-
Closed loop fuel trims
I have been doing some logging on my 92 TT. I am using Greg E's setup file on EvoScan 2.9. I have noticed that my front bank fuel trims are all pegged at -25% except for the low whichs will read about -24.5%. The front bank IDC's are about 12+%.
The rear bank looks perfect, all fuel trims are +/- 4.5% and the IDC's are like 2-3% at idle.
Both O2s are new and cycle as the should and there are no major vacuum/boost leaks that I can find.
When in open loop, the IDC's match nicely from front to rear. I have always felt that this car transitions a little odd from closed loop to open.
Any ideas out there on what is going on?
The car also starts weird when warm, sometimes it almost binds like the timing is way advanced, other times it takes a bit of cranking to start and it will start at a low RPM and then come into it. It has very good power under boost, but has always felt a little off in closed loop.
Only mods are...
14 psi
Hotwired stock fuel pump
M2 exhaust
EGR delete
Vac reduction
Cone air filter
No cats at all
Thanks in advance for any help.
-
-
They were perfect when I timed it last winter, I will check again to be sure.
-
When was last time injectors serviced? Can switch banks to see if it makes difference.
Revel in your time
-
I havent serviced the injectors. I would rather not pull the plenum to switch banks. I plan on getting bigger injectors soon, I was just hoping maybe someone has seen this problem before, its an odd one.
-
I leaking injector would ruin the fuel trims and cause poor starting..
Pull the plugs and check the colours, if 1 is darker than the rest that's the problem cylinder.
-
I will dig into it tomorrow.
-
Small update. Today I disconnected the battery for awhile and then logged without even starting the car. The rear O2 was reading zero and so were the trims but the front O2 was showing like 0.064 volts and the trims started low and slowly climbed towards -25. The IDC's for the rear were zero but the front was about 10% and was climbing up to mid 20s by the time I stopped logging.(car still not even running)
So clearly the ECU is seeing a voltage on the front O2 when it shouldnt and is adjusting the trims and IDCs. Now I need to figure out why the ECU see's this voltage. I will start by unplugging the front O2 and see what happens, I expect to see the voltage still present meaning there is something wrong with the ECU.
-
You lost me with IDC...? Injector duty cycle is irrelevant with the engine off. 100% of zero is still zero.
If you clear the KAM, and turn the key on, the fuel trims start at zero and begin moving even with the engine off? One side goes high, the other goes low?
Is this STFT that is moving? or both STFT and LTFT?
-
Your trims should not move with key on engine off and you should deffinitely not see any IDC's recorded!.