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Discussion Starter #1 (Edited)
Affects on Emission

Before I purchase anything I wanted to ask about the following:

Intake elbow crack (leaking air post VAF)
Oxygen Sensors Codes
-23 RHO2S inactivation error
-24 RHO2S inversion error

I wanted to know what affects fixing the two will have on emission.

First Emission Test results:
Test | Limit | My Car's Result

HC ppm | 64 | 116
CO% | 0.35 | 0.54
NO ppm | 485 | 1325

Several mechanics mentioned oxygen sensors, then I read the codes and saw 23,24. I'm going right now to reset codes and read them again.

What affect will replacing the oxygen sensor have?
Is there 4 Oxygen sensors altogether?
What will a miss read air intake flow change in emissions?

What does the inversion code mean (24)?

Optional: Will Cat replacement be necessary?

Foot Notes:
Detail on codes and reading them: 1993-1995 Engine Controller Malfunction Codes
Full eTest Results for my Car (camera Fail, blame eTesting!!): http://tourneycpm.mrlazyinc.com/files/users/themafia/Images/Cars/Mazda Mx-6/1st_etest.JPG
 

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Resetting the codes won't change/fix anything. The effect from changing them- your car will pass emissions.
As far as I know, any of the V6 MX-6's only have two sensors. One on each exhaust manifold. Both codes are from your RHO2 sensor- The rear sensor. Replace this and chances are it'll fix everything. It's not required... but but chances are... unless you do replace the LHO2- front side one as well... It's bound to malfunction soon as well.

This is from the malfunction codes: 1993-1995 Engine Controller Malfunction Codes
"Inactivation errors 15 (left) & 23 (right) indicate the sensor never "woke up" from cold. Cold sensors produce little or no output voltage. Once the engine RPM exceeds 1500RPM, the PCME expects to see the voltage on the sensor(s) go above 500mV within 100 seconds. If it does not, the inactivation code gets set.

Inversion errors 17 (left) and 24 (right) occur when the sensor stops responding to the PCMEs adjustments to the A/F ratio. Inversion refers to the sensor swinging back and forth (or inverting) across 500mV as the PCME alternately makes the A/F ratio slightly richer or slightly leaner. If the sensor does not mirror theses changes, the PCME will set the inversion code."

Cat converter replacement isn't necessary. And the cracked elbow won't have anything to do with the O2 sensors either. All this will do is let 'un-metered' air into the system, which makes the fuel mix weird and idle funny.
 

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Discussion Starter #4
I reset the codes just to make sure I have fresh codes to work with.

I pulled the negative cable, held the brake for 20 seconds. Then pumped it 5 times. I did this because I'm not sure which of the two resets the codes.

After doing this, I tested for codes, and I got 41 repeatedly ...im not sure if that is supposed to be happening.

To make sure, I went for a heavy run, through all the rpm's all the gears, pushed it as much as i could on the city streets.

I tested again, and the same thing. 41 repeated. I do not have an oxygen sensor code anymore.

Have I done enough to generate any codes??
Am I reading them wrong?
Should I do another etest to see where the car has gone since the last time I did it?

Notes for Dewzer:
The elbow wasnt related to the oxygen sensor, I mazda mechanic suggested I patch it up before running any test, got one from a wrecker, and tossed it on.
The car idles nice now!! :D Drives solid too.
 

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Hmm... so apparently it wasn't your O2 sensors. Pushing it like that should be enough... if there were any other codes you would have seen them by now.
41 is easy. VRIS #1 control solenoid. It's the one closest to the passenger side. Be sure it's got good connection. You can check the resistance across the terminals... etc... I usually pull mine from junk yards... Mazda wants an arm and a leg...


Glad to hear the elbow thing worked out and helped. :)
 

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Discussion Starter #6
Well im going to get the emission tomorrow to see what difference there is....and someone mentioned the vris: 'someone unplugged your vris...?' didnt know at the time what it was.

My car feels a lot different after the safety was done at G&R Auto here in town. shit sounds different, feels just slightly diff.....and they are parts of the car that were not touched. I have to drive it a bit more to really dig into it.

I also feel like i need more power in the 1000 - 4000 area. First gear seems to have a very high or low ratio...resulting in much more rev. over acceleration. Second is good though, cant get past third in city at %80 - max throttle.
 

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Discussion Starter #7
Should I be worried that the code is gone? is the computer that good that it can sense the sensors working properly now and guarantee it?
 

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your symptoms sound like a bad vris solenoid (or an unplugged one)

As to the o2 codes they're volatile. If you cleared your codes and the sensors are only starting to go bad it may take a bit of time for the ecu to realize somethings not right with them. I had a bad o2 sensor that would only throw a code once a week. Still killed gas millage and made it fail emissions.
 

