Excess carbon out of tailpipe.

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Thread: Excess carbon out of tailpipe.

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    Default Excess carbon out of tailpipe.

    My '06 Tacoma V6 was recently in the shop for some warranty work to replace a bad power steering pump. While it was there, I wanted them to fix 2 other problems. One problem is the TSB concerning the occasional hard start issue, where the engine will crank but not start until the key is switched off and I try to start it again.

    The other problem I want them to fix is where carbon, mixed with moisture that is in the atmosphere (I live in Florida where the humidity is high), splatters on the paint and bumper above and behind the outlet of the factory exhaust. It has been doing this for a while, and the carbon is very hard to wash off. It seems I can never get it all off.

    I have noticed quite a few Tacomas around, and most of them are clean. Although I have seen some carbon on a few, none are as bad as mine. That tells me it isn't normal.

    My guess is that it is running rich, which is causing excess carbon. But the dealer found nothing wrong. The service guy said all pressures, flows, and temperatures seem normal, and that they can't find anything that would cause it.

    A while back, I removed the secondary air filter (which made absolutely NO difference in how it runs, power output, or MPG). I took some spray carb cleaner and, after placing a short 2x4 between the seat and accelerator pedal to keep the engine speed up, sprayed down the intake tract.

    I saw what looked like a sensor (probably MAF) that was a few inches inside the tract. I sprayed it well, concentrating on the sensor, because I do know a dirty MAF can cause issues. The previous owner had installed a K&N filter (which I replaced with a Purolator, again noticing no change in how it runs, power output or MPG), and I know that K&N filter oil can foul MAF sensors.

    After using the whole can, I cleaned the carbon off the paint as good as I could. After driving it several thousand miles, the carbon is back. Not only did using the spray carb cleaner not change how it runs, power output, or MPG, it still puts out too much carbon.

    Does anyone here know what could be causing the excess carbon output? I figure that IF running rich is causing it, then my MPG probably is suffering as well. I'm hoping the problem can be resolved, not just so the paint can stay clean, but so my MPG may increase, even if only by a small amount.

    Anything you guys know that I can tell the dealer to look for will help.

    Thanks, William
    '06 Tacoma TRD Doublecab 4wd
    Rear locker mod, 3" Skyjacker lift struts, Skyjacker rear springs and shocks, home made front spacers for 3/4" more front lift, Roadmaster rear overload springs for 7/8" more rear lift and less rear sag under load, more to come...

    '06 Yamaha Wolverine 450 sport/4wd ATV

    '08 Yamaha FJR 1300 Sport/Touring motorcycle

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    Veteran Member 05Moose's Avatar
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    Default Re: Excess carbon out of tailpipe.

    You realize that we all have a lot of carbon coming out the tailpipe since they all run rich? Any pics to show how yours is "excessive"?

    I have to rant...I love how everyone calls the carbon filter a "secondary air filter" even though it's not an air filter at all. It just keeps gas fumes from leaving the engine and adding to pollution. Those fumes get trapped in the carbon and then sucked back into the engine when you start it back up. So by removing the carbon filter, everyone's just venting those fumes into the atmosphere instead of using them when the engine is running. Might as well leave the gas cap off too. Personally, when I pay for all that gas I like to use it in running the engine rather than just letting it evaporate into the air.
    '05 4x4 DC LB SR5 (LSD & Tow Pkg), Timbrens, AAL, 5100s (.85), Front Diff Drop, Owned: 12/3/04
    Mods: Fog, Map/Dome Light, Illuminated 4wd Switch, Washable Cabin Air Filter | & 2010 Highlander 4WD

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    Default Re: Excess carbon out of tailpipe.

    Quote Originally Posted by 05Moose View Post
    I have to rant...I love how everyone calls the carbon filter a "secondary air filter" even though it's not an air filter at all. It just keeps gas fumes from leaving the engine and adding to pollution. Those fumes get trapped in the carbon and then sucked back into the engine when you start it back up. So by removing the carbon filter, everyone's just venting those fumes into the atmosphere instead of using them when the engine is running.
    A better word is absorbed. It is an activated carbon element, much like the charcoal canister for the EVAP system. The only time the carbon element is useful is when the engine is shut off after use, when small amounts of atomized gas are left in the cylinders and evaporate. The EVAP system does the rest. This was mandatory for CA emissions only.

    The fuel tuning for most modern engines typically centers around catalyst efficiency. That's the purpose for closed loop operation. If the A/F ratio were out of spec, the ECU would attempt to correct it using short term fuel trims. If that fails and the A/F ratio is still out of spec, the check engine light comes on.

