Not running right -- smoking under hard acceleration

[cjman15]

my car will run normal and smoke free when i keep it under about 2500-3000 rpm, but once i drop the throttle a little harder and let it wind up some more, i get a pretty steady dark smoke... it's not very heavy or ploomy, just smells and its pretty noticable... i know this is common... what should i check?

 

[90mustangGT]

Piston ring blowbye, wore out piston rings.

 

[Fink]

Could be Valve seals

 

[I_AM_CANADIAN]

I thought that when you go open throttle, the O2 sensor "shuts off" and the injectors just blast fuel, causing a rich condition, which then causes back smoke?

 

[cjman15]

my car has run rich ever since i got it... and i have no cats... so that might have something to do with it

 

[HISSIN50]

I thought that when you go open throttle, the O2 sensor "shuts off" and the injectors just blast fuel, causing a rich condition, which then causes back smoke?

on foxes, the puter ignores input from the O2's (they still do function at WOT). there is still some fuel trimming going on though. it is on the rich side (vs the SN EEC-IV puters).

 

[I_AM_CANADIAN]

on foxes, the puter ignores input from the O2's (they still do function at WOT). there is still some fuel trimming going on though. it is on the rich side (vs the SN EEC-IV puters).

so then it is normal for some black smoke when under hard accel?

 

[cjman15]

i'm not at WOT when it smokes, it'll do it with like 1/2 to 3/4 throttle above 3k-3.5k rpm

 

[HISSIN50]

so then it is normal for some black smoke when under hard accel?

you are correct - it can be normal (relatively speaking). the fuel trim is on the rich side (which is nice. the T4MO puter on the SN's trim a good bit at WOT, which kinda sucks).