat or just 7-10 years of normal exposure] is the only thing that destroys the plastic retaining cases.
Obviously water/coolant [from bad plenum hoses] can accelerate corrosion or failure if the KS protective housing gets cracked from a previous over heat..........kind of cumlative.
I have a special homemade emulator to quickly test [show the customer] the change in acceleration new knock sensors will create.
The problem is the SAME SHIELDED harness also transports the ecu coolant temp sensor signals. So you have to emulate that also..........trick ecu into seeing 176F and both eqivalent KS signals.
I'm not going to describe, as emulation is dangerous if the engine is not otherwise perfect..........knocking can quickly destroy pistons and incorrect temperature reading can cause mixture problems......not suitable for more than a few minutes of in traffic driving..........just enough for a WOT short test to prove the concept of replacing KS sensors.
Knock sensors are continuously monitored for function [signal] so you CAN'T just use a resistor to substitute!!!!!!!!!!!!!!!!!!!!!!!!!!!!! The ecu needs to hear some signals [not necessarily knocks].
Other than poor workmanship heat [either a single SEVERE overheat or just 7-10 years of normal exposure] is the only thing that destroys the plastic retaining cases.
Obviously water/coolant [from bad plenum hoses] can accelerate corrosion or failure if the KS protective housing gets cracked from a previous over heat..........kind of cumlative.
I have a special homemade emulator to quickly test [show the customer] the change in acceleration new knock sensors will create.
The problem is the SAME SHIELDED harness also transports the ecu coolant temp sensor signals. So you have to emulate that also..........trick ecu into seeing 176F and both eqivalent KS signals.
I'm not going to describe, as emulation is dangerous if the engine is not otherwise perfect..........knocking can quickly destroy pistons and incorrect temperature reading can cause mixture problems......not suitable for more than a few minutes of in traffic driving..........just enough for a WOT short test to prove the concept of replacing KS sensors.
Knock sensors are continuously monitored for function [signal] so you CAN'T just use a resistor to substitute!!!!!!!!!!!!!!!!!!!!!!!!!!!!! The ecu needs to hear some signals [not necessarily knocks].
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Q45tech
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- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
The attack [how fast timing is taken out] is fast, the recovery is slow.
At WOT!!!! the ecu looks at a table for ignition advance picks a number based on rpm THEN this number is modified by looking at another table: Advance vs MAF since the air could be +- 10% denser [from 70F and 29.92"] based on ambient and altitude.
THEN DECREASED by coolant temp [out of normal range] or any value in the KS accumulator..........the KS is the last thing looked at since the ecu has arrived at what should work from the other sensors.
If the no signal flag is set [failed resistance and background noise check at startup OR fails during running], a fixed amount is deducted.
The KS voltage accumulator discharges at a fixed time rate.........at 4,000 rpms there are a possible 266 knocks per second 133 from each bank, to help the ecu decide what is noise and what is really a knock, a gate is only opened [listening to each KS and FEEDING accumulator for about 10 degrees of rotation every 90 degrees alternating as the bank alternate. Additional there is an audio filter tuned to the spectrum [that knock makes at the OEM point of attachment] to help descriminate against other engine sounds]. Tapping on KS will never make it thru time gate or audio filter except by weird chance!
A REAL knock places volts in the accumulator, if only one cylinder is knocking it takes 2 rpm before the engine knocks again, so the reset time STARTS to clear [slowly discharges] the accumulator just after the 2-5 rpms.
Kind of a grade of knocking severity [say 5 step from nothing to 10 degrees] and which bank is knocking, both banks knocking is very bad and severe actions are taken to stop the knock [more than 10 degrees].
The ecu tries to decide which bank is knocking lightly and only removes timing from that bank IF RPMS are low [say below 2,500 rpm] above that rpm it doesn't have enough time to think it just pulls it out from both banks.
THE KS SYSTEM is very carefully optimized by the factory on dyno, it is an art not a science. All one can do is hope brand new sensors [not aged] will return it to near normal........lots of extra sounds develop when an engine wears over 100,000 miles.
All you can do is data log the WOT advance [many times and temperatures] and look rpm by rpm and see if anything weird is happening in the progression of the advance.
I had a problem a few years back and dropped my initial timing from 17>15...... some problems disappeared in Summer especially after I removed The K&N cone filter and went back to stock.
When I went to the better radiator, the coolant temp dropped 5F and 10F in traffic........other problems went away......cleaned egr/pcv other problems went away.
At WOT!!!! the ecu looks at a table for ignition advance picks a number based on rpm THEN this number is modified by looking at another table: Advance vs MAF since the air could be +- 10% denser [from 70F and 29.92"] based on ambient and altitude.
THEN DECREASED by coolant temp [out of normal range] or any value in the KS accumulator..........the KS is the last thing looked at since the ecu has arrived at what should work from the other sensors.
If the no signal flag is set [failed resistance and background noise check at startup OR fails during running], a fixed amount is deducted.
The KS voltage accumulator discharges at a fixed time rate.........at 4,000 rpms there are a possible 266 knocks per second 133 from each bank, to help the ecu decide what is noise and what is really a knock, a gate is only opened [listening to each KS and FEEDING accumulator for about 10 degrees of rotation every 90 degrees alternating as the bank alternate. Additional there is an audio filter tuned to the spectrum [that knock makes at the OEM point of attachment] to help descriminate against other engine sounds]. Tapping on KS will never make it thru time gate or audio filter except by weird chance!
A REAL knock places volts in the accumulator, if only one cylinder is knocking it takes 2 rpm before the engine knocks again, so the reset time STARTS to clear [slowly discharges] the accumulator just after the 2-5 rpms.
Kind of a grade of knocking severity [say 5 step from nothing to 10 degrees] and which bank is knocking, both banks knocking is very bad and severe actions are taken to stop the knock [more than 10 degrees].
