P0420 and P0106 - related?

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10-15-2008, 08:20 PM
Walsted

P0420 and P0106 - related?

My mileage went from around 29.6 to 27.7 for two tanks, so I pulled codes. Got P0106 and P0420. Did a pointy search on P0106, cleaned out the place on the intake where the vacuum line for the MAP sensor connects, and cleaned the electrical connectors on the valve underneath the MAP sensor. Cleared codes, but haven't driven enough for them to come back.

The cat has a little over 11 months and 22K miles on it. Is it likely that the P0420 was set by an improper fuel mix due to bad data from the MAP, or is it more likely that I need to get a new one (again)? The last one was installed by a shop on Hemphill, so it probably wasn't the highest quality piece on the market, but I was hoping for at least a couple of years out of it.

Thanks.
10-15-2008, 08:55 PM
gabkwong

Quote:

Originally Posted by Walsted

My mileage went from around 29.6 to 27.7 for two tanks...

Wow, I would be very happy if I get 27.7! Of the 9 years I have my NB, the best I ever (mostly freeway driving) was 27.
10-15-2008, 11:25 PM
johnwag

Check your O2 sensors. http://www.obd-codes.com/p0420

I've only had M1 miatas, and I'm starting to learn NB's. Where is the map sensor located on an NB?
10-16-2008, 06:11 AM
Walsted

Quote:

Originally Posted by johnwag

Check your O2 sensors. http://www.obd-codes.com/p0420

I've only had M1 miatas, and I'm starting to learn NB's. Where is the map sensor located on an NB?

If the P0420 doesn't stay cleared, that is the next step, and then the step after that would be getting a new cat. I'm hoping it stays cleared, though.

The MAP sensor on my NB is passenger side, along the fender about halfway back.
10-16-2008, 07:46 AM
POS Racing

Quote:

Originally Posted by gabkwong

Wow, I would be very happy if I get 27.7! Of the 9 years I have my NB, the best I ever (mostly freeway driving) was 27.

+1

I'd be even happier if our '02 that serves as daily driver would even get in the mid 20 MPG range!

Walsted did your car kick a CEL or were those just codes it had stored?
10-16-2008, 08:12 AM
Walsted

Quote:

Originally Posted by POS Racing

+1

I'd be even happier if our '02 that serves as daily driver would even get in the mid 20 MPG range!

Walsted did your car kick a CEL or were those just codes it had stored?

Those were stored codes. I wouldn't have noticed any problems if I didn't track gas mileage and scan for codes when I noticed an unexplained decline.
10-16-2008, 08:16 AM
POS Racing

Quote:

Originally Posted by Walsted

Those were stored codes. I wouldn't have noticed any problems if I didn't track gas mileage and scan for codes when I noticed an unexplained decline.

Is the cars normal route consistent enough to be able equate for that massive 1.9 MPG difference?? ;)
10-16-2008, 08:39 AM
Walsted

Quote:

Originally Posted by POS Racing

Is the cars normal route consistent enough to be able equate for that massive 1.9 MPG difference?? ;)

Yes, my life is that boring.
10-16-2008, 08:44 AM
POS Racing

Quote:

Originally Posted by Walsted

Yes, my life is that boring.

Bummer....
10-16-2008, 12:26 PM
Walsted

It's Dead, Jim.

After further testing, I have confirmed that the P0106 and P0420 are independent, the P0106 has been cleared/repaired, my O2 sensors are working, and my cat is dead.

Does anyone know of a place that has a decent cat (installed) for a decent price? As in just cut out the old, dead one and weld in a new that will hopefully last more than a year and let me pass the smog test.

Thanks.
10-16-2008, 12:30 PM
POS Racing

Correct me if I am wrong: If you car is not kicking a CEL won't it pass inspection as it sits?

Also no warranty on the 11 month old replacement??

Quote:

Originally Posted by Walsted

The cat has a little over 11 months and 22K miles on it.
10-16-2008, 12:49 PM
Walsted

Quote:

Originally Posted by POS Racing

Correct me if I am wrong: If you car is not kicking a CEL won't it pass inspection as it sits?

Also no warranty on the 11 month old replacement??

Since it stores the P0420, that code will come up when it is connected to the smog station test equipment. I don't know why it isn't triggering the CEL.

The place I got the last cat was one of those hole-in-the-wall places on Hemphill. They don't warranty converters, or maybe only warrateed to 90 days, or something similar.
10-16-2008, 12:53 PM
POS Racing

Before I would throw yet another :cat: on it I'd want to figure out why it smoked one in less than a year, unless you like buying a :cat: every year.

But that's just me! ;)

Ya got one of these deals yet? Looks like it could help ya pinpoint the problem - http://www.scangauge.com/
10-16-2008, 01:08 PM
Walsted

I've got the Harbor Freight CAN/OBDII code reader. I figured this one may have died due to the bad MAP readings giving a bad fuel/air mix, and it being a pretty cheap cat to begin with, but don't know if that is it for sure.
10-16-2008, 01:19 PM
POS Racing

The Scangauge will give ya the ability to measure the O2 sensors on an NB - http://forum.miata.net/vb/showthread...=scangauge+cat

Have you checked the O2 sensors? How many miles on your scooter?

