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I just installed a MBRP stainless steel cat back system...and there is a small trail of oil on the inside of the pipe....I think it was coated in oil when it was in the box...but I'm not sure. And when I'm in park...if I hit the throttle to let someone listen to it...it blows some black smoke. Is this normal with no other mods?
 

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my LBZ throws a little smoke in stock form with a straight exhaust..
 

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Yeah when I got my 4in. on my truck it was blowing a little smoke at idle for a few hours afterward. Think it was just burning stuff off of the inside of the pipe.
 

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besides the oil in the pipe, your cat will build up unburt fuel and carbon and when you get on it it will blow out as smoke; mine has a full turbo back and it doens't do that anymore but at idle for any amount of time it'll put out a blue haze from loading up. i didn't know tomany secrets until this forum but something else they have told me to do is a egr blocker plate and fingure stick, the plate keeps all that black out of your intake, and the stick blocks the codes
 

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I have no modifications to my 04', but smoke on idle and when "goosing" the throttle in park was the product of 8 faulty injectors. This of course is an 04' with the recalled injectors, or what the dealer told me was recalled injectors.

I have also been told algae buildup may cause a little puffage and/or even cause injector malfunction. Supposedly this can "fool" the delaership into diagnosing faulty injectors. This of course is one of those "what I have heard" storys.
 

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I have no modifications to my 04', but smoke on idle and when "goosing" the throttle in park was the product of 8 faulty injectors. This of course is an 04' with the recalled injectors, or what the dealer told me was recalled injectors.

I have also been told algae buildup may cause a little puffage and/or even cause injector malfunction. Supposedly this can "fool" the delaership into diagnosing faulty injectors. This of course is one of those "what I have heard" storys.
ya the 01 thru 04 duramax known also as the LB7 had some injecter troubles but they had them fixed buy the 04.5 duramax known as the LLY..the LB7 smokes more stock then any other duramax seeing most ofem don't have cats..
 
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