Soot on bumper, any ideas?

maddogg20

New Member
Hey guys,

Just wanted to pick ur brains. I finally got my car running 1/2 way descent and besides an oil leak its driving really nicely. The only thing thats bugging me is that when I romp on it or rev it in neutral, itll puff out some black soot and its blackening the bumper, and the garage wall if I happen to be backed in lol, which I know means its running rich. I have already done a full tuneup on it, and even changed the 02 sensor, which helped a bit, but its still doing it. The catalytic converter is newish btw. What are the usual suspects that cause this on these kind of cars? Its a 1991 LS with 136k and a B18A.
 

Alvi84

New Member
Sounds like the valve stem seals or piston rings. Do you have much "blow-by" coming from the oil cap? Do you notice if it smokes on the rev up or when the RPM's are coming back down? Typically if you are creating smoke on the rev up I'd say the piston rings are suspect and if its on the way down, the valve stem seals.
 

maddogg20

New Member
I was wondering about the rings or stem seals being gone, but its not burning oil and making white smoke, its actually black which to me means unburned fuel. At idle it doesnt smoke at all but when I rev it up it puked the black stuff all over my garage wall, but it doesnt on the way down from a rev. Im just wondering why its running so rich despite me changing the components that commonly lead to a car running too rich. The check engine light isnt on either so im like hmmmm. I did check the o2 sensor with my volt meter and it is responding and reacting quickly so I know its not a lazy o2 sensor. Im debating on changing my fuel pressure regulator because I know that can cause it, but Id rather not if theres something else that happens to these kind of cars that usually causes this. Its not a huge deal that its doing it, I just dont wanna waste my cat you know.

Andy
 

maddogg20

New Member
oh, to answer your question, there isnt too much blow-by. Just what I would normally expect. lol it doesnt make the oil cap dance or anything when I have it sat on there not screwed down.
 


Alvi84

New Member
I've noticed that I seem to run a little rich in warmer conditions. Have you had any temperature changes where you are at? Are you running a stock ECU or tuned ECU? Does your car run at the normal temp range?
 

maddogg20

New Member
well itll still puff out the black after ive driven it for a while but it does it ALOT when the cars cold. It runs in the normal temp range, and its been a pretty steady 80 degrees here while I was driving it. I do think that there may have been alot of crap built up in the exhaust because it had a blown head gasket and was misfiring like mad when I got it. it probably cooked the cat so im debating on throwing a new one on. it also had some no name 4-2-1 headers on it so I dont know if thatll make a difference or not, in what it spews out lol.

ohhh, and btw where is the cat supossed to be located? because after I got the car I crawled under it and noticed that some dumbass had cut the triangle flange off of the headers and welded the cat directly to the pipe where the triangle flange was for the headers. I thought that it was supossed to be located further down the exhaust pipe but im not sure.
 


hidenplanvew

New Member
could be a fuel pressure reg. or spark or timming, injector, .. does it feel slugish? Temp shouldnt have anything to do with the amount of fuel being unburnt
 

maddogg20

New Member
It does feel sluggish. Like off the line it doesnt have crap on the bottom end then it gets all of its power at about 3800 rpms. I did check the timing and it probably needs to be set, but what is the spec for it. I even have the haynes manual and it mentions 14, 16, and 18 degrees before top dead center but it doesnt tell me what it should be set at. I will definitely retime it. The only reason I was suspicious of the coolant temp sensor is that I know on some other cars when the coolant temp sensor detects that the engine is cold, or the sensors bad, itll make the engine run richer to compensate for the colder/denser air.

U thinking it may be a timing issue? thatdd be awesome if the timing was the cause.
 

Tam4511

CI BOOST FIEND
as long as its not excessive that is normal. You can have your exhaust shortened so the muffler doesn't come out behind the bumper.
 
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