NB8A oxygen sensor

[EGG80X]

Just wondering if NB8A use a single wire oxygen sensor?











bloody idle dip is killing me

[Alex]

damn I thought you solved it, mine is still there too

[Okibi]

I thought it was a 4 wire oxygen sensor.

[Alex]

hmm a bit more research and this problem seems VERY common
and mazda it seems does know about it
old thread from 2000 but read here
http://forum.miata.net/vb/showthread.php?t=127446

Last week I finally took my car in armed with the info I had retrieved off this forum. I was ready for a fight but the service rep was very willing to deal with me and all the posts I had printed up. I showed him the one about uping the off computer idle. They did this and my idle dip has pretty much gone away. I say pretty much because I can see the tach bouncing up and down a little bit during warm up but very little and if I didn't have a tach I would not be able to feel the change in the rpm's. there is no longer ANY ROUGH IDLE problem; it is fixed to my satisfaction and I'm pretty particular. Have you gone in to your dealer and suggested this fix. I'm not saying it will work for you but it did work for mine and my car has had the idle dip problem from day one.

also read these, I don't have the time to right now my shift is nearly over
http://forum.miata.net/vb/showthread.php?t=251908
http://forum.miata.net/vb/showthread.php?t=250513

[EGG80X]

yeh its still lingering around, now its even more annoying....
The engine hesitate to accelerate below 3k rpm + the idle dip when its cold, and on top of that its bogs down on take off when the air con is on when the engine is warmed up

I already reset the idle via the Idle crew + new plugs and my leads and coil pack been replaced only a year ago

I reckon its the oxygen sensor.... feels like its running too rich, I can smell petrol fumes when I cold start the mx

I might try the fuel filter next......


but I have tried searching in miata.net for info about oxygen sensor... but not luck everyone is referring to 4 wire wide band oxygen sensor

[Steampunk]

It should be a 4-wire as my NA8 had one, which was a pleasant surprise.
O2 Sensors are generally not a weak point and should last 150,000km at least, but since you've done the process of elimination then this could be it.

[Garry]

All the 1.8 MX5's use a 4 wire sensor. Just have a look at the black plug at the top rear exhaust side of the valve cover. It should have 4 wires going through it. Two of them are black, one is blue, cant remember the other colour, white maybe. I dont think single wire sensors would pass any of the newer emission laws applicable to the 1.8's.

I'm not sure about them lasting 150,000km. My first one lasted about 50,000km and it's looking like the replacement one (genuine Mazda) is about to die now too at 120,000km. I should know this afternoon if I need a new one.

Have you checked you EGR valve. If it's leaking it can give you a funky idle amongst other things. It's mounted on the rear of the inlet manifold.

[Garry]

Apparently my o2 sensor is still OK. It's showing it's age by reacting a bit slower than it should but it's still OK. Maybe this one will get to 150,000km.

[EGG80X]

ahhh Cheers nice one Garry.....


Today its a bit weird no idle dip
Will check out the ERG valve tomorrow, its a bitch trying to source out a 4 wires O2 sensor with the OEM plug.... Splicing or soldering seems dodgying to me with all that transmitted heat from the exhaust, plus I don't want to pay a fortune for the factory one $330-360 seems like Bosch and Denso have OEM replacement but have to order overseas grrr!!!!!

[Garry]

EGGBOX,

Let me know if you find a source for an MX5 specific one. The tuner guy I was talking to yesterday warned against using a \"generic\" spliced in version as they aren't calibrated exactly the same.

[Steampunk]

I KNEW I had a link somewhere.
I've considered replacing mine for a while.

I hope this helps:

http://mymiata.paladinmicro.com/Miata4-WireO2.htm

As with actually buying them, eBay sells reputable brand name ones starting at $18USD.

[Garry]

EGGBOX,

I'm not sure if you've gotten around to replacing your O2 sensor but you should check your EGR valve. I found that mine was leaking around the valve stem. I replaced the valve and it's idling perfectly now.

To check it remove the valve from the car and try to blow through the top port. If it's OK you shouldn't be able to blow through it. If it's leaking from around the valve seal you should be able to clean it up and get it working again, but you will need to remove the solenoid on the top to open the valve to clean it properly. If it's leaking from the valve stem like mine you will need a new valve.

PS Mazda AUS want $AUS440 for a new valve, Mazda US want $US125 for the same part. Why are we always ripped off in Australia?

[EGG80X]

Garry,

I haven't replace it yet.. still got to try changing the fuel filter first...
but Denso does a OEM replacement 4 wire oxygen sensor for our NB part number #234-4144 which have to be ordered from the states because Denso Aus dont stock them....


oh btw where is the vaccum line for the EGR valve.....?

[Garry]

Thanks for the part number EGGBOX.

The EGR valve doesn't have a vaccum line, on an NB8B it's dríven by a solenoid thing mounted on top of the valve. I haven't looked at a NB8A. To check that it's sealing properly you will have to remove the valve from the car and blow through the top port.

Instructions here. http://www.mazda-speed.com/forum2/index.php/topic,7742.0.html

[EGG80X]

cheers Garry!!! you're the man!!!

just opened the EGR valve up this morning and wow!!! a thick crust of carbon build up.... cleaned her up and will see how she drive this arvo on the way to do xmas shopping hehe