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Open-Cold ?

Posted: Tue Jul 08, 2008 7:17 pm
by tytlyf
I have noticed that the Fuel Status in the Sensor Window will read "Open-Cold" sometimes. When reviewing datalogs i see this Open Cold situation actually interfering with the drivability of the car. :(

At Low Rpms, the Open-Cold disease will drop my idle below 750 and come close to stalling.
At higher Rpms, the Open-Cold disease will interfere with off-throttle coasting as the engine slows. It's obvious when it happens because it feels like someone tapped the throttle.

I have a k20Z1 (06 rsx type-s) with I/IMG/H/E

Any insight into why the car would go into "Open-Cold" will be appreciated.
My kal and DL is attached. AF tuned.

Take a look at the datalog at the 3 min. 22 sec. mark for the Low RPM problem dropping into the 500's..

The higher rpm problem happens at the 3 min, 53 sec mark. Not sure why the AF fluctuates. Looks like the IGN acts up but not sure why.

Posted: Wed Jul 09, 2008 7:35 am
by Hondata
The fuel system status is something reported to scan tools. The Honda ECU is not very precise is reporting open loop conditions - in many cases it reports 'Open-Cold' when it should be 'Open-Driving Conditions'.

You're seeing the ECU is open loop upon overrun. The idle is dipping because the AF is too rich around idle. Look at the short term trim at the 1:30 to 2:00 mark - there is -18.8% short term trim.

Under advanced change the overrun cutoff to a higher value. I think that you need to change the 1875 rpm low cam value from 21 KPa to something higher, but try different values from 15 KPa to 35 KPa and you should get rid of the decel jerk.

Take out the 2% fuel from cylinder #3. That is for B-Series only - the K20 doesn't run lean on #3.