Unless your Hemphill special was junk I still have trouble getting my head around a 11 month lifespan on a :cat:.
10-16-2008, 01:22 PM
POS Racing

I think trickyrix is our latest :cat: buyer, he should know of a TCB source for a :cat: !
10-16-2008, 01:48 PM
Walsted

I checked the O2 sensors with a voltmeter. The rear and front voltages matched, (varying from .2 to .7,) so I figure that there are no changes in O2 levels occurring between the sensors, hence the cat isn't doing anything.
10-16-2008, 02:01 PM
sammm

Quote:

Originally Posted by POS Racing

trouble getting my head around a 11 month lifespan on a :cat:.

Unless the coil pack is bad/going bad. That will fry a cat in no time.
10-16-2008, 03:01 PM
jrj512

Quote:

Originally Posted by POS Racing

I think trickyrix is our latest :cat: buyer, he should know of a TCB source for a :cat: !

I'm no trickyrix, but I just bought a cat from Flying Miata (or was it Moss?) about three weeks ago. Since I recently decided to move to STS2 next season where I can use a high-flow cat, I would be willing to sell my almost brand new OEM-style cat. It is on a '93. Does anyone know if they are the same for '93 and '99? If so, Walsted, feel free to PM me about a possible deal.
10-16-2008, 03:32 PM
Walsted

jrj512 -
Since mine has been replaced in the past by a universal cat, the OEM style won't bolt right up.

According to the Magnaflow web site, I need a Magnaflow 99204HM. (just ordered one.) I think my curent cat is a Catco. Catcos didn't have a real good reputation among the smog testers in California, but I usually got a few years out of them.

Thanks.
10-17-2008, 07:02 AM
trackdog

The O2 sensor after the cat does not affect performance or gas mileage, it is only there for emisions to measure the cats performance. It does not mean it is dead or necessarily going it just means that on that day it was out of spec. After resetting the CEL it may be months before it might see another trip. In forced induction cars we run richer than normal and sometimes get this CEL code, but it can be reset and go your merry way for a long time.

We also will trick the system by adding a resistor and capacitor to the rear sensor to give the ECU a constant good signal. No CEL lights come on and passes emissions. If we do not see a degradation in performance due to the cat performance then save a few dollars and leave it along.

Most likely your gas consumption was a different day of driving, not cat related. If your cat was really bad you would see restriction in the exhaust and seat of the pants loss in power.

Gary
10-17-2008, 08:25 AM
TurboDuane

Quote:

Originally Posted by trackdog

The O2 sensor after the cat does not affect performance or gas mileage, it is only there for emisions to measure the cats performance. It does not mean it is dead or necessarily going it just means that on that day it was out of spec. After resetting the CEL it may be months before it might see another trip. In forced induction cars we run richer than normal and sometimes get this CEL code, but it can be reset and go your merry way for a long time.

We also will trick the system by adding a resistor and capacitor to the rear sensor to give the ECU a constant good signal. No CEL lights come on and passes emissions. If we do not see a degradation in performance due to the cat performance then save a few dollars and leave it along.

Most likely your gas consumption was a different day of driving, not cat related. If your cat was really bad you would see restriction in the exhaust and seat of the pants loss in power.

Gary

+1 I've had a cat go bad. You will definately know when this happens, by the sound of rushing air, and very poor performance, and possibly the sound of marbles in your engine.
10-17-2008, 11:06 AM
Walsted

Quote:

Originally Posted by TurboDuane

+1 I've had a cat go bad. You will definately know when this happens, by the sound of rushing air, and very poor performance, and possibly the sound of marbles in your engine.

That would explain why I've been getting some pinging, lately. I thought it was just bad gas or something like that.
10-19-2008, 09:56 AM
mikeytx

Quote:

Originally Posted by Walsted

Yes, my life is that boring.

:rolleyes:
10-21-2008, 07:13 PM
doc

bad cat

Walstad
even if the code is held in the pc it will show as a code that has cleared on an inspection.
If the CEL is not coming on and you are getting a little pinging, it very well may have been a gas problem.
A bad cat usually will darg you down in performance badly.
The one I had that went bad was noticed when I gave a lot of pedal push trying to get in traffic it was a chug chug chug and top speed about 40 mph
I would not worry to much about codes that are cleared or that you have seen stored and cleared
Get all of them cleared and then give it a few days and test it again and see if they come back .
possibly someone could have removed the light from your cel so it cant come on so be sure it is working
Do let us know if it turns out to be a cat I for one am curious to know
10-23-2008, 09:02 AM
Walsted

Quote:

Originally Posted by trackdog

The O2 sensor after the cat does not affect performance or gas mileage, it is only there for emisions to measure the cats performance.

I figured the decrease in gas mileage was due to the P0106. If it doesn't go back up now that the vac port and electrical connectors are cleaned, I'll start looking for something else.

Quote:

Originally Posted by doc

...
Get all of them cleared and then give it a few days and test it again and see if they come back .

The P0420 kept coming back.

Quote:

...possibly someone could have removed the light from your cel so it cant come on so be sure it is working.

It works

Quote:

...Do let us know if it turns out to be a cat I for one am curious to know

I replaced the cat and the codes haven't come back after 50 miles. The old cat was one of those cheap "high flow" versions, the new one is the Magnaflow 99204HM, and the exhaust seems quieter, now.

Hope this helps someone.