    Toyota should have mounted the tailpipe on the Tacoma like the 1st gen Tundra: at a downward angle. This allows the accumulated condensation to drip out of the tailpipe instead of splattering on the body panel when it's expelled during a sudden engine load change while driving. In humid areas like Florida, the moist air ingested by the engine will produce much more water in the exhaust (water is a normal by-product of combustion) and splatter more of the soot from the tailpipe onto your body panel.

    The engine will lean out in hot weather, so you'll see this less often. Most people notice the engine enleanment as a reduction in power.
    2005 Tacoma Double Cab V6 4x4 w/ TRD Off-Road pkg., Auto
    1991 MR2 V6 (1MZFE)

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    Default Re: Excess carbon out of tailpipe.

    05Moose: No, I don't have any pics of it. But I do know that, although I have seen SOME carbon on other Tacomas, I have seen none as bad as mine. And I don't see the need to prove ANYTHING to you.

    And I was only calling the carbon whatchamacallit what I've heard others call it. Sorry if that offends you, but I didn't know what else to call it. I called it by a name that would allow others to know what I was talking about.

    It worked, didn't it? Didn't I succeed in calling it by a name that allowed you to know what I was talking about?

    And by the way: The minuscule amount of gas fumes ABSORBED by the carbon wouldn't make any measurable difference in fuel economy. Way more fumes are absorbed by the carbon canister. Maybe that's why the carbon whatchamacallit is so thin you can see through it, because there is very little to absorb?

    Not only that, for the gas fumes to make their way from the engine to the intake plenum, into the filter housing, through the filter, down the intake tube, and out of the air inlet, they have to be displaced by air.

    How is air going to enter the intake in such a way that the fumes are pushed out into the atmosphere with the engine not running?

    And the total volume of the entire intake system could not possibly be taken up entirely by the gas fumes, so it's not like the fumes will totally fill all volume inside the entire intake system.

    And when the engine starts, those gas fumes still sitting in the intake would be sucked into the engine anyway.

    I think the only reason why the carbon gas fume absorber is needed (is THAT a better name for it?) is so that Toyota could appease California's very strict environmental wackos. Maybe Toyota saw a need to "go the extra mile" so they would take it easy on them? I don't know. I do know at least some of the other brands don't use such a device.
    Last edited by William1; 06-13-2009 at 03:41 PM.
    '06 Tacoma TRD Doublecab 4wd
    Rear locker mod, 3" Skyjacker lift struts, Skyjacker rear springs and shocks, home made front spacers for 3/4" more front lift, Roadmaster rear overload springs for 7/8" more rear lift and less rear sag under load, more to come...

    '06 Yamaha Wolverine 450 sport/4wd ATV

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    Default Re: Excess carbon out of tailpipe.

    Anyway, here's an update.

    My check engine light came on a few weeks ago. The dealer mechanic found a bad catalytic converter, the second one on the passenger side. It was replaced at no cost under the emissions warranty.

    Then the check engine light came on again. I took it back to the dealer.

    This time, they replaced the first passenger side and first driver side converters. So the only original converter on it now is the second driver side converter.

    The technician also damaged an O2 sensor, so he replaced that as well.

    I don't know why they didn't just go ahead and replace the last of the 4 converters. After all, first 1 goes bad, then 2 more. Wouldn't it make sense that the 4th one may very well be on it's way out as well, and that maybe they should replace it too?

    Anyway, I also did a spark plug change. For some dumb reason, I was thinking they were 100,000 mile plugs like some GM vehicles have.

    The plugs were the originals, and I have 62,000 miles. The gaps were eroded away to at least 50% more than the .043 inch gap specified in the owners manual. And one plug looked as if it may have been leaking compression pressure from where the outer insulator fits into the steel base.

    One question: Does anyone know why Toyota used NGK plugs on the driver side, and Denso plugs on the passenger side?

    So now I have new plugs. The old ones may have been the cause for the carbon, since they may not have been burning the fuel mixture completely.

    I managed to get all the carbon cleaned off the paint, and half of it cleaned off the bumper and fender flare by using rubbing compound. So now I will just drive it and see what happens. And if I get a chance to do a trip on interstate, I'll also measure the MPG to see if there's any improvement there as well.
    '06 Tacoma TRD Doublecab 4wd
    Rear locker mod, 3" Skyjacker lift struts, Skyjacker rear springs and shocks, home made front spacers for 3/4" more front lift, Roadmaster rear overload springs for 7/8" more rear lift and less rear sag under load, more to come...

