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-25% Fuel trim on decel and start up

Posted: Tue Sep 23, 2014 4:41 am
by Piv
Hello, we had that issue for a while now and the latest update hasn't changed anything.

When you start the car up, the ECU is doing a -25% short trim compensation before working alright, then on deceleration it will do the same thing making the car stalls

Any reasons or way to fix the issue ?

I tried on both 1.9.1 and 1.9.3beta

Re: -25% Fuel trim on decel and start up

Posted: Tue Sep 23, 2014 9:26 am
by Spunkster
Post the calibration and also list everything that has been done with this vehicle.

Re: -25% Fuel trim on decel and start up

Posted: Tue Sep 23, 2014 12:32 pm
by Hondata
The -25% trim is a 'learned fuel value' which is like a short term trim, except it is used after the injectors first re-start.

The value going to -25% indicates that the short term trim is pulling a lot of fuel. You fuel tables need a lot of tuning, or it could be that the o2 sensor is failing.

Re: -25% Fuel trim on decel and start up

Posted: Mon Feb 09, 2015 6:54 am
by Piv
Spunkster wrote:Post the calibration and also list everything that has been done with this vehicle.
The car has a Rotrex C38 81 kit and the usual breathing mods, the O2 sensor seems to work correctly on normal driving and the tuning is good.

While I do understand the indications of a lot of fuel removed by going -25% I know the car isn't running that rich

I would expect the corrections to behave like this before the O2 has warm up enough to work, same goes on deceleration when compensation should be 0%. I tried to get the window of correction narrower but that didn't works too.

Re: -25% Fuel trim on decel and start up

Posted: Mon Feb 09, 2015 11:24 am
by Spunkster
Are you tuning this yourself, or was this tuned by a shop on the dyno?

Re: -25% Fuel trim on decel and start up

Posted: Mon Feb 09, 2015 2:25 pm
by Piv
It was tuned by another shop and brought to me for a tweak, done on a Dynodynamics but the issue became present when the customer updated the firmware on its flashpro a year or so ago before I saw the car for the first time.

Re: -25% Fuel trim on decel and start up

Posted: Sat Feb 21, 2015 2:48 am
by Piv
Hello guys,

Any ideas you would suggest?

Re: -25% Fuel trim on decel and start up

Posted: Mon Feb 23, 2015 10:39 am
by Spunkster
It sounds like it just needs better tuning so that it is not maxing out the trim at startup. You might try starting with a factory calibration and then tune from there instead. Sometimes it takes less time to start over than to try to fix a poorly tuned calibration.

Re: -25% Fuel trim on decel and start up

Posted: Thu Jun 04, 2015 3:32 am
by Piv
For people having the same issues, it ended up being a faulty sensor, replaced it and it fixed the problem :)

Re: -25% Fuel trim on decel and start up

Posted: Sun Jun 14, 2015 4:14 pm
by Hondata
Thanks for posting the resolution.

Re: -25% Fuel trim on decel and start up

Posted: Sat Aug 15, 2015 11:31 am
by andrew87890
what sensor?