Hi
Is it possible to alter the mixture on a my93 legacy manually? Mine
has failed the emisions test (MOT) with a rich mixture, i have
checked the O2 sensor and all the associated wires to the ECU and the
only code on the CEL is an occasional 32 (despite fitting an new OE
O2 sensor!). What can I do to lower the mixture?
Any ideas much appreciated.
Manual mixture adjustment
Moderators: Helpinators, Moderators
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Josh Colombo
Manual mixture adjustment
There's really know way to adjust it manually.
What are you high on? CO or NoX. I would assume CO. Is it at idle
or high idle?
Do you get a CEL if you unplug the O2 sensor and run the car without it?
You may want to see if you get the same emissions curve without having
the O2 sensor plugged in. If so.....then it's possible the wiring
or sensor is bad.
Also.....have you tried resetting the ECU? It's worth a shot.
Josh
What are you high on? CO or NoX. I would assume CO. Is it at idle
or high idle?
Do you get a CEL if you unplug the O2 sensor and run the car without it?
You may want to see if you get the same emissions curve without having
the O2 sensor plugged in. If so.....then it's possible the wiring
or sensor is bad.
Also.....have you tried resetting the ECU? It's worth a shot.
Josh
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dpgnvq
Manual mixture adjustment
Thanks for the reply.
It failed on high idle. The only readings available on the testing
machine were lamda .93 and HC 96 (should be .97-1.3 and <200
respectivly). The landa sensor is new and i have checked it back in
the wiring to the ECU. It all checks out. I have built a LED display
for the o2 sensor and it shows that the voltage cycles between .2 -.8
V at engine speeds below about 2000 rpm but at speeds over this it
often reads .7-.8. It will sometimes read a cycling voltage when the
car is stationary as the revs are built up, sometimes not. It always
reads 0 when the throttle is backed off.
Yes I have reset the ECU a number of times and it seems to make no
difference.
I am mhaving a new back box on the exaust on monday as there is a
slight blow and will try to get it through the MOT again after this.
Regarding the CEL how soon after the sensor is unplugged should the
fault be registered on the light? I have not tried the test but will
do when i know what to expect.
Thanks again Dick
It failed on high idle. The only readings available on the testing
machine were lamda .93 and HC 96 (should be .97-1.3 and <200
respectivly). The landa sensor is new and i have checked it back in
the wiring to the ECU. It all checks out. I have built a LED display
for the o2 sensor and it shows that the voltage cycles between .2 -.8
V at engine speeds below about 2000 rpm but at speeds over this it
often reads .7-.8. It will sometimes read a cycling voltage when the
car is stationary as the revs are built up, sometimes not. It always
reads 0 when the throttle is backed off.
Yes I have reset the ECU a number of times and it seems to make no
difference.
I am mhaving a new back box on the exaust on monday as there is a
slight blow and will try to get it through the MOT again after this.
Regarding the CEL how soon after the sensor is unplugged should the
fault be registered on the light? I have not tried the test but will
do when i know what to expect.
Thanks again Dick
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Z1Auto@aol.com
Manual mixture adjustment
<PRE>What o2 sensor did you put in? Also ahve you checked for vaccum leaks
yet..sounds like a likely candidate, as the ecu is surely compensating for
some extra air it "thinks" it is seeing.
yet..sounds like a likely candidate, as the ecu is surely compensating for
some extra air it "thinks" it is seeing.
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Josh Colombo
Manual mixture adjustment
It's been a while since I've seen an emissions test.....so I'm not
exactly sure what lambda is, but it looks like you need to get it
up another 4-5 points.
As far as the unplugging the O2 sensor. When I unplug mine....I
actually don't any CEL.....which seems very odd......but it may be
that the engine is in open/closed loop mode......can never get them
straight as to which reads from the O2 to adjust air/fuel mixture.
You can try doing a search on the net....for emissions and lambda......
Also, you could try one of those can's of emissions guarantee pass
stuff. See if that helps.
Not sure if that helps.
Josh
exactly sure what lambda is, but it looks like you need to get it
up another 4-5 points.
As far as the unplugging the O2 sensor. When I unplug mine....I
actually don't any CEL.....which seems very odd......but it may be
that the engine is in open/closed loop mode......can never get them
straight as to which reads from the O2 to adjust air/fuel mixture.
You can try doing a search on the net....for emissions and lambda......
Also, you could try one of those can's of emissions guarantee pass
stuff. See if that helps.
Not sure if that helps.