    '06 Yamaha Wolverine 450 sport/4wd ATV

    '08 Yamaha FJR 1300 Sport/Touring motorcycle

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    Default Re: Excess carbon out of tailpipe.

    Toyota uses NGKs in one head and Densos in another because of their contracts with both suppliers. In order to be fair to both of them, NGKs come down one line, and Densos on another so there is no favoritism on the manufacturers part, which could infringe on their supply contracts. They are equivalent parts, so there shouldn't be too much deviation between the two heads.

    You'll usually see it in Toyota V6s and V8s. The 4 cylinders get either 4 NGKs or 4 Densos depending on rotations. Though, the 2GR-FE and 2GR-FSE (and other direct injection motors) only use Denso long life iridium plugs, since there is no NGK equivalent.

    I normally run 91 octane as I've noticed the soot is much worse on 87 because the ECU retards the timing (plus I like the extra torque output). Surprisingly, in this rather cool weather for southern California, I haven't had any black carbon on my rear body panel.
    2005 Tacoma Double Cab V6 4x4 w/ TRD Off-Road pkg., Auto
    1991 MR2 V6 (1MZFE)

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    Default Re: Excess carbon out of tailpipe.

    Quote Originally Posted by Jason.MZW20 View Post
    Toyota uses NGKs in one head and Densos in another because of their contracts with both suppliers. In order to be fair to both of them, NGKs come down one line, and Densos on another so there is no favoritism on the manufacturers part, which could infringe on their supply contracts. They are equivalent parts, so there shouldn't be too much deviation between the two heads.

    You'll usually see it in Toyota V6s and V8s. The 4 cylinders get either 4 NGKs or 4 Densos depending on rotations.
    That's kind of strange of Toyota. WTH don't they just put the same plugs in all the holes for a given engine. Rotate between brands on each engine, instead of LH and RH heads. So does the Owner's Manual or Factory Service Manual say to put different brand plugs in each head? :crazy:

    BTW - my tail pipe does have some black soot in the bottom part of the pipe, but it never pukes soot onto the fender behind the tail pipe tip. I get about 23~24 MPG on a long hiway cruise at 65~70 MPH. 2005 Xtra Cab, V6 with 5-speed automatic.
    Last edited by SuperBusa; 06-18-2009 at 01:59 AM.

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    Default Re: Excess carbon out of tailpipe.

    Quote Originally Posted by William1 View Post
    05Moose: No, I don't have any pics of it. But I do know that, although I have seen SOME carbon on other Tacomas, I have seen none as bad as mine. And I don't see the need to prove ANYTHING to you.

    And I was only calling the carbon whatchamacallit what I've heard others call it. Sorry if that offends you, but I didn't know what else to call it. I called it by a name that would allow others to know what I was talking about.
    Hey, didn't mean to offend and I wasn't trying to pick on you. Everyone calls it a secondary filter without any idea what it does. Sometimes our comments get an unintended inflection that can be taken the wrong way. That's just a risk of using a forum.

    On the other note, my rear fender gets black too (although with a white truck it's not real noticeable until you run a towel or finger across it). So many people complain about it that it made me wonder what you would define as obsessive. I wasn't implying that yours wasn't excessive, but since I'm a visual person (as probably half the population) a picture would do wonders for understanding how yours compares to mine. Maybe seeing a picture I'd be able to say "that looks just like mine". On the other hand, I might give the reaction of "whoa, that's a lot!"
    '05 4x4 DC LB SR5 (LSD & Tow Pkg), Timbrens, AAL, 5100s (.85), Front Diff Drop, Owned: 12/3/04
    Mods: Fog, Map/Dome Light, Illuminated 4wd Switch, Washable Cabin Air Filter | & 2010 Highlander 4WD

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    Default Re: Excess carbon out of tailpipe.

    I have never seen any black soot on my fender ... I only see it on the inside (mostly the bottom bottom half where the condensation lays) of the tailpipe end. I don't baby my truck that much either ... so it gets plenty of heavy throttle use.

    I'm thinking the ECU isn't programmed properly on the OP's truck. What's the dealer think about reflashing your ECU in case it was programed to rich from the factory?
    Last edited by SuperBusa; 06-20-2009 at 02:08 AM.

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    Default Re: Excess carbon out of tailpipe.

