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closed loop over correcting?


yoda598
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hey guys, im having an issue on start up where the car will idle perfectly at 14.7-14.8 on the wideband but when closed loop kicks in it shoots to rich!! like 10.0+rich, you can watch the ltft and stft start adding fuel. but if you drive before it does it (30 seconds maybe) its fine. when you stop and check fuel trims the theyre perfect. maybe 1% or so at idle. its driving me mad!!!

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Is the sensor dead?

Is your injector trims within 3% when warm at cruise and idle?

Do you have a large dump pipe?

Assuming the sensor isn't dead and you have an aftermarket dump pipe this is not uncommon. A simple work around is to increase the closed loop delay when cold to 2 minutes.

This assumes your injector scalars are within a few percent when warm, injector scaling that is up the creek will do things like this as well.

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16 minutes ago, Roland@pcmtec said:

Is the sensor dead?

Is your injector trims within 3% when warm at cruise and idle?

Do you have a large dump pipe?

Assuming the sensor isn't dead and you have an aftermarket dump pipe this is not uncommon. A simple work around is to increase the closed loop delay when cold to 2 minutes.

This assumes your injector scalars are within a few percent when warm, injector scaling that is up the creek will do things like this as well.

I do have a 4" dump! Sensor seems good, not too old as far as I know. I'll replace it soon just incase. Injector trims are pretty spot on. I'll give it a go and let you know the outcome. 

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I've had this exact issue with the trims intermittently adding fuel at startup and also the needing to rev or drive it after it started, to fix the issue.

Turns out I had melted narrow band wiring from a 4 inch dump install. I did replace the NB sensor with another second hand unit as part of the diagnosing process so that may have had something to do with it.

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