Hello, I have a 99 yukon SLT , v8 5.7L 4X4.
The car starts first crank, and it drives well. Full power under load, so I know that my fuel pump is good. It responds well with any amount of throttle applied so The fuel delivery seems to be fine. However, Whenever I drive the car for more than 15 minutes, and the engine warms up to full temperature, it starts to stall when I come to a stop, and the RPM's fluctuate constantly from 500 rpm-600rpm. If i hold the gas with 1 foot, and slightly push the pedal to 700rpm, it will idle fine, but If i let go of the petal , the car will likely turn off instantly. It will start back up and drive as long as I manually keep the RPM at around 700(by pressing the gas pedal). Even after the car is fully warmed up, it drives on the freeway fine, with full power, but right when I come to a stop, it turns off, And I think it's due to the low idle, or low air delivery at idle, via throttle body.
Parts I have replaced : New head gasket, had both heads/valves inspected/ polished by machine shop,new Distributor,new TPS,new MAP sensor, engine coolant temp sensor, I cleaned the throttle body and idle air control valve, both are free of carbon. The engine is almost brand new inside out, and the only thing I haven't replaced so far is the throttle body unit itself, and the idle air control valve.
During closed loop when the engine was idling, I connected a scanner and observed the live data.
Readings
TPS : 0%
Spark advance : 16
MAP : 1.1xx
I don't think that the TPS should be reading 0 when the engine is idling, and already in closed loop. Could this be a throttle body problem, As im considering to just buy the whole throttle body, instead of just replacing the idle air control valve and not solving the problem. The throttle body comes with both sensors.
Thank you for your time, Any suggestions would be appreciated .
The car starts first crank, and it drives well. Full power under load, so I know that my fuel pump is good. It responds well with any amount of throttle applied so The fuel delivery seems to be fine. However, Whenever I drive the car for more than 15 minutes, and the engine warms up to full temperature, it starts to stall when I come to a stop, and the RPM's fluctuate constantly from 500 rpm-600rpm. If i hold the gas with 1 foot, and slightly push the pedal to 700rpm, it will idle fine, but If i let go of the petal , the car will likely turn off instantly. It will start back up and drive as long as I manually keep the RPM at around 700(by pressing the gas pedal). Even after the car is fully warmed up, it drives on the freeway fine, with full power, but right when I come to a stop, it turns off, And I think it's due to the low idle, or low air delivery at idle, via throttle body.
Parts I have replaced : New head gasket, had both heads/valves inspected/ polished by machine shop,new Distributor,new TPS,new MAP sensor, engine coolant temp sensor, I cleaned the throttle body and idle air control valve, both are free of carbon. The engine is almost brand new inside out, and the only thing I haven't replaced so far is the throttle body unit itself, and the idle air control valve.
During closed loop when the engine was idling, I connected a scanner and observed the live data.
Readings
TPS : 0%
Spark advance : 16
MAP : 1.1xx
I don't think that the TPS should be reading 0 when the engine is idling, and already in closed loop. Could this be a throttle body problem, As im considering to just buy the whole throttle body, instead of just replacing the idle air control valve and not solving the problem. The throttle body comes with both sensors.
Thank you for your time, Any suggestions would be appreciated .
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