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you wont know till you get the car through it's drive cycles. Pushing it wont have any effect on this, driving at inconsistent speeds and some 60 mph coast the 50 mph coast then 40 mph coast will help speed this process up. If you take it to a shop that has a modis they will be able to determine witch O2 sensor is failing. If it had a code for O2 there is truly a problem. the reason you failed emissions for this is because fuel is trimmed based on what the sensor reads.
 

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Discussion Starter #11
you wont know till you get the car through it's drive cycles. Pushing it wont have any effect on this, driving at inconsistent speeds and some 60 mph coast the 50 mph coast then 40 mph coast will help speed this process up. If you take it to a shop that has a modis they will be able to determine witch O2 sensor is failing. If it had a code for O2 there is truly a problem. the reason you failed emissions for this is because fuel is trimmed based on what the sensor reads.
Whats a modis?
 

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Discussion Starter #12 (Edited)
Update:

-Codes cleared (O2 code gone, VRIS #1)
-VRIS #1 replaced and working (sweet, i can feel the super charge :)
-Etest done again just to make sure(same results):

Test | Limit | My Car's Result
HC ppm | 64 | 109
CO% | 0.35 | 0.49
NO ppm | 485 | 1387

-Catalytic Converter replaced (17" after market, recommended make for passing etest by mech)
-Ran the car in 4th 80-100km for > 10 min
-eTest redone & Pass amazingly(side note: 674 idle RPM's):

Test | Limit | My Car's Result
HC ppm | 64 | 51
CO% | 0.35 | 0.04
NO ppm | 485 | 140

Whats left:
HC ppm's still seem high, what are HC's (hydro carbons? where from?)?
 

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if you fail emissions, i've heard the first step is to replace the catalytic converter, and
let it burn in. if that doesn't make it pass, then i've heard next step is to clean/replace
the egr valve. and if it still doesn't pass, then replace the O2 sensors. Most mx6 have
2 sensors, later models have 4.
 

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Discussion Starter #14
if you fail emissions, i've heard the first step is to replace the catalytic converter, and
let it burn in. if that doesn't make it pass, then i've heard next step is to clean/replace
the egr valve. and if it still doesn't pass, then replace the O2 sensors. Most mx6 have
2 sensors, later models have 4.
Which of the 3 things you mentioned have the greatest impact on HC emissions?
 

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If you've already replaced the cat then all thats left is the O2 sensors and clean/replace EGR. EGR is a little tricky to get to... I've gotta clean mine, this weekend prolly...
O2 sensors aren't too bad to replace. If I remember right... both were cheaper to replace than the cat...
 

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hc are lowered by the catalytic by being burned up...more are formed if your motor is running rich and there is a lot of unburnt fuel making its way out the exhaust

i'm actually really pleasantly surprised about how much your NOx dropped with just a replacement of the cat. NOx is governed mostly by the EGR valve...i think i can get my mx6 to pass now ...maybe

edit - please post make of cat!!
 

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NOx is cleaned by the "filter" cat. EGR simply returns some of the gas not liquid to the engine to reuse. cats can be burned up more quickly if the O2 sensor has failed allowing fuel to be dumped into the exhaust creating a higher temp then the cat is to be operated at. If the EGR is not opening then the small amount of gas is cleaned by the converter as long as it's in good shape.
 

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Intake elbow crack (leaking air post VAF)
Oxygen Sensors Codes
-23 RHO2S inactivation error
-24 RHO2S inversion error
Did you ever change that intake elbow? I could see a slight amount of unmetered air potentially causing an O2 code which didn't return immediately.
 

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Discussion Starter #19
hc are lowered by the catalytic by being burned up...more are formed if your motor is running rich and there is a lot of unburnt fuel making its way out the exhaust

i'm actually really pleasantly surprised about how much your NOx dropped with just a replacement of the cat. NOx is governed mostly by the EGR valve...i think i can get my mx6 to pass now ...maybe

edit - please post make of cat!!
I never saw the make of the cat, but it was from Napa Auto Parts.
My mechanic recommended over a similar one from APC Auto Centers. As that one had really bad etesting.

Called my mech. he said its a "Maramount Cherrybomb"
 

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Discussion Starter #20
Did you ever change that intake elbow? I could see a slight amount of unmetered air potentially causing an O2 code which didn't return immediately.
I changed the intake elbow before testing for the second time (in my update post with the details it was the first one). The changes were not noticable.

During idle I think it doesn't matter, and the test it self only goes to 2500rpm. I think that crack has affects starting at the first VRIS and above.
 
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