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The car is an 02 wrx Au spec, it shows up to be mid 11's AFR at idle, fuel trim says -25% and still rich, bring the rpm up to 1500 and trims drop to -5% average and holds 14.7:1, just on idle it is very rich and throws a CEL for rich on right bank (front)

I have tried removing the Reg hose from vacuum and it does go a little richer, also tried to put 14psi to the reg at idle and goes richer again, so i would say the reg is working fine.

I tried another rear O2 sensor and it is the same.

The injectors are std, If i flash it and say it has 500's injectors it still drops back to full trim and rich idle.

I can remove the AFM from the air stream and keep it pluged in so no air is running through it, and on the DD it then gets AFR up to control it to 14.7:1.


Engine is fine, comps are fine, no miss fire, idle is smooth, I have put a wide band sensor in the dump pipe and yes it is still mid 11's, trim on the road is fine, just rich idle.

No other CEL issues are recorded, all sensors look ok, coolant, AT, idle, tumblers, EGT, IT.

I am at a loss what could cause it to go so rich just on idle.

anyone with any help?

thanks

If you mistakeningly set your injector latency too high it could cause that. Can you open a stock rom next to yours in the editor and copy and paste the injector latency values and reflash?

How does your battery voltage look? Perhaps the ECU is not getting the correct battery voltage as that affects latency.

That is odd behavior. A leak is more likely to cause you to go lean at idle rather than rich.

Could be bad injector(s) or FPR as well, though they don't seem to fail often.

If the injector latency was too high it would reduce fuel thinking they are bigger than they are, I have tried to go to 500 and it still has the same issues, (std is 420) it returns to idle at 14.2 ish, then starts to trim and as it trims it goes rich. If i have a map that is overal too rich taking the number up is the same as triming the full map, just need to log colse loop corection to make sure it is in range, the ecu can trim +/- 25%, thei runs at +2-5% on cruise.

I have an idea that the spark plugs are not firing at idle enough, unburnt fuel will come up as rich, leans it out and then the plugs find it harder to fire, catch 22, will try and new set of plugs and see what that does.

Injector latency is just added to pulse width. Setting it too high will add fuel. It will be a larger difference in lambda or AFR at low injector pulse since the dead time would be a larger percent of total pulse width. So it affect fuel trim the most at the lowest load and idle. 500 is not an injector latency value. That's injector size. Two different things. Not saying that is your problem, but it matches your symptoms.

You may actually see lean spikes if you have misfire, not rich. Idling super rich could be causing your plugs to foul, but I don't think that explains your problem with regards to fueling.

yeah my bad, was think size, the latency is std compared to other known maps.

plugs did not fix it, but 1&3 were a little built up with carbon, might be injector dribling?

Carbon? There shouldn't be any carbon on them at all. They should be very clean.