been playing around with my car tryin to figure out why im burning more fuel than i think i should and why my muffler gets heavily coated with black crap, i think carbon. also spark plugs seem coated with it too. anyways, i did nothing special like drive for a while or any of that crap, just took it in, 10-15min drive and got it done.

--------------------HC (PPM)------CO (%)------CO+CO2 (%)-----O2 (%)
CRUISE LIMIT: ---------150--------1-------------- 6 -------------N/A
CRUISE EMISSIONS:----126-------- 0.73----------16.13---------- 0.55
RESULT:------------- PASS ---------PASS---------N/A --------------N/A
IDLE LIMIT: -----------220 ---------1.2---------- 6 ------------- N/A
IDLE EMISSIONS:-------154-------- 0.23---------16.43------------ 0.01 RPMS=850 AT IDLE

anyone got any ideas what i can do to make these results better? why is my CO+CO2 on cruise and idle higher than the limit....these aren't required to pass in my state so my car still passed. anyways....I want to know how to lower my HC. maybe taking it in and having it dyno tuned with all the mods I have? any suggestions?

Thanks again guys, your always a good help!

 

The calm before the storm....

Just kidding... Old cars carbon regardless.

Perfect emssinons here, but still makes a little carbon build up.

 

maybe my foots a tad heavy then? explains my 12mpg city....ill try and granny it this tank. I know its an older car, but what makes older cars have more carbon? just a lil bit of everything being old? anything I can do to clear my carbon buildup?

edit:
oh ya, the emissions people were like. wow ive never seen a car like this! told them they probably see one at least once a day, just not with all the mods/addons i have lol, most of them thanks to your guy's help/suggestions.

 

Engine theory 101. Every time you run your engine, there are parts that rub together. They are protected from immediate catastrophic failure by the engine oil, but even with the oil there to lubricate and protect them, the parts slowly wear. There are a few parts that are important to us. In the cylinder head, the valve stems, valve guides, and valve seals are important. As the valves travel up and down, they rub against the guides. In addition, there is some wear on the valve seals every time the valve closes and opens. The job of the valve guides and seals is to keep oil in the top of the cylinder head from getting into the combustion chamber. As the guides and seals wear, they loose material, and the clearances around them get larger. Larger clearances means oil can start getting by the guides and seals, and into the combustion chamber.

The other parts that are important to us are the cylinder walls, and the piston rings. The rings rub against the cylinder walls, and provide a seal between the piston, and the cylinder wall. This holds in combustion pressure, but also keeps oil out. The rings scrape the cylinder walls, and push motor oil back down into the crankcase. As the rings and cylinder walls wear, the clearances get larger, and the rings don't fit as tightly against the cylinder walls. This allows a bit of space for more oil to get into the combustion chamber.

All this extra oil that leaks into the combustion chambers gets burned with the fuel. The oil, however, doesn't burn as cleanly or completely as the fuel does, and as a result it releases a lot more carbon than the fuel does.

When you are cruising, or at idle, the throttle is mostly closed. Under these conditions, vacuum in the engine (combustion chambers and intake) is very high. The high vacuum pulls more oil through the increased clearances. For this reason, your emissions are higher under cruise and idle conditions.

 

Are you running a stock ECU or aftermarket?

My VE runs almost identical numbers. Did it with stock and JWT ECU, but with the stock ECU, my exhaust was clean. with the JWT, I always have a layer of soot on the inside of the muffler.

Fun thing is when I take it to the road course and it all burns off. It'll turn my muffler blue and purple, with a ring of white haze about 1.5" in from the tip. pretty cool to see.


anyway, that's about what I run into with the HC emissions. I wouldn't worry about it.

 

so... i mean i guess just do an intense search for every harness connector related to emissions, and all your vaccuum hoses and stuff, and i guess seafoam it too. also, can you elaborate on your 'hesitation'? how does it comare to this http://forums.maxima.org/showpost.ph...6&postcount=48

 

would a compression test be to his benefit to see how the rings are?

 

running stock ecu. wish mine would burn off, yet it collects and looks all dry and just dark black, i want my chrome always!

so in theory im just getting some oil into combustion chambers. which would explain all plugs being sooted. to fix that id have to get new rings and valve seals?

thanks for your input guys

 

When your driving easy, like most of the population does, air flow/exhaust flow is "slow" compared to what airflow is at WOT.

When your driving easy deposits from the PCV system and EGR system collect on the inside of the intake manifold, the valves and combustion chamber.

Every max Ive worked on has had a thick layer of dark carbon lining almost everything on the engine. My 240sx, which is at 50% throttle or more most of the time, is very very clean. A light misting of oil every where and thats it. Same for a Z31 I worked on...

Sad thing is it gets 20mpg city/29 highway driving the same as the maxima and it gets 16-19mpg/28+highway. The 16mpg is chicago city driving and the 19mpg is columbus city driving....

One thing to check is your timing...it could be off. Id sea foam the crap out of your engine too, and drive it hard after ward too.

~Alex

 

On my 91SE with 256,000 original miles/original exhaust, the muffler/exhaust tips are perfectly clean inside. No black soot anywhere except on the underside of the tips where the condensation drains out in the morning. I've seen others around the same way.

 

then i guess you have a lot of gunners in your area..

 

is there anything that i could put in the oil or something to help seal anything that may be worn slightly? i dont have a timing gun or anything, anyone have a pic of the VE cps where they have it bolted, i have mine set to 4mm from where the right bolt(facing it) cant advance anymore

 

I didn't say that oil burning was your problem, I just explained why higher mileage engines always have higher emissions. If you don't see blue smoke coming out of the exhaust, and your oil level isn't dropping fast, then I wouldn't worry about oil burning. If you are seeing some blue smoke, or you are going through oil pretty fast, and don't see any big leaks, then a compression test might be in order.

 

already adjustment the problem?