Josh
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dpgnvq
Manual mixture adjustment
Hi
I used a subaru replacement and it is exactly like the one that i
removed. I have not checked for induction leaks, surely the O2 sensor
reads what is coming out so would still give a true reading even if
there was an induction leak. I will check though -where do you
suggest starting - and how, as there are no obvious leaks.
Dick
I used a subaru replacement and it is exactly like the one that i
removed. I have not checked for induction leaks, surely the O2 sensor
reads what is coming out so would still give a true reading even if
there was an induction leak. I will check though -where do you
suggest starting - and how, as there are no obvious leaks.
Dick
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Josh Colombo
Manual mixture adjustment
If you have a vacuum leak some where it will be adding more air,
the ECU will put more fuel in there....and you get your condition
of running rich.
Take a can of starting fluid or something and spray it around the
engine compartment/vacuum lines....see if the idle changes. That
may help you find your leak.
josh
the ECU will put more fuel in there....and you get your condition
of running rich.
Take a can of starting fluid or something and spray it around the
engine compartment/vacuum lines....see if the idle changes. That
may help you find your leak.
josh
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Z1Auto@aol.com
Manual mixture adjustment
By Subaru replcement do you mean an OEM subaru sensor?
As for the intake leak, it can most certainly cuase faulty O2 readings..the
ecu sees the xtra air, and compensates by giving extra fuel...probably not
the issue here, as the ecu issue sounds more likely.
As for the intake leak, it can most certainly cuase faulty O2 readings..the
ecu sees the xtra air, and compensates by giving extra fuel...probably not
the issue here, as the ecu issue sounds more likely.
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Al croxford
Manual mixture adjustment
An intake leak will not give the ECU any indication of extra air as
the air will not have passed through the MAF but will usually give
you all kinds of idle problems. Have you checked the ECU's
temperature sender on the engine ? this will also give a little
higher than usual idle. or a possible injector problem ? If you give
it a good run and kill the engine and coast to a stop the plugs will
tell a lot. (careful no power steering or brakes).
AL(CO)
the air will not have passed through the MAF but will usually give
you all kinds of idle problems. Have you checked the ECU's
temperature sender on the engine ? this will also give a little
higher than usual idle. or a possible injector problem ? If you give
it a good run and kill the engine and coast to a stop the plugs will
tell a lot. (careful no power steering or brakes).
AL(CO)
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dpgnvq
Manual mixture adjustment
Thanks for all the advice. I am still working on it.
In reply to the posts.
The sensor was a Subaru one.
I have checked and cleaned the temp sensor conections but not yet
checked the output.
I have checked for induction and exaust leaks, apart from the back
box which will be replaced tomorrow there are no leaks.
Wiring from ECU to O2 sensor checked and is fine.
ECU reset.
There are no idle problems and the car runs fine. During all driving
conditions it is a pleasure to drive. It ticks over at 800 rpm, does
not fluctuate on idle and revs right up to the red line with no
hesitation in all the lower gears. It starts well and, apart from
failing the emisions, is fine though perhaps using a bit to much
fuel.
If it does not pass the emisions tomorrow I think it is going to have
to have another ECU as there is nothing else I can think of, except,
perhaps, the CAT?
Two pieces of information I could do with -when does the ECU go into
open loop? Is it revs dependant, load dependant or just at full WOT?
The second is easy - do my93 legacy estates have a sump guard as
standard? My last subaru, a leone, did but this one never has (it
could affect the exaust temp)
Any more ideas on solving the problem will be enthusiasticaly
followed up.?
Dick
In reply to the posts.
The sensor was a Subaru one.
I have checked and cleaned the temp sensor conections but not yet
checked the output.
I have checked for induction and exaust leaks, apart from the back
box which will be replaced tomorrow there are no leaks.
Wiring from ECU to O2 sensor checked and is fine.
ECU reset.
There are no idle problems and the car runs fine. During all driving
conditions it is a pleasure to drive. It ticks over at 800 rpm, does
not fluctuate on idle and revs right up to the red line with no
hesitation in all the lower gears. It starts well and, apart from
failing the emisions, is fine though perhaps using a bit to much
fuel.
If it does not pass the emisions tomorrow I think it is going to have
to have another ECU as there is nothing else I can think of, except,
perhaps, the CAT?
Two pieces of information I could do with -when does the ECU go into
open loop? Is it revs dependant, load dependant or just at full WOT?
The second is easy - do my93 legacy estates have a sump guard as
standard? My last subaru, a leone, did but this one never has (it
could affect the exaust temp)
Any more ideas on solving the problem will be enthusiasticaly
followed up.?
Dick