Engine Stall and TPS
05-26-2014, 06:52 PM
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Engine Stall and TPS I have spent all day chasing one issue, to find it leads me to another one and another one.....
Here is the situation
8.1L in rockcrawler, maybe 100 hrs on engine since build
Motor started stalling when dropping from speed down into idle
It pulled a DTC for crank position sensor failure so I replaced crank position sensor. It still has the same problem of stalling but has not thrown the DTC all day
Timing goes stupid when dropping to idle and maybe it always has. There was a big difference between the 800 rpm values in my Main Spark Tables and the Idle spark in gear table so I made those match more closely. That has helped, it nearly stalls now.
This got me looking at when the idle table is made active. The tune has this at the stock value of 1.5%. The scan of the TPS never drops below 14%. Why is it never dropping to zero?
The throttle body is mechanically centered to be partially open and in its normal at rest position reads 1.2 volts. If I force it closed it will read .5v
The throttle body was new with the motor build, the old throttle body also has this same partially open at rest condition.
_03 log is before adjusting spark tables, _04 log is after adjusting table
What should I be chasing next? Thanks.
Here is the situation
8.1L in rockcrawler, maybe 100 hrs on engine since build
Motor started stalling when dropping from speed down into idle
It pulled a DTC for crank position sensor failure so I replaced crank position sensor. It still has the same problem of stalling but has not thrown the DTC all day
Timing goes stupid when dropping to idle and maybe it always has. There was a big difference between the 800 rpm values in my Main Spark Tables and the Idle spark in gear table so I made those match more closely. That has helped, it nearly stalls now.
This got me looking at when the idle table is made active. The tune has this at the stock value of 1.5%. The scan of the TPS never drops below 14%. Why is it never dropping to zero?
The throttle body is mechanically centered to be partially open and in its normal at rest position reads 1.2 volts. If I force it closed it will read .5v
The throttle body was new with the motor build, the old throttle body also has this same partially open at rest condition.
_03 log is before adjusting spark tables, _04 log is after adjusting table
What should I be chasing next? Thanks.
