Exhaust Stain - Causes?

I noticed this recently:



That stain on the paint above the tailpipe appears to be coming from the exhaust and it does not want to come off. I haven't had time to try with a lot of items, but a simple scrub does nothing. (would love detailing reccos but not the intent of this post)

My assumption is that these came after some hard towing sessions. Heavy headwinds, high temps and a travel trailer with the aerodynamics of a brick.

Thoughts on causes assuming it's coming from the tailpipe?

Usually exhaust black = running too rich. The air filter likely could need replacement but otherwise I have zero other leads. The truck only has 50k km (30k miles) on it. It's otherwise in ideal condition.

For context, this was the last towing session - hottest I have ever seen the truck. Ambient temp was 38C (100F), strong headwinds and the trailer that is less than 4k but terrible aerodynamics. But I am sure the stains were there before this trip.



Trip duration is low because I reset the app.

 

It's just crap from the exhaust. Have to scrub kind of hard to get it off.
May have to try a light abrasive polish to remove. I'm sure a detail guru will be along to help but

Cement seems to like to discolor by the exhaust easier than some other colors

 

I'm thinking you are probably right. Just debris and nothing sinister.

 

Mine is tuned to run pretty rich under load. I see a lot of 10-12 AFR when towing, and I don’t get that kind of discoloration on the paint above my exhaust tips. The soot from running rich mostly just accumulates on the tips themselves. Must be something else but probably not worth worrying about. I agree the cement color makes it more susceptible to showing stuff like that.

 

Probably a clay bar and some wax and you’ll be good.

 

That's normal. Mud flap contibutes to it being deposited on the fender due to air turbulence there. I guarantee every white truck shows that. Mine sure does. But it WILL come off.

 

The cause of your woes is the super rich afr your truck runs at.

 

bullydog leans it out right?

 

Might be time for a tune. Any recommendations @dirtydeeds ?

 

My truck did the same. I added a black chrome exhaust tip extended it out an inch or two and that was enough to fix the problem. If I remember correctly I used some polish and a foam applicator to remove it.

 

Depending on options chosen, you can get it to in certain areas of load.

 

Bullydog or CVC. But there’s places you want it to be lean.

 

Nothing to do with the exhaust but driving in S4 will shave about 25 degrees off your trans temp backing you off those yellow and red in the gauges.

 

Dear lord 253 degrees good catch. Yeah s4 going up ike hill in colorado i was at 204 degrees in TC and pan….

 

From my experience, it drops when the torque converter lock up regardless of gear. Just being in 4 wouldn't have helped. What's nice about the dashboard app is that a green circle goes around the gear number when the converter locks. You can immediately watch the temps drop.

 

And that's with a transmission cooler?

 

the difference is that s4 will keep it locked. You’re making so much power at the rpm it will be locked. It drops fast

 

Stock. Last year from the factory. Not exactly the most efficient though.

 

Hmmm... S4 doesn't keep it locked on my truck.

This was from the same drive. S4. If the torque converter was locked the display shows a green ring around the gear number

 

This

 

Does your truck have a custom tune?

 

My truck has the same buildup. Mesquite color with color matched rear bumper. Stuff makes color look faded around lower corner of bumper cap piece.

What to scrub with to clean it? Fine rubbing compound or something else? Just a rag and soap or pressure washer doesn't remove whatever it is.

 

No. Considering one though.

Now you guys have me questioning myself. I'll go for a ride tomorrow and test s4 lockups.

 

My converter locks and unlocks in S4 depending on load. The trans temps stay lower in S4 though due to it being a 1:1 gear ratio with the engine speed so there isn’t much TC slip happening even unlocked which keeps fluid temps down.

 

This could be the case - I just know from real world use the trans runs way cooler in S4.

 

Yeah, I have this too on my 2014. I'll hit it with the clay bar next time I wash her.

 

That matches my experience.

 

@Ericsopa these trucks are programmed from the factory to run as rich as 10afr in open loop.

my comment isn’t insinuating any type of a problem with the OP truck, it was solely intended to state the fact that a tundra runs rich, and is designed as such, and therefore you get soot.

to summarize, the soot is due to running rich. It’s normal.

 

Actually I deleted the post soon after posting it, not because I changed my mind, but because I decided it wasn't helpful. Particularly since the thread took a whole different direction, focusing more on xmsn temperatures.

I posted originally, because there were a couple responses that rightly or wrongly took your comment as indicating that there was a problem that needed addressing, i.e., " bullydog leans it out right?" and "Might be time for a tune. Any recommendations?" To which you replied, as if the OP really had something that he needed to do.

I'm not real sure what AFR my truck runs at in open loop, since it has an OV tune. But I do know that unless someone has something wrong with the engine management system, or the truck is never driven long enough to warm up, that engine is running in open loop very little. And I seriously doubt that bullydog will do much to lean out an engine while running in open loop.

My main point was that there is nothing abnormal about that stain. It didn't build up overnight, or with one trip pulling a trailer. It built up over time and is in no way an indication of a problem.

 

The difference between my last post and this post, your last post says: “I seriously doubt bullydog will do anything to afr when truck is running in open loop”

I can tell you exactly what afr you will be running with each specific option that the bullydog offers. None of anything that I post is intentionally misleading, nor is it a guess, unless I specifically say that it’s a guess.

sometimes I’ll answer with short incomplete sentences and facts, but always facts. Sometimes I’ll even answer without re-reading the entire thread which will make my answers seem erratic. I answer 100+ questions about tundras per day. That is literally my job.

I don’t know what OVtune does to the afr in open loop. But I do know that tundras run extremely rich in open loop and that’s why there’s all that soot all over the OP truck. A bullydog will reduce the door as a result of leaning out the afr.

I just look at the soot as status. It’s the result of having a truck that never breaks down