Black (smoke?) Cloud from exhaust at WOT

91BLOWNSC

Registered User
It seems that everytime I go WOT on my car it spews out a bunch of black crap from the exhaust system. This happens not only with my modified car but my friends. I took to understand that this means my motor was running to rich and was adding to much fuel. But when I ran the codes on my car, it said I was running lean on the left and right banks. Can someone tell me why this is and how is it possible I am running lean and still spewing out black crap when thats supposed to be a sign of running rich?

Thanks, Mark.
 
Me too

Hey Mark, I am also experiencing this problem, not more so now that I installed the new Charger and bigger injectors, but sometimes I still look behind me and see the cloud, gets kinda worrism huh? I would also like to know exactly whats going on, THanks MIke
 
Just a thought....

Here is what I have recently experienced on my '93 SHO...When the codes indicate a lean condition but your exhaust smoke is black, this could mean that the O2 sensors are not reading the exhaust gasses correctly. When they sense a lean condition, they trigger the computer to increase the fuel ratio. The richer the engine runs, the more contaminated the failing O2 sensors become. I would think that the CEL would come on when the sensors start to fail.
Like always, your situation may be caused by something totally different....
 
The easiest way to verify this is to check fuel economy over a week. I would tend to agree with Mr. Griggs. If the computer is saying the engine is lean, but you are seeing black soot at the tailpipe like it's too rich, then it sounds like the EEC is trying to adjust for the lean condition by dumping too much fuel.

Using the bad OX sensor as theory, the back soot at WOT would be explained by the engine loading up with carbon build up (and the cats likely getting very hot and dying if not already dead) when just cruising around as you are in closed loop and the EEC is trying to adjust injector pulse widths to bring the oxy sensors into line. Then you slam WOT which goes into open loop and the oxy sensors are ignored. The EEC uses look-up tables to determine pulse widths so you are running a little better and you blow all the carbon through the exhaust system.

An oxy sensor reading lean all the time should just kill fuel mileage.
 
That's also a classic example of an intake leak after the TB. Under vacuum, the cylinders would be getting more air than the MAF sees (running lean); and under boost, less air (running rich).

I'd check for that first - might be a simple case of a loose connection or a hose that came off.
 
hmm...

It all sounds logical. I do have a check engine light come on also usually when I "get on the gas". But it doesn't say anything about the oxy sensors. Can they be bad and not throw a code then? And the original reason I thought it was running like that was because the MAF sensor voltage was to low and the BAP sensor was bad. So I replaced them with two other ones that I KNOW worked and the car still ran like , still threw the CE light, and sometimes the car even stalls when it just sits idling for more than 5 minutes. It will run perfectly smooth with no indication its going to stall, then it stumbles and stalls. She even hesitates somtimes when i give her guess, but not everytime.

I am however going to check for leaks in the intake system see if theres any. I will try some of yours guy's suggestions. Any other idea's on what my be wrong would be helpful!! thanks for the input so far.

Oh and Mike, I would check fuel economy but I don't know what the car got originally. Its always had this problem since I got it. Should I just assume its around what a normal SC would get even though its modified and what not along with gears?
 
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Like John said, it could be a air leak after the maf as well. You said the codes are saying lean on the left and right banks.

That code will be generated because the EEC is receiving a signal from the oxygen sensors that tells it that #1 - the sensors are not reading out of range, and #2 - the sensors are saying things are lean.

So there are two possible realities. #1 - the sensors are innacurately reporting a lean condition. #2 - You are experiencing a lean condition.

So you're right to check for any leaks.

As far as economy, I'd just check it for a baseline. Report it here and people can judge what's right or not. Since your static displacement is the same as any other SC, it shouldn't be too far off. I.E. 20 mpg might be o.k.. 12mpg would be terrible.
 
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