help air/fuel problems
05-14-2002, 02:52 PM
#1
Three Wheelin'
Thread Starter
help air/fuel problems
I was playing with the car today and decided to check the voltage from the 02 sensor and discovered that it is mnot fluctuating like it is suppose to.
When I first start the car the reading is .478 volts and then it slower climbs to .650 volts.
If you rev the engine the reading stays the same.
It acts like it is stuck in closed loop mode and the computer is not looking at the O2 sensor.
If I understand correctly when you first start the car it is in closed loop until the engine warms up and then switches to open loop. Where does the computer get the signal that the engine is at temp?
Thanks, Dave Fracolli
85.5 944
unemployed bum
When I first start the car the reading is .478 volts and then it slower climbs to .650 volts.
If you rev the engine the reading stays the same.
It acts like it is stuck in closed loop mode and the computer is not looking at the O2 sensor.
If I understand correctly when you first start the car it is in closed loop until the engine warms up and then switches to open loop. Where does the computer get the signal that the engine is at temp?
Thanks, Dave Fracolli
85.5 944
unemployed bum
05-14-2002, 07:05 PM
#3
Three Wheelin'
Thread Starter
no, I spliced into the wire. I did a little more playing and found that if a disconect the water temp sensor and short the 2 wires then the computer controls like it is supposed too. the wierd thing is that water temp sensor is working?
05-14-2002, 07:19 PM
#4
Race Director
"It acts like it is stuck in closed loop mode and the computer is not looking at the O2 sensor.
If I understand correctly when you first start the car it is in closed loop until the engine warms up and then switches to open loop. Where does the computer get the signal that the engine is at temp? "
I think you have 'open loop' and 'closed loop' mixed up. The computer gets the engine-temp reading from the coolant-temp sensor. The O2-sensor won't output a correct signal until it's been warmed up to operating temperatures.
And you have to use a digital voltmeter as well. The slow response of an analog needle will dampen the dithering action.
If I understand correctly when you first start the car it is in closed loop until the engine warms up and then switches to open loop. Where does the computer get the signal that the engine is at temp? "
I think you have 'open loop' and 'closed loop' mixed up. The computer gets the engine-temp reading from the coolant-temp sensor. The O2-sensor won't output a correct signal until it's been warmed up to operating temperatures.
And you have to use a digital voltmeter as well. The slow response of an analog needle will dampen the dithering action.
05-14-2002, 07:32 PM
#5
Three Wheelin'
Thread Starter
Actually I am looking at the signal using a 100mhz o-scope. As posted if I hook up the water temp sensor then the output is basically stable rising slowly over a period of 5+ minutes. If i unplugged the water temp sensor and short the 2 wires then it controls fine. The part I don't understand is that the temp guage works when it is hooked up. Is the signal to the DME analog or digital? I guess the easist thing to do is just replace the sensor.
05-14-2002, 08:15 PM
#6
Race Director
There are actually TWO water-temperature sensors in the forward part of the head. One of them powers the gauge and the other gives a signal to the DME. Their resistance varies with temperature, but in different ranges!
The one for the dash gauge varies from 287.4-ohms@40-Celcius to 25.8-ohms@115-Celcius.
The other engine-temp sensor for the stock computers goes from 5K-ohms@0-Celcius to 200-ohms@100-Celcius.
I would test both of the sensors out in a bath of water of known temperatures to make sure they are operating within specs.
The one for the dash gauge varies from 287.4-ohms@40-Celcius to 25.8-ohms@115-Celcius.
The other engine-temp sensor for the stock computers goes from 5K-ohms@0-Celcius to 200-ohms@100-Celcius.
I would test both of the sensors out in a bath of water of known temperatures to make sure they are operating within specs.
05-14-2002, 08:49 PM
#7
Three Wheelin'
Thread Starter
Danno, thank you that was the info I was looking for! The one i disconected was the one closest to the firewall. It has 2 wires going to it. I am assuming that is the one for the guage since when I disconected the wires and shorted them I got no temp readout. Still strange though how this fixed the problem.
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05-14-2002, 08:55 PM
#8
Three Wheelin'
Thread Starter
Danno thanks, that is the information I was looking for. The sensor I unplugged was the one closest to the firewall with the 2 wires going to it. I am assuming it was for the temp guage as it did not read when I shorted the wires. Still can't figure out how it fixed the problem though.
05-15-2002, 04:45 AM
#9
Instructor
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[quote]Originally posted by Danno:
<strong>There are actually TWO water-temperature sensors in the forward part of the head. One of them powers the gauge and the other gives a signal to the DME. Their resistance varies with temperature, but in different ranges!
The one for the dash gauge varies from 287.4-ohms@40-Celcius to 25.8-ohms@115-Celcius.
The other engine-temp sensor for the stock computers goes from 5K-ohms@0-Celcius to 200-ohms@100-Celcius.
I would test both of the sensors out in a bath of water of known temperatures to make sure they are operating within specs.</strong><hr></blockquote>
Danno,
Would one of these temp sensors account for my "slightly" strange ARM1 display? The ARM1 "seems" to display the correct readings for mixture (blue on WOT, red or off when off-throttle) but will not dither at idle. Just stays rock steady in the centre. Whether the ARM is connected via the DME or directly to the O2 sensor, it's the same (which leads me to believe the O2 is working but the DME ignores it for some reason) ...
<img src="confused.gif" border="0">
<strong>There are actually TWO water-temperature sensors in the forward part of the head. One of them powers the gauge and the other gives a signal to the DME. Their resistance varies with temperature, but in different ranges!
The one for the dash gauge varies from 287.4-ohms@40-Celcius to 25.8-ohms@115-Celcius.
The other engine-temp sensor for the stock computers goes from 5K-ohms@0-Celcius to 200-ohms@100-Celcius.
I would test both of the sensors out in a bath of water of known temperatures to make sure they are operating within specs.</strong><hr></blockquote>
Danno,
Would one of these temp sensors account for my "slightly" strange ARM1 display? The ARM1 "seems" to display the correct readings for mixture (blue on WOT, red or off when off-throttle) but will not dither at idle. Just stays rock steady in the centre. Whether the ARM is connected via the DME or directly to the O2 sensor, it's the same (which leads me to believe the O2 is working but the DME ignores it for some reason) ...
<img src="confused.gif" border="0">
05-15-2002, 10:48 AM
#10
Three Wheelin'
Thread Starter
I pulled both sensors and ohmed them out. The temp sensor for the DME works fine. The Temp sensor for the guage reads greater than 20 meg ohms all the time. This still makes no sense as the temp guage works. I am going to replace it as soon as I van find one and see if that fixes the problem.
Dave
85.5 944
Dave
85.5 944