Very Rich at Cold Start

Anything about Ford EEC tuning. TwEECer and Moates questions dominate, but there's some SCT and OBD-II knowledge too.

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Very Rich at Cold Start

Post by wickedsnake00 » Wed Apr 17, 2019 1:00 pm

Car is a 2000 Mustang GT, CVAF1 strategy, running a far from stock setup, custom 4V engine, 03 Cobra hardware, FR500 cams, twin 66s, etc...

On cold start it runs stupid rich. I'm talking 10.0 AFR. Way richer than it should based on the cold base fuel table or cold enleanment table; I've tried leaning those out and haven't got any real response. Idle is dialed in perfect when warm (MAF transfer function, ISC neutral idle air, etc...) ISC multiplier has been increased to no avail. Injector timing has been adjusted to match the cams. Once you get out of the cold idle region, either adding RPM/airflow, adding load, or warming up, it's great. But that first minute or two it's way too rich.

Gut feel is that this is probably in the x-tau/fuel puddle model; the engine is thinking more fuel is ending up in the puddle than actually is. I haven't touched those tables yet, so they're still the stock 2V values. I'm curious to dig around and see what the 4V tables in that area are like. Any other ideas what it could be?

Bonus: Anyone know how to ensure that deceleration fuel shutoff (DFSO) is totally shut off? I tried decreasing the maximum load for it to near zero, minimum speed to 45mph, timer to something really long and the ECT for it to 254. Still seems to be enabled and flutters in and out at very light load at constant low speed ~30mph.

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