William

My '06 Tacoma V6 is currently in the shop for some warranty work to replace a bad power steering pump. While it is 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

William

So I guess no one here has experienced this or has no idea of what to check?

William

Okay, here is an update.

Two weeks ago, my check engine light came on. It just so happened to be that a couple of days later, I was having a tire rotation and balance and alignment done, and they found a bad driver side wheel bearing. So I took it in for warranty work to have both issues fixed.

The technician found a bad catalytic converter. They replaced it. I really can't tell there is any improvement when it comes to power. If so, it is so small an improvement I can't definitely say. I haven't had a chance to measure gas mileage yet, but my guess is that if the converter wasn't bad enough to affect power, it didn't affect mileage.

Makes sense, anyway.

As far as the carbon issue, if the problem with the converter was causing it to not get hot enough to burn any unburned fuel completely, then I can see how a bad converter could cause the carbon splattering.

Does that make sense to you guys?

William

Update number 2:

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

The first time, they replaced the second passenger side catalytic converter. This time, they replaced the first passenger side and first driver side converters. So the only original converter 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.

DAN08

I think I may have the same issue on my '08. Can't say for sure that it is carbon but, it is a gray film that is difficult to clean just above the exhaust outlet. I also don't think I am getting as much as you are. But, I have not had any check engine lights. I have tried different types of fuel from all different locations and I still get it. I'll let you know if I ever come up with a solution.

William

Yes, that would be carbon. Apparently, some carbon on Tacomas is common. I've seen some on other Tacomas, but mine had way more than they did.

So far, the only way I've found to get all of it of the paint was by using rubbing compound. However, that only got about half of it off the fender flare and bumper.

Mine was putting out excess carbon way before I had the check engine light come on, so having the light come on apparently isn't an indicator of the cause of the problem.

In my case, the check engine light came on due to bad catalytic converters. So my guess is one of two things happened: Either the excess carbon caused the converters to go bad, or the converters being bad caused the excess carbon output.

In the case of the second possible scenario, the converters would have been bad or going bad long before the check engine light came on (as evidenced by the excess carbon), which I don't think is likely. The check engine light is a good indicator of such things as long as the O2 sensors are good. And mine were good.

So that leaves the first possible scenario, which would be excess carbon causing the converters to go bad.

And my guess there is that since I failed to change the plugs when they were supposed to be changed (waiting until 62,000 miles instead of changing them at 30,000), and since the gaps were eroded away 50% or more than what they are supposed to be set at, I think THAT is what caused the excess carbon, since the plugs weren't firing at peak efficiency.

So now that I have new plugs, I'm going to just continue to drive it and monitor the carbon splatter.

And hopefully I'll get a chance soon to check MPG on interstate. It got 21 MPG on interstate when I first bought it. The last time I measured on interstate, it struggled to get 14. I know my lift and bigger tires are responsible for part of the decrease. But I would like to find out how much better it does with new plugs and new converters.

So far, I've seen no correlation between which fuel I use and carbon output.

William

Almost 2 months have gone by, and there is very little carbon splatter. Looks like the issue has been fixed.

William

Another update:

It looks like the carbon splatter problem is still there. It's as bad as it was before. It had appeared to be greatly decreased a while, but I guess it just takes time to build up.

I tried using 93 octane gas, but that's made no difference, despite some on another topic here saying it helps. In fact, while it had appeared to be greatly decreased, I started using 93 octane. It didn't help to keep it from getting worse.

And despite what on here on another topic have said, it's not caused by "cheap gas". I normally run Shell, Sunoco, Hess, or Marathon. I occasionally will run other brands if necessary, but the splatter is consistent regardless of brand.

So that tells me that it has very little, if anything, to do with the octane and brand of gas.

Any ideas?