Chris H
master of boobies
Not really sure how to title this article properly.
Anyway this article covers some more on EFI operation, what data the XRD (made by fastchip.nl) will show and what it means.
The diagnostic socket in the fusebox has a direct link to the ECU serial data can be recovered through this.
The XRD (and similar units) plug in to this socket and interpret what the ECU is doing. Theres sensor inputs and actuator outputs shown. Not everything is covered sadly.
Ok so heres some pictures, this is in the white2k9 chamade
This is the first screen, here we have injector duration in milliseconds, inlet manifold pressure in Pascals, engine coolant temperature, air inlet temperature and lambda voltage
This screen shows engine rpm, road speed, battery voltage, throttle position percentage and idle control valve percentage
This is a picture of the first screen after a cold start in the snow, it had been runnign for a few moments before this picture was taken
There are other screens showing max recorded values and theres also some acceleration data etc also included.
Ok we know what is shown, we see the pictures, but I don't know whats going on!
Well allow me to explain things then.
Lets start from the top.
Injector duration, this data is only time the injectors are opened, it doesn't tell you if they are operational, how close they are to 100% duty cycle or what they are flowing. Its only the operating duration the ECU is outputting. This figure is derived from base maps with correctional values added/subtracted for the operating conditions, e.g. starting in -20 requires more enriched mixture than that in a sunny 20 degree day.
The data in the second picture shows a duration of 2.10 ms, this means the injectors are being held open for 2 thousandths of a second. This is with a warm engine so it is operating with closed loop feedback control, this figure of 2.10 ms will vary constantly in to retain emission's compliance. If this was open loop the figure would remain constant unless change in engine load/temp occurred.
2.10 ms also tells us something else, it tells us that the engine runs batch or simultaneous if you prefer injection. This means that ALL injectors fire every revolution of the engine. If it was a sequential system then the injector duration would be in the 3 - 4 ms region.
The last picture shows a duration of 5.12 ms, more than double that of the hot idle. This is due to cold start enrichment. This basically means extra fuel injected to keep the engine running smoothly and to enable it to get up to operation temperature quicker. This figure will reduce as the engine coolant temperature increases. Cold start enrichment tends to be gone between 50 and 80 degrees (depends on manufacturer and the ecu maps).
Injector duration varies a lot, on overrun it will go to zero with an occasional cycle (some call this tau cut, basically a catalyst saver), when the engine is warm and you start it the duration will be higher for a few seconds then drop, this is to stabilise the idle and prevent stalling. When returning to idle the duration will increase (ICV activation to stabilise idle) then slowly decrease to a normal idle duration.
MAP value
MAP (manifold ABSOLUTE pressure). The absolute is critical. 0 is a total vacuum, atmospheric pressure is regarded as 1 BAR or rounding DOWN 101kPa.
Before the engine starts the MAP value should be around 100kpa, it will be lower if you live up a mountain. Weather etc alters it. But if you have a reading of 45kPa with the engine off then you have an issue with the MAP sensor or a plugged vacuum line to it. The reason for this is the inlet tract will be at atmospheric pressure.
In the second picture you will see the the reading is 34kPa, this is a good figure, it will be around this region at idle, it should hold relatively steady, if not then theres some valve sealing issues or you have big cams/got to much overlap. The figure will vary around this value depending on atmospheric conditions and what load the engine is under, the more load the more ICV control is involved thus a higher MAP value.
At WOT the value will creep up to but will not quite meet atmospheric pressure. Say at 100mph you come off the throttle then the value will go to the lowest possible as this is the situation where intake pressure drop is highest. It will drop to around 10 or so kPa.
The figure should respond quickly to any throttle changes, if not then the MAP line may be clogged with oil etc or the sensor is defective. They are however very reliable.
Coolant and Air temperature sensors
Starting from cold these sensors should be showing an identical value or be within 2/3 degrees of each other. If not one/both of them are faulty. Use common sense, if the temp outside is T-shirt weather then the coolant reading of -15 is wrong as well the +78 degrees AIT reading!
So both are the same or close enough, the coolant value will increase quicker and will be hotter than the air temp sensor.
The air temp sensor will always be hotter than the ambient temperature due to heat soak of the inlet manifold. If your sitting in traffic for ages with the fan constantly cycling then the reading of over 50 degrees is correct its not an error, it should cool down once you get moving again.
Engine operating temp should be around 86 degrees, it will cycle around this value though.
Watching the temp increasing values, they should increase in a linear fashion. A common failing is the temp climbs then reaches a certain temp and then the temp plummets or even increases, for example 34, 35, 36, -4, 39.
This is a classic faulty sensor, it needs replaced. Another common issue is the sensor plateaus, it will go to 82 degrees and despite the engine temp increasing the value will not increase, this needs replaced.
Issues arising from faulty temp senders are numerous, heres some common ones;
idle surging
hard to start
excessive fuel consumption
can't pass emission test
Lambda
The lambda/O2 sensor lives in the exhaust and measures oxygen content of the exhaust gasses. The value given here is in Volts as that's what it outputs. The operating range of the Lambda is 0.2 - 0.8 volts it can go out with these limits but generally not when closed loop is in operation.
