Hesitation off the line, bad MPG
#17
04-25-2016, 08:54 AM
What year is the truck?
I suspect you have a couple issues, one causing the terrible gas milage and another causing the stumble. Does it stumble when the engine is cold or does that only do that after it reaches operating temp? If this is the case then the computer is commanding a lean fuel mixture for some reason. Possibilities could include a stuck open injector that is dumping too much fuel into 1 cylinder and the computer is running all the others lean trying to compensate. If fuel pressure drops immediately when the pump stops that could indicate a leaking injector, a wet plug in that hole would confirm it.
If the system holds fuel pressure fine then pull the PCM out and look for evidence of leaking capacitors, if there is then consider replacing the PCM, caps can be replaced fairly easily but if the board is damaged from the leaks then there is no point.
I suspect you have a couple issues, one causing the terrible gas milage and another causing the stumble. Does it stumble when the engine is cold or does that only do that after it reaches operating temp? If this is the case then the computer is commanding a lean fuel mixture for some reason. Possibilities could include a stuck open injector that is dumping too much fuel into 1 cylinder and the computer is running all the others lean trying to compensate. If fuel pressure drops immediately when the pump stops that could indicate a leaking injector, a wet plug in that hole would confirm it.
If the system holds fuel pressure fine then pull the PCM out and look for evidence of leaking capacitors, if there is then consider replacing the PCM, caps can be replaced fairly easily but if the board is damaged from the leaks then there is no point.
#18
04-25-2016, 02:19 PM
What year is the truck?
I suspect you have a couple issues, one causing the terrible gas milage and another causing the stumble. Does it stumble when the engine is cold or does that only do that after it reaches operating temp? If this is the case then the computer is commanding a lean fuel mixture for some reason. Possibilities could include a stuck open injector that is dumping too much fuel into 1 cylinder and the computer is running all the others lean trying to compensate. If fuel pressure drops immediately when the pump stops that could indicate a leaking injector, a wet plug in that hole would confirm it.
If the system holds fuel pressure fine then pull the PCM out and look for evidence of leaking capacitors, if there is then consider replacing the PCM, caps can be replaced fairly easily but if the board is damaged from the leaks then there is no point.
I suspect you have a couple issues, one causing the terrible gas milage and another causing the stumble. Does it stumble when the engine is cold or does that only do that after it reaches operating temp? If this is the case then the computer is commanding a lean fuel mixture for some reason. Possibilities could include a stuck open injector that is dumping too much fuel into 1 cylinder and the computer is running all the others lean trying to compensate. If fuel pressure drops immediately when the pump stops that could indicate a leaking injector, a wet plug in that hole would confirm it.
If the system holds fuel pressure fine then pull the PCM out and look for evidence of leaking capacitors, if there is then consider replacing the PCM, caps can be replaced fairly easily but if the board is damaged from the leaks then there is no point.
#19
04-25-2016, 05:20 PM
I might have missed it somewhere in this thread, but have you checked or replaced the throttle position sensor or MAP sensor? A bad TPS can cause the stumble and violent/jerky behavior. Bad MAP sensor can cause poor fuel economy. If I am correct it is a Speed Density type fuel injection. I know the O2 sensor is the main contributor of A/F ratio. But a Speed Density system relies heavily on TPS, MAP, and engine RPM to determine the mass air entering the engine. So correct operation of those sensors are critical. Unlike the Mass Air type fuel injection that measures in mass of incoming air directly.
Bas O2 sensors can also cause poor fuel economy. They typically fail in a lean output signal condition.
Bas O2 sensors can also cause poor fuel economy. They typically fail in a lean output signal condition.
#20
04-25-2016, 07:50 PM
I might have missed it somewhere in this thread, but have you checked or replaced the throttle position sensor or MAP sensor? A bad TPS can cause the stumble and violent/jerky behavior. Bad MAP sensor can cause poor fuel economy. If I am correct it is a Speed Density type fuel injection. I know the O2 sensor is the main contributor of A/F ratio. But a Speed Density system relies heavily on TPS, MAP, and engine RPM to determine the mass air entering the engine. So correct operation of those sensors are critical. Unlike the Mass Air type fuel injection that measures in mass of incoming air directly.
Bas O2 sensors can also cause poor fuel economy. They typically fail in a lean output signal condition.
Bas O2 sensors can also cause poor fuel economy. They typically fail in a lean output signal condition.
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