Has factory ECU and only mods are catless downpipe & chopped airbox w/ K&N installed, no check engine codes stored and drivability/idle are perfect, starts right up warm or cold...

when WOT 5000+rpm it puffs a fair amount of black smoke from being too rich (is DEFINATLEY black and fuel, NOT white/grey/blue)... tends to leave a fair amount of soot on my entire bumper cover as well

anyone had this problem and corrected it before?

 

If you still have the main cat, it sounds like it is dead or dying. The cat should normally oxidize the excess fuel, or overheat trying if the mixture is really too rich.

Or, maybe air flow to the cat has somehow been blocked (malfunctioning ACV or air pump).

 

It also could be an ignition problem causing a "not so efficient" combustion (resulting in excess unburnt fuel).

Things I would check (and in the order I would check them):

1. main cat
2. spark plugs
3. spark plug wires
4. coils

 

plugs have 2k on em (ngk coppers), plug wires are 500 miles old (ngk), have had the cat off and shook it while i did, nothing was rattling around... not sure on the coils, seems like the top end kinda sucks past 6500 but it doesn't fully breakup or cut/stutter so i dunno

airpump functions properly, i can hear it turn on and off (airbox is chopped, i can hear the air pulses), not sure on the ACV or how to check it, but my problems are wot 5000+rpm those shouldn't matter?

 

Sounds like an ignition problem, so It's really odd to hear you have new plugs and wires. Check your grounds and coils.

 

I would pull your plugs and take a look at them. Ive fouled plugs in 2k before. It doesnt hurt to give em a look, it only takes a few minutes.

 

I had a similar problem with black smoke. It went away when I started using better quality gas. Texaco w/techron. I have the exact same mods as you do. Down pipe and modified stock air box. My original engine has 98k on it with the stock cat and muffler. Hell I still even have the original spark plug wires. Right now I got about 12k on the spark plugs and don't get the black smoke. If you do the water decarbonizing method, it will also steam clean out your exhaust and cat. That may help some.

Do you have a boost gauge to make sure the secondary turbo is kicking in? When I first got my car I thought everything was working ok however, I did noticed not as much kick in the upper rpm's (5k and higher). When I hooked up my boost gauge, I saw that the secondary wasn't working. My turbo outlet pipe was loose so I retightened it fixing the problem. Without the secondaries functioning, you will have more unburnt fuel exit out the exhaust.

 

^FWIW.... after procrastinating for a few months, I recently changed out an AIT sensor that had been bad, which had been making my car run pretty rich. But despite new plugs, I had a similar problem at WOT kicking out alot of soot. I did the water injection and it seemed to improve. At least I can't see it through my tinted back window anymore.

 

i alerady sucked a 2 litre through it few weeks ago, how did you know your AIT was bad?

 

CEL (#11)

 

yeah no codes for me, hmm