This topic contains 1 reply, has 2 voices, and was last updated by 
Rahul Jones 5 months ago.
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Topic
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Hello guys,
im having trims set as at 25% because of something going bad in my car. It always happen after few minutes drive. Im already in closed loop when it occures. My downstream sensor goes flat to 0v and will never recover. My upstream will stop oscillating (only few bumps from 0 to 0.5v) a moment after and my trims will go to 25% as soon as i accelerate. So i guess the upstream behaviour is normal as it’s not communicating anymore with ECU. After few drive, a P0170 code will occure, related to powertrain/ trim malfunction but i guess it’s because of the 25% trims that this code is thrown ? Then I had rough idle sometimes but not always.
Here is the work i did to find the fault : fuel filter, air filter, head clutch gasket, air intake gasket, exhaust manifold gasket, swapping maf (readings are normal on both), spark plugs, cleaning egr (switch correctly), cleaning injectors (ultrasonic bath and underpressure cleaning), cleaning throttle body, ignition coil test with opcom…
Im wondering if my cat is bad, as im not getting P0420 code, its a bit strange.
If you guys have any advices, i will take them obviously to end this nightmare.
cheers
Debi
car : Opel Corsa C 2005, 1.2, 80ch, 130km
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Replies
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If it was a cat failure, that should set a code with the high positive fuel trims. I would suspect something like a vacuum leak or anything causing the MAF sensor not to read the air flow. Is it possible for you to screenshot live data of MAF, TPS, MAP, etc sensor readings on idle here? Is your air intake pipe in good condition? Check the additional fittings like hose going to the crankcase, check if the fitting is loose.
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