The voltage when working correctly should vary between these values once a second. Thus averaging 0.4 ish V at stoichiometry (14.7:1).
When cold the lambda value is ignored, same during acceleration and over run. However it will still be outputting voltage.
Cold start enrichment will have the voltage staying high, it will still switch but will switch between higher values.
During heavy acceleration the voltage will again remain high.
On over run it will go low remain low and as injection kicks back in start switching again.
If at idle the cars warm and the voltage is switching slowly or its remaining high or low then your never going to get proper closed loop operation, instead the mixture will be away to pot.
If its switching slowly then the heater circuit may be faulty or it may just be clogged up, they can be cleaned, I find a blowtorch a very good way of doing this.
Same if it remains high or low, try cleaning first see what happens if its low then check for air leaks into the exhaust system before the lambda sensor if high check the CTS etc are giving the right data and that its operating in closed loop.
rpm
this is fairly simple, the engine rpm nothing to really say, it will oscillate around a bit at idle thats normal as is slight variation at constant throttle angles.
Sometimes you may watch it and see the rpm reading drop right down this means the sensor is dying. Its usually temperature dependant.
vehicle speed
vehicle road speed, again fairly straight forward. If your doing 70 and it says 0 then the speed sensor is either missing or faulty.
Voltage
This is the voltage the ecu gets, this is essentially alternator output, this will vary depending on battery charge and electrical load.
if it shows 12 or less and doesn't change the alternator isn't working.
TP
This shows throttle position as a percentage.
At closed throttle this should be between 0 and 3%, this is essential for correct operation of the idle control valve and over run fuel cut off.
Often when checking values they are above these readings or in some cases around 50 or 100%.
Check the seep of the TPS it should be free from obstruction, often its seized in the fully open position, it can jam on a screw head or just corrosion, lube the arm up and move it through its travel if its corrosion due to standing etc.
50% reading all the time usually a duff sensor, or the wires are shorting, the wires insulation breaks off on the sensors for some reason.
If its all fine but just higher than what it should be at closed throttle adjust it to 0 or 1% throttle. You should get the savings from less fuel usage and also feel the over run cut off working, in gear when you hit 1500rpm there should be a small surge this is the injectors firing again.
Idle control
This is percentage again, the more load on the engine, steering, headlights rear screen on etc the value will increase. Again this is a value output by the ECU not the actual value at the ICV, they are notorious for seizing etc so make sure they are free to operate.
That should about cover it I will do more articles on more modern live data etc, but this is about it for the limited data on these older set-ups.
Anyway this article covers some more on EFI operation, what data the XRD (made by fastchip.nl) will show and what it means.
The diagnostic socket in the fusebox has a direct link to the ECU serial data can be recovered through this.
The XRD (and similar units) plug in to this socket and interpret what the ECU is doing. Theres sensor inputs and actuator outputs shown. Not everything is covered sadly.
Ok so heres some pictures, this is in the white2k9 chamade
This is the first screen, here we have injector duration in milliseconds, inlet manifold pressure in Pascals, engine coolant temperature, air inlet temperature and lambda voltage
This screen shows engine rpm, road speed, battery voltage, throttle position percentage and idle control valve percentage
This is a picture of the first screen after a cold start in the snow, it had been runnign for a few moments before this picture was taken
There are other screens showing max recorded values and theres also some acceleration data etc also included.
Ok we know what is shown, we see the pictures, but I don't know whats going on!
Well allow me to explain things then.
Lets start from the top.
Injector duration, this data is only time the injectors are opened, it doesn't tell you if they are operational, how close they are to 100% duty cycle or what they are flowing. Its only the operating duration the ECU is outputting. This figure is derived from base maps with correctional values added/subtracted for the operating conditions, e.g. starting in -20 requires more enriched mixture than that in a sunny 20 degree day.
The data in the second picture shows a duration of 2.10 ms, this means the injectors are being held open for 2 thousandths of a second. This is with a warm engine so it is operating with closed loop feedback control, this figure of 2.10 ms will vary constantly in to retain emission's compliance. If this was open loop the figure would remain constant unless change in engine load/temp occurred.
2.10 ms also tells us something else, it tells us that the engine runs batch or simultaneous if you prefer injection. This means that ALL injectors fire every revolution of the engine. If it was a sequential system then the injector duration would be in the 3 - 4 ms region.
The last picture shows a duration of 5.12 ms, more than double that of the hot idle. This is due to cold start enrichment. This basically means extra fuel injected to keep the engine running smoothly and to enable it to get up to operation temperature quicker. This figure will reduce as the engine coolant temperature increases. Cold start enrichment tends to be gone between 50 and 80 degrees (depends on manufacturer and the ecu maps).
Injector duration varies a lot, on overrun it will go to zero with an occasional cycle (some call this tau cut, basically a catalyst saver), when the engine is warm and you start it the duration will be higher for a few seconds then drop, this is to stabilise the idle and prevent stalling. When returning to idle the duration will increase (ICV activation to stabilise idle) then slowly decrease to a normal idle duration.
