mx5cartalk.com

So on idle when cold my car blows massive amounts of carbon all over the ground.
Also I noticed a liquid dripping off the exhaust tip from the inside.
Unsure of it's unburnt fuel or not.
Don't know the condition of the cat but when I installed it 6 months ago it was fine.

Any ideas one what's causing this?

I'm running 17 degrees adv timing.
Brand new o2 sensor.
Brand new leads.
Brand new plugs.
Brand new Afm.
Brand new tps.
Standard ecu.

The car seems to perform fine so I don't think it's effecting performance but it does leave a very bad mark everywhere I go.
Please help.

Anyone have any ideas?
Is my timing destroying my air fuel mix?

Its winter. Due to the cold air and very cold coolant when cold, the fuel particles dont vapourise well in the manifold, so the ecu must compensate by richening up the mixture. This is the carbon when cold.


The liquid is water (condensation) in the exhaust that builds up overnight, and with the carbon mixed in it might look a little like fuel.

Timing never will affect mixture.


TL;DR: all good mate

Dann

....so what is different about a mx5 such that other cars don't ?? Or why did Mazda do this when others didn't??

Ahh I see,
Thanks dann, that makes it Alot clearer.

Yet a good point gslender.

It may be due a new coolant temp sensor some time. I really wouldnt stress about it though.

G:
Thats a very naive comment from a bloke as sharp as you. Of course all cars richen up in the cold and gather condensation in the exhaust. It depends where you live and where the car is parked to some degree though.

Dann

Cool cheers.
I'll look into that cool temp sensor.
Thanks dann

Chris.

Ok so after closer inspection, I have found that my coolant temp sensor is basically broken in half where the plug comes from the thermostat and turns into a wire.
(I'm assuming that this is the temp sensor)
Would this have an impact on the issue I'm having?
Also this probably explains some of the rough power lacking in early
Mornings.

So I have had a quick look and can find where to buy a new sensor.
As far as I can see I need a sensor AND plug with wire.
I currently have half a sensor with no plug on it and a wire hanging next to it also with no plug.

Is a wrecker my best bet or are there ones out there to buy new.
Mx5 parts uk sell the sensor but not the plug to match it.

I feel useless.
Any ideas?

Chris.

Is a wrecker my best bet or are there ones out there to buy new.

There is a white NA6 being wrecked at Greenacre in Sydney, maybe they will have what your after.

Forget address and phone number at the moment, but they are selling some parts on Ebay. I'll look for the number tomorrow.

Off the top of my head, this sensor is ONLY responsible for for turning the fans on.

Youll see its on the radiator side of the thermostat, so it wouldnt seen any temp until the thermostat opens, so it would be useless as the cold start ecu sensor.

So its the sensor at the back of the head (under the coils) that affects cold starting.

Dann

NitroDann wrote:Thats a very naive comment from a bloke as sharp as you. Of course all cars richen up in the cold and gather condensation in the exhaust. It depends where you live and where the car is parked to some degree though.

Dann

Dude I'm aware all cars have cold starting cycle. What I can't understand is why out of the 4 cars I own, the mx5 is the only one that does this.... I was thinking it was a rich fuel O2 sensor fault, but it still dumps a fair bit of black carbon along with the water. Maybe it will go away after a few more months ??

There are two temp sensors. One at the front (that control the fans), and one at the back of the head that goes to the Ecu. It could be a faulty sensor.... Might be my problem too.... Does anyone know the voltage ranges of a good sensor? Is it a ground to earth with the Ecu supplying a steady voltage etc?

About 15 kilo ohms at -20c
2.5 Kilo ohms at 20c
And 300 ohms at 80c

Dann

Ahh yes.
I have located the actual temp sensor.
Your right I was looking at the fan signal sensor.
I haven't tested the temp sensor but I ordere a new one since I don't know when this one was last replaced if ever.
eBay $40. Not bad.
Hopefully this will help my issue.
Thanks dann, very helpful.
Chris.

NA6 has three temp sensors: one at front & two at rear.

Ok after much waiting and gurneying carbon off driveway,
My new temp sensor arrived yesterday.
Installed last night and tested for the first time today.
Perfect!
Started this morning, 4 degrees outside.
No smoke, no spitting carbon, just a litle condensation.
Also I noticed that the auto choke actually worked properly for the first time.

Slender this may be your problem also.

Thanks guys for the help.

Chris.