lots of carbon emmited!!

[grave77]

I had this problem recently, my car is running lower mileage than before ... torque is great engine runs smooth ... no hesitation at all ... but when I changed the spark plugs it was plated with carbon, also the exhaust is totally plated too. It seems like injecting more gas in the engine but I can’t seem to know why?!

[winfred]

check the common parts first, tune up, look for air leaks, fuel filter, that stuff needs to be looked at/changed before you do anything else, that will most likely solve the problem and if not you will not be be fighting possible worn out mantainance parts looking for the real problem

[grave77]

Well... I had this problem long time ago, but the engine torque was also low, I checked air leaks, so I changed are tubes and regulator valve I also changed the fuel filter and air filter, oil filter and spark plugs, I have also changed the distributor cap and high voltage coil too finally I changed the AFM too since the resistive line was wiped off. I have the injectors in my suspicion list. Any idea???

[stu1]

Enigne temperature sensor possibly? DME thinks car is cold so richens up the mixture.

Stu.

[Derek A.]

How far are you driving? Winter time will cause a decrease in fuel economy and these cars do not like to be started and shut down without being warmed up and driven.

[shogun]

Do you have the correct spark plugs inside.
Have a look here under spark plug conditions, how they look under different conditions and what you can "read" from it
http://www.vinesauto.com/techinfo.htm

[grave77]

This might be the one, but I can tell u here that I disconnected the O2 sensor 2 years ago, my ran very smooth without any carbon leftovers, now it does, can u tell me exactly where is the temperature sensor? And is there a way to bypass it for test sake?
My car really chokes when I full throttle until it’s warm. Sure u can see the black smoke in the mirror. And u smell the gas too.
I use BMW Bosch original spark plugs and they r new too, no signs but the powdery carbon buildups.

[JonE]

Running correct octane of gas for your application?

[grave77]

yeh sure ... I think it's octane 95 unleaded. what makes me wonder more that the torque is great !! it burns out with 265/35/18 wheels but I'm dumping like 35% of my fuel in carbon wastes... which I think is too much, to imagin the thing .. if u stand beside the exhaust for 2 min u will smell burnt gas on ur T-Shirt! as if u washed it with gas.

[grave77]

I read ur comment, sorry I didn’t reply so soon. in Dubai we have 2 seasons ( summer and super summer ) so don't worry about the cold weather :) the minimum was 15 C I don’t know how much in F ?? maybe something like 60 or 70, summer time we reach to 100 - 110 F that was from my cars temperature sensor. also the problem started in the end of the summer time when the weather was still hot. I think all of u wonder why don't I go and connect it to a diagnostic tool. the answer is that I can't find anyone in my neighborhood with it. all of them use their common sense which is mostly in accurate. that’s why I need some tips to start with then I can pin point the problem.
one guy told me that if u drive over 150,000 K then u need to change ur middle muffler the one after the catalytic converter. and by the way my catalytic converter is chipped off and replaced with Nissan Safari semi muffler pipes. ( it added few HP to the ride ). and that time it was running smooth without any wastes.

[grave77]

Yes ... Bosch original. I wrote about the spark plugs under Stu1 check it out.

[JonE]

Well, your 95RON octane might be about 91AKI octane rating, and I know the stock m30 engine runs very well on 87AKI. Is the engine chipped? I now run about 91AKI only because my m30 is EAT chipped. Don't know if this would contribute GREATLY to your problem, but something to consider. Did you say that you are running without a O2 sensor? If so, it will be running pretty rich when warmed up, wouldn't it? Could this carbon have been building up slowly over that last two years? Maybe now it's reaching a "critical" point, but, "torque" is great since all that carbon has effectively increased your compression ratio slightly?
Just my 2 cents.

[grave77]

well ... that takes me a while to think about, maybe I need to screw with the DME to figure it out. I mean to fool the DME input signal coming from the O2 sensor plug. do you think that’s possible?

[JonE]

How ever you slice it, it sounds as though the engine is running too rich. As I understand it, the O2 sensor does nothing when engine is cold, but starts to "work" when engine is warmed up. Perhaps it is not working correctly and DME still thinks the engine is cool (as another poster stated above) and is making it run rich all the time. This would probably also happen if there was NO o2 sensor present, right?
Hopefully someone else can contribute on this topic as this runs the depth of my knowledge on it.

[grave77]

well stu1 said about the temperature sensor giving the DME a signal that the engine is still cold!
but I also know that the AFM has an air temperature too, does this affect the change in the mixture?

[grave77]

I just wanted to say that I have solved the problem, it was due to 2 reasons mainly the AFM had its resistance changed due to the resistive film scratched and fed away, the second was the injectors were dirty and they needed the cleaning aid. Now it runs much better with the normal emission.
I had one small question for the specialists: what do you do if the diagnostic tool gave an unknown reason for an error. I had 1 for transmission and 2 for the engine including the mixture control (before changing the AFM) any one knows what can we do in such case?

[grave77]

Yeh Mark, I bought a new one (O2 Sensor) when u said so in the e-mail, I have wrote in today about the latest results, mostly the reason was the AFM it was totally out since the resistive line was faded away and the overall resistance was changed. I can give it like 80% of carbon emission was because of it (AFM).
My question now is that how can I know about the unknown errors appearing in the diagnostic tool? I had 2 in the engine and one in the transmission.
by the way the engine runs much better after the replacement of the AFM and O2 sensor. I'm only in need of the EAT chip now or the one u said that u can write for hotter weather.