Significantly Negative LTFT - Out of ideas
#1
07-22-2018, 01:19 PM
Significantly Negative LTFT - Out of ideas
Hey All!
The Background: I have a 97 D1 with 148k miles. While struggling to return it to good operating condition following who knows how many years of previous owner BS, I've replaced or repaired the following...
Plenum gasket, oil pan gasket, water pump/gasket, oil pump gears, cleaned the pickup screen, master brake cylinder, brake booster, idle air control valve, TPS, cleaned the whole intake manifold till it was clean enough to eat off, replaced breather hoses, fuel pressure regulator vac line, cleaned and lubed throttle cable, replaced all 4 O2 sensors, new MAF, new air filter, 8mm plug wires, brand new spark plugs, all new coolant hoses, new fan clutch, new 180 thermostat, new battery, salvage alternator, new AC compressor clutch bearing, new serpentine belt, new heater hoses, ran several tanks of techron through, new fuel filter, and a handful of other routine maintenance/fluids.
The Problem: My fuel trims are all kinds of goofy. I'm showing both banks with LTFT at -19%. While warm and at idle, my STFT is +20-24%, but while accelerating, it smoothly tapers down to 0 or just below. At cruising speed (70mph), STFT is between 0 and +10%. Im showing active data on my O2's (though I did get a catalytic converter output CEL the other day, my cats are prob. shot, what a shocker). My timing advance seems weird, usually between 35 and 45 when warm. I did some pressure tests at the fuel rail and am not sure what to make of the values, turning the fuel pump on, but not starting the car gave 8 PSI (roughly). At idle, I was around 30-33 PSI. After turning the car off, I watched the pressure for 20 or 30 mins and it gradually raised from 30psi to around 42psi. Is this a fuel pressure regulator problem? If I understand correctly, leaky injectors means losing psi over time (unless physics is broken).
After doing many of the repairs listed above, I did get my adaptive values reset, and have since done that again to verify the LTFT was zero'd out, and migrated back down.
I'm honestly not sure where to go from here. I feel like i keep going down the rabbit hole and haven't been able to ever dig back out. Suggestions?
The Background: I have a 97 D1 with 148k miles. While struggling to return it to good operating condition following who knows how many years of previous owner BS, I've replaced or repaired the following...
Plenum gasket, oil pan gasket, water pump/gasket, oil pump gears, cleaned the pickup screen, master brake cylinder, brake booster, idle air control valve, TPS, cleaned the whole intake manifold till it was clean enough to eat off, replaced breather hoses, fuel pressure regulator vac line, cleaned and lubed throttle cable, replaced all 4 O2 sensors, new MAF, new air filter, 8mm plug wires, brand new spark plugs, all new coolant hoses, new fan clutch, new 180 thermostat, new battery, salvage alternator, new AC compressor clutch bearing, new serpentine belt, new heater hoses, ran several tanks of techron through, new fuel filter, and a handful of other routine maintenance/fluids.
The Problem: My fuel trims are all kinds of goofy. I'm showing both banks with LTFT at -19%. While warm and at idle, my STFT is +20-24%, but while accelerating, it smoothly tapers down to 0 or just below. At cruising speed (70mph), STFT is between 0 and +10%. Im showing active data on my O2's (though I did get a catalytic converter output CEL the other day, my cats are prob. shot, what a shocker). My timing advance seems weird, usually between 35 and 45 when warm. I did some pressure tests at the fuel rail and am not sure what to make of the values, turning the fuel pump on, but not starting the car gave 8 PSI (roughly). At idle, I was around 30-33 PSI. After turning the car off, I watched the pressure for 20 or 30 mins and it gradually raised from 30psi to around 42psi. Is this a fuel pressure regulator problem? If I understand correctly, leaky injectors means losing psi over time (unless physics is broken).
After doing many of the repairs listed above, I did get my adaptive values reset, and have since done that again to verify the LTFT was zero'd out, and migrated back down.
I'm honestly not sure where to go from here. I feel like i keep going down the rabbit hole and haven't been able to ever dig back out. Suggestions?
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