DavidM
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| posted on 1/6/13 at 10:43 PM |
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Eunos Roadster - Running Rich
My 1990 1.6 Eunos Roadster is running very rich. It has a catalytic convertor and there seems to be no facility to adjust the mixture. I have noticed
that near the cat there is a probe of some kind tied up out of the way, as if it was once connected to the exhaust but is no longer. There is no
facility to connect it to the cat or the exhaust. It is not the lambda sensor as that is near the manifold.
Does anyone have any ideas what this may be, and also any ideas why it may be running rich?
The car runs well, is low mileage and was recently given a full service.
David
Proportion is Everything
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chrism
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| posted on 1/6/13 at 11:39 PM |
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I broke a 1.6 eunos last year and dont remember any probe near the exhuast, any pictures may help to identify.
How do you know its running rich?
Possible causes for running rich could be a failing O2 sensor or Air Flow Meter, possibly also engine temperature sensor.
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A little hard work never killed anyone, but why take the risk!
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cliftyhanger
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| posted on 2/6/13 at 06:02 AM |
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the ecu thinks that the mixture is correct, so the sensors are sending incorrect info.
The lambda sensor could be duff, or a temp sensor. (ie if it thinks the engine is cold then the mixture will be richened, think choke)
Air leaks into the exhaust before the lambda will do it too (too much air means the sensor thinks the exhaust gases are lean, so richens up)
You need to find out what that sensor tied out of the way is. I wonder if it is one of those "gizmos" sold on fleabay to give extra power,
when in fact it is a resistor to replace an engine sensor which richens the mixture. Of course, if it is that and correct it, I wonder if you will
miss the "25% power increase" that was promised.
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ed1801
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| posted on 2/6/13 at 07:34 AM |
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Iirc imports had a temp sensor for the cat which would eventually fail and then light up on the dash, and it might be that. I think there is more info
on the mx5oc forum.
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ed1801
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| posted on 2/6/13 at 07:43 AM |
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Like here http://www.mx5oc.co.uk/forum/forums/p/13528/153511.aspx#153511
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DavidM
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| posted on 2/6/13 at 10:45 AM |
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quote:
Originally posted by ed1801
Like here http://www.mx5oc.co.uk/forum/forums/p/13528/153511.aspx#153511
The sensor shown in that link is the same as the sensor that is tied up under the car. Can I assume as UK cars weren't fitted with this probe
that it doesn't affect mixture?
I know the car is running rich because of the emissions test on its MOT. It read 7 and the tester said normally on a CAT car it should be about 0.5,
or on a non CAT car about 1.5.
How would I check the sensors which would affect mixture?
I don't really understand the electronics side of modern engines so any help would be great.
David
Proportion is Everything
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chrism
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| posted on 2/6/13 at 11:02 AM |
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Its weird that my 1990 1.6 eunos didnt have one, but it sounds like its just there to measure exhuast temperature.
If the cars running rich then the extra fuel can cause the cat to overheat and fail, hence why there are sometimes a temp sensor, I had a Renault
Megane a few years ago and one of the coil packs failed so unburnt fuel was going into the exhaust causing it to overheat and a light came on the dash
to say overheating cat.
removing the sensor from the exhaust wont cause the engine to run rich its just there to tell you if the engine is running rich causing the cat to
overheat and fail, so if the cars been running rich for a while and someones removed the sensor from the exhaust to get rid of the warning light it
could be that the cat has failed which I think would cause the high emissions.
When I scrapped the old cat from my eunos, they said it was only a quarter fill cat, so not a full cat which would give higher emissions anyway.
Probably as others have said it will more than likely be the O2 sensor, unless someone has been messing with the AFM, or trying one of the air temp
sensor resistors of ebay.
As for checking the sensors, Im not really sure as I cant remeber if they have a proper diagnostics port on them to show the outputs, I think because
of the age they wont. I think due to the age of the car its just a case of replacing parts to see, I not sure if the engine temp sensor also feeds the
dash temp gauge aswell as that would rule that one out, but then it may be a separate sensor.
If you could download a service manual it may give you some pointers, Ill see if I can mind the one I had on my pc and try and upload it somewhere.
https://docs.google.com/file/d/0BxnNZZ_tBs7_bXZ0NEs2VDhXZjg/edit?usp=sharing
[Edited on 2/6/13 by chrism]
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A little hard work never killed anyone, but why take the risk!
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Smoking Frog
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| posted on 2/6/13 at 11:40 AM |
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You could try this diy diagnostic http://www.mazda-madness.co.uk/2010/03/diagnostics-for-the-eunos/ it may help then again it may not.
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DavidM
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| posted on 2/6/13 at 01:29 PM |
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Thanks for your help fellas. I'll try a bit of diagnostics.
David
Proportion is Everything
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