TransAmWS6

After heads/cam I've been getting a lot of carbon build up above my exhaust tipsr. Any ideas on a way to prevent this or is it just something I'm going to have to live with because of the long tubes on ORY?

LS6427

iTrader: (2)

You are running rich. Check your tune. I have to clean my rear bumper once a week, because I'm running rich. But thats because I have so many miles on my engine and my cylinders are coming out of round and I have blow-by, which is making my PCM run me rich in the upper rpm range. My issue is expected and normal for a high mile (150,000+ miles) engine......you have another problem.

Black soot on the rear...is fuel from being rich.

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TransAmWS6

I had the car tuned a few months back. When they first strapped my car on the dyno they have to add fuel before they could run the car at wot because it was way too lean. I was getting the same amount of build up prior to my tune as I am now.

The only other ideas I have heard were that I should get some type of cat or move the exhaust back so the tips would stick further out past the bumper. I'm just trying to get so ideas before I buy anything or make any adjustments.

LS6427

iTrader: (2)

Well, there's an issue with it regardless. You need to find out why its running rich. I know why mine is and the only way to fix it is with a rebuild.

You need to find out your problem. Moving the pipes back will keep the soot off, maybe, but you'll still have an issue that you do not want.

It could be an 02 sensor issue. But I would have the tune checked by them if it was just a few months ago, tell them you think its running rich somewhere in the rpm range. They should check it for you for free or at minimal cost.....

But black soot is from running rich. If it was oil you would see white-blue smoke coming from the tail pipes. Coolant is also white smoke.....

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NVR_SPDS

iTrader: (39)

How old are your O2 sensors? If they are old, id replace them and check the harness to ensure the wires are good. I had an O2 issue before, where the sensor was reading lean, and trying to compensate by running rich. Turned out a wire was bad.

FiredUpZ28

I'd say its a mix of running rich and unfiltered exhaust. Either one could cause it, and both together WILL cause it.

LS6427

iTrader: (2)

Its not a matter of unfiltered exhaust AT ALL. My catless exhaust for the first 6 years with my 427ci left not a trace of black soot EVER on my bumper over my tailpipes. Its after passing 100,000 miles and my PCM started to adjust for my oil blow-by as my cylinders got out of round and made me run richer and richer over time.

An unfiltered exhaust with a PROPERLY tuned engine will leave ZERO black soot on the bumper.

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6spdchevy

iTrader: (2)

good info i also get like a black soot on my rear bumper and always wondered where the hell it was coming from btw i have 161k on my motor all stock

FiredUpZ28

Thats a really good point, I thought it was just catless exhausts but having no cat doesn't affect the mixture so theres no reason it should be black coming out of the pipes..... Thanks for the reality check