Has anyone seen this before?

I just opened the air box after cleaning the car.


Should I worry ?

What can cause this?

 

Only thing I can think that would cause that would be a backfire

 

Afraid I couldn't tell you. Just replace the filter and keep an eye on it. If it happens again then there is an issue.

 

My guess is they sat something hot on there while working in the engine bay without the top portion of the intake on. Or it was laying on a table and they sat something on it.

I would doubt a backfire would locate that directly, but I'm not that smart either.

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Edit: Same with Loki below, I've been here since 2013 and never seen this before until this week with two instances, and the second instance that was posted shows it has to have been a backfire. Pretty crazy.

My initial thoughts (I am still very stupid) maybe some backpressure in the exhaust is leaving large amounts of exhaust gas/heat and unburnt fuel in the combustion area when the exhaust port closes and opens the intake port? Dunno. To cause that, I wonder if your exhaust ports are mostly blocked by carbon build up, which isn't uncommon for the rx8. Hopefully not, since that is a hard task to do without rebuilding the motor. You could try sucking ATF into the motor via the intake nipples, and letting it sit for a few days, but even then if it dislodges a large chunk of carbon buildup and that falls in to the housings then you're likely going to be in for a bad day.

And if ^ is true, then if there is any oil something flammable in the intake it could cause a backfire. Very crazy to see though.

I agree with the others though, I'd try just replacing the filter first and see if it happens again.

Do you know the previous owners driving habits? Did they premix? Oil type? Oil change intervals?

 

You're the 2nd person with this problem this week... and I don't think I've ever seen it in 12 years on this board. I agree that its either a backfire into the intake or someone got carried away with starting fluid. I don't know what you have to do to the car to backfire into the intake though, there's a lot of metal between the intake port and the burning bits. Is there oil in the intake tract? Is the MAF singed?

 

Maybe it was driven through a forest fire and inhaled some burning ambers. That would be one helluva backfire to get into the intake air filter. IIRC isn't there a factory mesh too. Your MAF would be singed wouldn't it?

 

yes very strange