Weird fuel trim problem

TurboTPI

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So my car (2001 Regal GS) has this really strange issue. It runs extremely rich during light load driving for the first 5 mins of driving. It will be between 10:1 - 12:1 unless i accelerate at like 25% throttle or more. It is in closed loop when it does this. Long term fuel trims will be 10% or more, short term trims will be in positive also and o2 voltage will be around 900mV. So the ecm knows its unning rich but it keeps adding fuel. Then after about 5min, its straightens out and fuel trims go to + - 5% like normal and a/f ratio is normal up and down between 14:1 - 15.5:1. Its not in open loop during this issue, its in cosed loop. And if i turn the car off and start it back up right away, it will do it again for another 5min about. Anyone ever seen anything like that before?
 

GTPpower

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Did you remove the cat? Sounds like it's doing the cat test to me.
 

TurboTPI

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i have a high flow cat, but i have all the rear o2 codes turned off and dont even have the rear o2 plugged in. Can that cause my issue?
 

b4black

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I'd second the cat test. Try plugging the rear sensor in. The quicker the test pass or fails, the sooner it is done. I had a dead sensor (set to not report a MIL) and the test just kept running and running. Drove me nuts until I installed a new sensor.
 

GTPpower

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Yeah, put the sensor back in and see if you notice a difference.
 

Turbocharged400sbc

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its 6 passes or 6 fails before the cat test state is put into the OBD2 readiness monitors as pass/fail

in tiny youll find the cat test can run up to 16 times per drive....without setting it to 0 all datalog data is questionable although larger datalogs mitigate the effects somewhat.

setting to not enabled is a workaround but needs to be enabled/not reported to do what needs done....if ya know what i mean....every year/2 years
 

boostedguy05

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And like our own 3800 batman, when needed, James comes out of the shadows to help those in need.
 

TurboTPI

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Thanks guys. Ill put the sensor back in and see what happens. All my EVAP stuff is still on and functioning, so that shouldnt be part of the problem.
 

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