I know, I should just floor it everywhere I go... just hard on the driving record. Here is the DL...
- The vehicle starts and revs to 2k RPM, then drops and stumbles severely stalling multiple times until it warms and after many minutes and applications of the throttle then settles on around 1k RPM. It seems like it's too lean at startup. Warmed up and in gear, it drops to 6-700 RPM and gets a rapid idle oscillation. Lots of hesitation at partial throttle with excellent power at full throttle.
- The FMS ECU voltage checks all checked out except for the VS values which reflect the AFM flapper door not opening enough. THW was in range at ambient as well as engine warmed up.
- Initial checks show out of range AFM values in the lean direction (high voltage, flapper door not opening enough) with O2 voltages in the very rich direction (60-75mV). - O2 VF1 and 2 voltages (both are similar) settle in around 60-75mV at 2500RPM . Both old and new AFM's have the same resistances. Both old and new O2 sensors reflected similar voltages. AFM Supply voltage is spot on. . The vehicle exhaust smells rich.
- Manifold vacuum measures good and extensive spraying for vacuum leaks (multiple cans of carb cleaner) reveals no leaks. My engine is looking cleaner.
- Compression is 150psi +/- a few across all 6.
- ISC, AFM, O2 sensors, fuel pressure regulator, and Water temp sensor replaced, all are working and none impacted symptoms when changed. New plugs, cap, rotor, and wires all replaced and did not impact symptoms.
-- Fuel pressure has not been measured, need to get a higher pressure gauge. However, excellent full throttle performance suggests fuel delivery is adequate for full power and so should be for partial throttle loads.
- EGR valve was removed, inspected, operated with a vacuum pump, reinstalled, verified to work (open/close when it should).
- Unplugging both O2 sensors to presumably force the engine open loop causes the idle to drop to around 650RPM but with a rapid oscillation. Plugging them back in, the engine increases the idle back to 1k to 1,100 RPM with some hint of the oscillation.
- Hypothesis 1, air hose leak. Even though it has been thoroughly inspected and sprayed while running showing no signs of leakage it will be replaced tomorrow. Replaced with new, no improvement.
- Hypothesis 2: Undetectable air leak somewhere other than the intake tube downstream of the AFM but upstream of the throttle valve. However, that would typically create a lean condition, the O2 sensors are reading lean (low V) but the truck smells rich suggesting the ECU is overcompensating.
- Hypothesis 3: Bad ECM
- Hypothesis 4: Bad harness possibly ground leakage causing the injectors to over inject.
If I could buy a new harness for an OBD1 1FZE I'd probably just do it but I can't. If the intake tube doesn't do the trick I will look for another ECU.
If anyone has any divine inspiration please share the wisdom.
Frank
- The vehicle starts and revs to 2k RPM, then drops and stumbles severely stalling multiple times until it warms and after many minutes and applications of the throttle then settles on around 1k RPM. It seems like it's too lean at startup. Warmed up and in gear, it drops to 6-700 RPM and gets a rapid idle oscillation. Lots of hesitation at partial throttle with excellent power at full throttle.
- The FMS ECU voltage checks all checked out except for the VS values which reflect the AFM flapper door not opening enough. THW was in range at ambient as well as engine warmed up.
- Initial checks show out of range AFM values in the lean direction (high voltage, flapper door not opening enough) with O2 voltages in the very rich direction (60-75mV). - O2 VF1 and 2 voltages (both are similar) settle in around 60-75mV at 2500RPM . Both old and new AFM's have the same resistances. Both old and new O2 sensors reflected similar voltages. AFM Supply voltage is spot on. . The vehicle exhaust smells rich.
- Manifold vacuum measures good and extensive spraying for vacuum leaks (multiple cans of carb cleaner) reveals no leaks. My engine is looking cleaner.
- Compression is 150psi +/- a few across all 6.
- ISC, AFM, O2 sensors, fuel pressure regulator, and Water temp sensor replaced, all are working and none impacted symptoms when changed. New plugs, cap, rotor, and wires all replaced and did not impact symptoms.
-- Fuel pressure has not been measured, need to get a higher pressure gauge. However, excellent full throttle performance suggests fuel delivery is adequate for full power and so should be for partial throttle loads.
- EGR valve was removed, inspected, operated with a vacuum pump, reinstalled, verified to work (open/close when it should).
- Unplugging both O2 sensors to presumably force the engine open loop causes the idle to drop to around 650RPM but with a rapid oscillation. Plugging them back in, the engine increases the idle back to 1k to 1,100 RPM with some hint of the oscillation.
- Hypothesis 1, air hose leak. Even though it has been thoroughly inspected and sprayed while running showing no signs of leakage it will be replaced tomorrow. Replaced with new, no improvement.
- Hypothesis 2: Undetectable air leak somewhere other than the intake tube downstream of the AFM but upstream of the throttle valve. However, that would typically create a lean condition, the O2 sensors are reading lean (low V) but the truck smells rich suggesting the ECU is overcompensating.
- Hypothesis 3: Bad ECM
- Hypothesis 4: Bad harness possibly ground leakage causing the injectors to over inject.
If I could buy a new harness for an OBD1 1FZE I'd probably just do it but I can't. If the intake tube doesn't do the trick I will look for another ECU.
If anyone has any divine inspiration please share the wisdom.
Frank
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), tightly wrap the intake tube with tape as a temporary way of eliminating or confirming it as an issue.
