n1ywb
NAXJA Forum User
- Location
- The Green Mountains
So today I broke out the old analog volt meter and hooked it up to my O2 sensor. At idle, it swings rhythmically from about 2v to 3.5v at a frequency of about 0.5hz give or take. Based on what I know this indicates that the sensor is probably operating correctly. My understanding is that the O2 sensor doesn't really measure the mixture, but rather when the voltage crosses 2.5v it indicates that the mixture is stoichiometric, and the ECU continuously tweaks the mixture so that it swings back and forth over 2.5v constantly and thus maintains something close to stoichiometry. Can anybody confirm or deny this?
Also when I ground the O2 sensor, the engine starts to run rough, which I assume indicates that I am in closed loop mode. If I was in open loop mode, then grounding the O2 sensor should have no effect, correct?
It's also worth noting that my knock sensor has been knocked off the engine block. It still seems to run in closed loop, so I guess the ECU doesn't care. According to the official Renix manual, it's not very useful anyway. It just retards like crazy whenever it detects knock, then slowly ramps up again, it's not smart enough to settle at a timing value thats just below the knock threshold, like some more advanced FI systems. Again can anybody confirm or deny this?
According to the Renix manual, only four sensors are tested at key-on for closed loop operation: MAP, coolant temp, intake temp, and TPS. The ECU tests these at key-on and will bork to open loop if it detects an open or short. I'm not sure why it leaves O2 off the list, obviously it needs that to run closed loop. It's possible it doesn't get tested at key-on, perhaps it can't be tested, at key-on it wouldn't put out a useful value anyway.
One very interesting thing in the Renix manual:
So I guess the coolant temp sender isn't even really required for closed loop, it probably just takes longer to enter closed loop if the engine is already warm.
I guess this means that problems with the other sensors (CPS, TDC) won't force closed loop although obviously that would still affect drivability by messing up injection and spark timing.
Does anybody have a table to corrolate MAP sensor resistance to barometric pressure? The Renix manual says the DRB-II tool can be used to test the MAP by displaying it's reading in millibars and comparing that to the current pressure at your location corrected to sea-level.
Also when I ground the O2 sensor, the engine starts to run rough, which I assume indicates that I am in closed loop mode. If I was in open loop mode, then grounding the O2 sensor should have no effect, correct?
It's also worth noting that my knock sensor has been knocked off the engine block. It still seems to run in closed loop, so I guess the ECU doesn't care. According to the official Renix manual, it's not very useful anyway. It just retards like crazy whenever it detects knock, then slowly ramps up again, it's not smart enough to settle at a timing value thats just below the knock threshold, like some more advanced FI systems. Again can anybody confirm or deny this?
According to the Renix manual, only four sensors are tested at key-on for closed loop operation: MAP, coolant temp, intake temp, and TPS. The ECU tests these at key-on and will bork to open loop if it detects an open or short. I'm not sure why it leaves O2 off the list, obviously it needs that to run closed loop. It's possible it doesn't get tested at key-on, perhaps it can't be tested, at key-on it wouldn't put out a useful value anyway.
One very interesting thing in the Renix manual:
Note: If the ECU does not receive input from the coolant temperature sensor, it will simulate the sensor input by defaulting to the input from the air temperature sensor and add 1/2 degree C for every 85 engine revolutions.
So I guess the coolant temp sender isn't even really required for closed loop, it probably just takes longer to enter closed loop if the engine is already warm.
I guess this means that problems with the other sensors (CPS, TDC) won't force closed loop although obviously that would still affect drivability by messing up injection and spark timing.
Does anybody have a table to corrolate MAP sensor resistance to barometric pressure? The Renix manual says the DRB-II tool can be used to test the MAP by displaying it's reading in millibars and comparing that to the current pressure at your location corrected to sea-level.