The ecu tries to decide which bank is knocking lightly and only removes timing from that bank IF RPMS are low [say below 2,500 rpm] above that rpm it doesn't have enough time to think it just pulls it out from both banks.
THE KS SYSTEM is very carefully optimized by the factory on dyno, it is an art not a science. All one can do is hope brand new sensors [not aged] will return it to near normal........lots of extra sounds develop when an engine wears over 100,000 miles.
All you can do is data log the WOT advance [many times and temperatures] and look rpm by rpm and see if anything weird is happening in the progression of the advance.
I had a problem a few years back and dropped my initial timing from 17>15...... some problems disappeared in Summer especially after I removed The K&N cone filter and went back to stock.
When I went to the better radiator, the coolant temp dropped 5F and 10F in traffic........other problems went away......cleaned egr/pcv other problems went away.
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Q45tech
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- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
The CONSULT won't show how much is taken out it just REPORTS a specific amount of advance ----up to human brain to decide if this is correct for the specific circumstances AS Ignition advance can be anywhere from 13-44 degrees BTDC depending on conditions and what you are doing: idling, cruising, decel, or acel or WOT.
At idle the Consult shows 15 degrees this is NOT real it is just telling you that IF the CAS is adjusted properly with a timing light it should be 15 degrees.........the numbers it reports are referenced to 15 degrees! So a reading of 28 degrees could be real or not..........really it just means 13 degrees more than the crank is set at with CAS.
See how critical setting the intial timing is especially if you want real numbers from consult. I have seen Q set at 12>19 a 7 degree variation so max WOT could be 25-34 and still read 28!
Ideally one would install pressure sensors under spark plugs and find the timing that results in peak pressure at 16-17 degrees after top dead center.......what the factory does on the dyno, then created graphs and charts and determines the optium advance SHAPE to create this situation then installs a 2-3-4 degree back off for safety.
JWT ecu just add this "for safety amount" back to advance rates above 3,000 rpm WOT.
At idle the Consult shows 15 degrees this is NOT real it is just telling you that IF the CAS is adjusted properly with a timing light it should be 15 degrees.........the numbers it reports are referenced to 15 degrees! So a reading of 28 degrees could be real or not..........really it just means 13 degrees more than the crank is set at with CAS.
See how critical setting the intial timing is especially if you want real numbers from consult. I have seen Q set at 12>19 a 7 degree variation so max WOT could be 25-34 and still read 28!
Ideally one would install pressure sensors under spark plugs and find the timing that results in peak pressure at 16-17 degrees after top dead center.......what the factory does on the dyno, then created graphs and charts and determines the optium advance SHAPE to create this situation then installs a 2-3-4 degree back off for safety.
JWT ecu just add this "for safety amount" back to advance rates above 3,000 rpm WOT.
thansk Q45tech....I think that I understand your reponse...that even though a code 34 has not occurred on my ECU.....I could still have a knocksensor problem and I have to rely on the mechanic to determine if the amount of retardation is correct or not given the circumstances...
thanks Q45tech again for you help...and also thanks to you too as well Wes for showing my how to read the codes off my ECU.
I am going to try to find a friend with a video camera so that I can video the tachometer and upload it onto the forum so you all can see what is going on...
thanks Q45tech again for you help...and also thanks to you too as well Wes for showing my how to read the codes off my ECU.
I am going to try to find a friend with a video camera so that I can video the tachometer and upload it onto the forum so you all can see what is going on...
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Q451990
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No, if you have bad knock sensors - you should have the code. Just no "check engine" light. There's also an ohm test that you can run with a multimeter. I'll try to find it if you like.
Finding someone other than Q45Tech who will actually do data logging and look at the timing advance at different pinpoints is going to be difficult. Most techs. at the dealerships think that bad knock sensors aren't even a "real" problem. Typically the best you'll get is a simple Consult sensor test - if it says "OK" on the screen then they say it's OK.
Heath
Finding someone other than Q45Tech who will actually do data logging and look at the timing advance at different pinpoints is going to be difficult. Most techs. at the dealerships think that bad knock sensors aren't even a "real" problem. Typically the best you'll get is a simple Consult sensor test - if it says "OK" on the screen then they say it's OK.
Heath
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Q45tech
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- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
If you define OK as not throwing a code and not going into fail safe.........agreed!
However I was trying to expand the definition to included workings as brand new. That is a much harder thing to define.
An UNKNOWN situation is how does age affect the sensitivity and voltage output when a specific level of knock occurs........are they less or more sensitive or the same with age. Does their frequency response shape change.
Wierd things seem to happen BEFORE they throw their first code!
We try to get owners to change them if they have 120k [7 years] and have the plenum off for hoses/injectors] not for the money [sure we net a $150 extra for the extra work] but just because every one starts to develop tiny cracks in the plastic housing [body] by then and we hate to hear people complain about pulling the plenum multiple times in a short period.........once ever 4-5 years is enough
But then again few want to spend $500 Extra as PM, even though its a fact that they will have to pull the plenum again
However I was trying to expand the definition to included workings as brand new. That is a much harder thing to define.
An UNKNOWN situation is how does age affect the sensitivity and voltage output when a specific level of knock occurs........are they less or more sensitive or the same with age. Does their frequency response shape change.
Wierd things seem to happen BEFORE they throw their first code!
We try to get owners to change them if they have 120k [7 years] and have the plenum off for hoses/injectors] not for the money [sure we net a $150 extra for the extra work] but just because every one starts to develop tiny cracks in the plastic housing [body] by then and we hate to hear people complain about pulling the plenum multiple times in a short period.........once ever 4-5 years is enough
But then again few want to spend $500 Extra as PM, even though its a fact that they will have to pull the plenum again