Question about 1996 Pontiac Sunfire
Manifold absolute pressure would not affect the transmission. It measures air flow and send the to he ECM (engine control module). Check the fluid level in the transmission. You may also have a plugged filter in the transmission and this will tend the keep the transmission in low gear because the sensor is not getting enough pressure to switch gears. In which case do a filter, gasket and fluid change.
Posted on Apr 23, 2013
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Posted on Jan 02, 2017
This sounds like a fuel issue to me. If I am not mistaken, this engine has two injectors running on a separate fuses. Remove the air cleaner assembly, and make sure both are firing while engine is running. If so, then check the fuel pressure. If you have a fuel pressure gauge, connect it to the fuel rail, and start it up. Remove the vacuum line from the fuel pressure regulator to see where it is set. You should have at least 36lbs of fuel pressure. If the pressure is too low, check the fuel filter. It may be clogged, or you might have a weak fuel pump.
Also you changed the throttle position sensor, you will need to make sure it is set properly.
hope this helps,
Posted on Mar 24, 2009
You could change the fluid and add a good conditioner like lucas, but even if it works better, you are only buying time. Unit is likely beginning to wear out.
Posted on Apr 15, 2009
You can clean the EGR. No promise it will work. I have an idle problem on my `97 Grand Am Se. Shop told me I could clean it and it might solve my problem.
Just remove the EGR with the 2 bolts from the top of the manifold behind the throttle body if you have a 3.4 v6 like I do. Then leave it upside down with throttle body cleaner in it. Fill the EGR level with cleaner and let it soak for at least 30 min or more. Then reinstall.
This will remove any carbon on the inside which plugs the needle from pushing out at highway speeds. Hope this helps. If the problem returns in a week or so then replace with new EGR. New EGR is about $100-200! Cleaning seems to have helped my car did that about 3 weeks ago.
If you have a service engine light on turn the key to the run position on the ignition, pull the fuse to the ECM (batt) and disconnect the wire harness to the EGR. Reinstall it after a 1 min, That will clear all the codes in the ECM and reset everything.
Once you place the ECM fuse back in, start the car. It may stall but let it, DO NOT TOUCH ANY THING. The ECM need to relearn the EGR and engine from all it's sensors like the first time it was started. Just start it up again and it should be like the day it came off the assembly line and will relearn everything.
Good luck and just drive it like you always. If you decide to change the EGR valve, you still need to clear the ECM as mentioned above for the ECM to relearn the new EGR valve. Hope this helps and keep me posted.
Posted on May 25, 2009
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Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance
What does that mean? The Powertrain Control Module (PCM) uses the Manifold Absolute Pressure Sensor (MAP) to monitor engine load. (NOTE: Some vehicles have a Barometric Pressure (BARO) sensor that is integral to the Mass Air Flow (MAF) sensor and do not have a MAP sensor. Other vehicles have a MAF/BARO and a redundant MAP sensor where the MAP sensor functions as a backup input in case of MAF failure.) The PCM supplies a 5 Volt reference signal to the MAP sensor. Usually the PCM also supplies a ground circuit to the MAP sensor as well. As the manifold pressure changes with load, the MAP sensor input informs the PCM. At idle the voltage should be 1 to 1.5 Volts and approximately 4.5 Volts at Wide Open Throttle (WOT). The PCM looks for any change in manifold pressure to be preceded by a change in engine load in the form of changes in throttle angle, engine speed, or Exhaust Gas Recirculation (EGR) flow. If the PCM doesn't see any of these factors change while detecting a rapid change in MAP value, it will set a P0106.
Causes A P0106 could be caused by:
Coolant Thermostat (Coolant Temperature Below Thermostat Regulating
What does that mean? This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat. Similar codes: P0125
In determining the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.
Causes A code P0128 may mean that one or more of the following has happened:
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Manifold Absolute Pressure (MAP) sensor measures the changes in the intake manifold pressure which result from engine load and speed changes, and converts this measurement into a voltage output.
A closed throttle on when the engine is decelerating would produce a relatively low MAP output, while a wide open throttle would produce a high output. Manifold absolute pressure is the opposite of what you would measure on a vacuum gage. When manifold pressure is high, vacuum is low. The MAP sensor is also used to measure barometric pressure under certain conditions, which allows the PCM to automatically adjust for different altitudes.
The PCM sends a 5 volt reference signal to the MAP sensor. As the manifold pressure changes, the electrical resistance of the sensor also changes. By monitoring the sensor output voltage, the PCM can determine the manifold pressure. A higher pressure, low vacuum (high voltage) requires more fuel, while a lower pressure, higher vacuum (low voltage) requires less fuel.
A high or low voltage fault in the MAP sensor circuit should set a DTC P0107 or DTC P0108. If the MAP sensor sends an intermittent zero voltage signal to the PCM, a DTC P0106 will set.
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