MAP value
MAP (manifold ABSOLUTE pressure). The absolute is critical. 0 is a total vacuum, atmospheric pressure is regarded as 1 BAR or rounding DOWN 101kPa.
Before the engine starts the MAP value should be around 100kpa, it will be lower if you live up a mountain. Weather etc alters it. But if you have a reading of 45kPa with the engine off then you have an issue with the MAP sensor or a plugged vacuum line to it. The reason for this is the inlet tract will be at atmospheric pressure.
In the second picture you will see the the reading is 34kPa, this is a good figure, it will be around this region at idle, it should hold relatively steady, if not then theres some valve sealing issues or you have big cams/got to much overlap. The figure will vary around this value depending on atmospheric conditions and what load the engine is under, the more load the more ICV control is involved thus a higher MAP value.
At WOT the value will creep up to but will not quite meet atmospheric pressure. Say at 100mph you come off the throttle then the value will go to the lowest possible as this is the situation where intake pressure drop is highest. It will drop to around 10 or so kPa.
The figure should respond quickly to any throttle changes, if not then the MAP line may be clogged with oil etc or the sensor is defective. They are however very reliable.
Coolant and Air temperature sensors
Starting from cold these sensors should be showing an identical value or be within 2/3 degrees of each other. If not one/both of them are faulty. Use common sense, if the temp outside is T-shirt weather then the coolant reading of -15 is wrong as well the +78 degrees AIT reading!
So both are the same or close enough, the coolant value will increase quicker and will be hotter than the air temp sensor.
The air temp sensor will always be hotter than the ambient temperature due to heat soak of the inlet manifold. If your sitting in traffic for ages with the fan constantly cycling then the reading of over 50 degrees is correct its not an error, it should cool down once you get moving again.
Engine operating temp should be around 86 degrees, it will cycle around this value though.
Watching the temp increasing values, they should increase in a linear fashion. A common failing is the temp climbs then reaches a certain temp and then the temp plummets or even increases, for example 34, 35, 36, -4, 39.
This is a classic faulty sensor, it needs replaced. Another common issue is the sensor plateaus, it will go to 82 degrees and despite the engine temp increasing the value will not increase, this needs replaced.
Issues arising from faulty temp senders are numerous, heres some common ones;
idle surging
hard to start
excessive fuel consumption
can't pass emission test
Lambda
The lambda/O2 sensor lives in the exhaust and measures oxygen content of the exhaust gasses. The value given here is in Volts as that's what it outputs. The operating range of the Lambda is 0.2 - 0.8 volts it can go out with these limits but generally not when closed loop is in operation.
The voltage when working correctly should vary between these values once a second. Thus averaging 0.4 ish V at stoichiometry (14.7:1).
When cold the lambda value is ignored, same during acceleration and over run. However it will still be outputting voltage.
Cold start enrichment will have the voltage staying high, it will still switch but will switch between higher values.
During heavy acceleration the voltage will again remain high.
On over run it will go low remain low and as injection kicks back in start switching again.
If at idle the cars warm and the voltage is switching slowly or its remaining high or low then your never going to get proper closed loop operation, instead the mixture will be away to pot.
If its switching slowly then the heater circuit may be faulty or it may just be clogged up, they can be cleaned, I find a blowtorch a very good way of doing this.
Same if it remains high or low, try cleaning first see what happens if its low then check for air leaks into the exhaust system before the lambda sensor if high check the CTS etc are giving the right data and that its operating in closed loop.
rpm
this is fairly simple, the engine rpm nothing to really say, it will oscillate around a bit at idle thats normal as is slight variation at constant throttle angles.
Sometimes you may watch it and see the rpm reading drop right down this means the sensor is dying. Its usually temperature dependant.
vehicle speed
vehicle road speed, again fairly straight forward. If your doing 70 and it says 0 then the speed sensor is either missing or faulty.
Voltage
This is the voltage the ecu gets, this is essentially alternator output, this will vary depending on battery charge and electrical load.
if it shows 12 or less and doesn't change the alternator isn't working.
TP
This shows throttle position as a percentage.
At closed throttle this should be between 0 and 3%, this is essential for correct operation of the idle control valve and over run fuel cut off.
Often when checking values they are above these readings or in some cases around 50 or 100%.
Check the seep of the TPS it should be free from obstruction, often its seized in the fully open position, it can jam on a screw head or just corrosion, lube the arm up and move it through its travel if its corrosion due to standing etc.
50% reading all the time usually a duff sensor, or the wires are shorting, the wires insulation breaks off on the sensors for some reason.
If its all fine but just higher than what it should be at closed throttle adjust it to 0 or 1% throttle. You should get the savings from less fuel usage and also feel the over run cut off working, in gear when you hit 1500rpm there should be a small surge this is the injectors firing again.
Idle control
This is percentage again, the more load on the engine, steering, headlights rear screen on etc the value will increase. Again this is a value output by the ECU not the actual value at the ICV, they are notorious for seizing etc so make sure they are free to operate.
That should about cover it I will do more articles on more modern live data etc, but this is about it for the limited data on these older set-ups.
