Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec Finishing up 3L, o2 questions

Todd, Are you running an aftermarket or larger throttlebody?

Also, if you are running the stock 2.5L pcm but using the 3L TB that came on your 3L manifold then you are basically running a larger TB than it is set with.

If you get a chance take a look at MapofTazi's Pro Racer setup and you'll see that there are about 20 things you can do to calibrate your pcm for the 3L engine such as airflow, displacement, intake manifold capacity, dashpot settings, and of course setttings for the IAC valve duty cycle at each rpm in tables.

But assuming you have no vacuum leaks and assuming you are using the stock 2.5L MAF and injectors, then I'd say it is the increase in displacement, different IAC (than the 2.5L IAC the pcm is expecting).