    I get a TON of black carbon on my fender during the winter. I've cleaned it with a soft microfiber towel (further cleaning the area with clay bar too) and put on extra coats of polish to keep it from staining the paint. I've done a spark plug reading when this occurs, and the spark plugs actually look quite good. They are quite clean and without any black carbon a poorly tuned engine would show on the plug. I run iridium plugs gapped to 0.032 (OEM is 0.044).

    Only during the summer does it stay on the bottom of the tailpipe.

    I regularly use 91 octane, and during the winter, the power is great. I rarely have to rev it above 2500rpm, but when I get on the freeway, I usually punch it to get up to freeway speed (70mph here). The short on-ramps are particularly hazardous. This is usually when it splatters on my rear fender.

    I also run 10W-40 synthetic. I'm probably gonna move to 5W-40 at my next oil change. I only run that weight oil because of the piston slap that annoys me. I use to use 5W-20, but during freezing cold starts, the engine sounded particularly bad. With 10W-40, the piston slap is still there albeit less noticable, and at least the cylinders have a little more cushion against the blows of the pistons. I wonder what the friction reducing moly resin coating on the piston looks like after all of that scuffing.
    Last edited by Jason.MZW20; 06-20-2009 at 05:11 PM.
    2005 Tacoma Double Cab V6 4x4 w/ TRD Off-Road pkg., Auto
    1991 MR2 V6 (1MZFE)

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    Default Re: Excess carbon out of tailpipe.

    My 2.7 usually only has black in the tailpipe. But I do notice a little increase when I use cheap gas. It seems to be less using a "top tier" gas like Shell or Chevron.

    Hey Jason.MZW20,

    My 2.7 also has piston slap during cold starts (below about 35 degees). The best oil I've found so far without going too thick is Red Line 10w30. Way quieter than Mobil 1. During the summer I'm using PP 10w30, but will switch back to Red Line in the winter. The Red Line oil doesn't drain off over night as much and leaves a good coating. I emailed Red Line, Royal Purple and Mobil 1 and all three said a thicker oil won't drain down as much and that a 10 instead of a 5 would still flow well enough in the winter.

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    Default Re: Excess carbon out of tailpipe.

    So far, the truck is doing much better. Not only is the carbon splatter almost non-existent, but the fuel economy seems to be better. It's been about 7k miles since the new converters and new plugs, and all is well.
    '06 Tacoma TRD Doublecab 4wd
    Rear locker mod, 3" Skyjacker lift struts, Skyjacker rear springs and shocks, home made front spacers for 3/4" more front lift, Roadmaster rear overload springs for 7/8" more rear lift and less rear sag under load, more to come...

    '06 Yamaha Wolverine 450 sport/4wd ATV

    '08 Yamaha FJR 1300 Sport/Touring motorcycle

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    Veteran Member Negra's Avatar
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    Default Re: Excess carbon out of tailpipe.

    Stop buying cheap fuel and many "issues" will likely go away.



    The trouble with the world is not that people know too little, but that they know so many things that ain't so
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    Default Re: Excess carbon out of tailpipe.

    I never noticed any difference between fuels. In fact, the carbon splatter is almost nonexistent now, and the fuel I buy is basically no different than before. So that indicates that the type of fuel wasn't the cause.

    Besides, I usually try to buy fuel from reputable name brands anyway. I even use Shell at least half the time, just like mdbrjb said he does, and he said he noticed less carbon with Shell. I used Shell just as much before the plugs and converters were replaced as I do after. So no, the fuel wasn't the cause of MY issues.

    And since replacing the plugs and catalytic converters took care of the problem, and since the converters quit going bad after replacing the plugs (one of the four converters is still original), and since my fuel economy has also increased, that also indicates the type of fuel isn't the cause.
    '06 Tacoma TRD Doublecab 4wd
    Rear locker mod, 3" Skyjacker lift struts, Skyjacker rear springs and shocks, home made front spacers for 3/4" more front lift, Roadmaster rear overload springs for 7/8" more rear lift and less rear sag under load, more to come...

    '06 Yamaha Wolverine 450 sport/4wd ATV

    '08 Yamaha FJR 1300 Sport/Touring motorcycle

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    Default Re: Excess carbon out of tailpipe.

    Quote Originally Posted by Negra View Post
    Stop buying cheap fuel and many "issues" will likely go away.
    What would be considered "cheap" fuel? Wal-Mart, Sams Club, Costco, QuickTrip? And how would I go about verifying rather or not they have cheap fuel in there tanks? Doesn't it likely all come from the same refinery here in Texas? Where do you get your fuel so I can try it out and see if the sulfur smell and soot issues go away.

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