Rich at idle

[Cobol]

Today after 1 hour cruising on freeway (running vac not boost most of the time), I let the car cool down as usual. I found that my car was running rich at idle, also got black smoke from exhaust (and some smoke dust on my rear bumper). Eventhough I tried to lean my idle at HKS S-AFR, it didn't help at all.

However, when I ran the car back home, my A/F during cruising didn't show any rich at all (around 14.7 all the time). It ran rich only idle. What should be wrong? It's never happen before.

Please check my profile for mods.

 

[3tcpower]

In my history of cars, which isn't much, the dust on the bumper was caused by the vehicle burning oil. That was on a NA vehicle with almost 300,000 miles, but the principle is the same.

Just a thought and I could be way wrong. Is it still making your bumper dirty every time?

 

[abaum565]

Probably FPR overrun with your 255. Either that or check your intake/filter/MAS for some sort of leak causing it to add fuel. Also, How are your fuels trims? You have link so you have access to the link forums with a wealth of knowledge on fuel trim tuning. Also check your global and deadtime incase they have changed, calibrating your MAS is also something to check into (you will run into this when doing fuel trims, adjusting your lower airflow sliders)