The Motorist's Pride
The four stroke engine cycle is a precise sequence of intake compression power and exhaust strokes that transforms fuel combustion into mechanical rotation. During the intake stroke the piston moves downward creating vacuum that draws in the air fuel mixture. The compression stroke then squeezes this mixture to increase combustion efficiency. The power stroke ignites the compressed mixture causing rapid expansion that forces the piston downward generating torque. Finally the exhaust stroke pushes out burned gases through the open exhaust valve completing the cycle. This continuous loop of suction squeeze bang and blow is the fundamental process behind nearly every internal combustion engine on the road.
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My 2011 Jaguar fault code P0105 tells me my MAP sensor is playing up, Have replaced sensor with genuine part, have since found out that my Barometric reading is at odds with my map sensor . The car ecm reads Baro pressure at ignition stage 1 then once started the MAP sensor takes over, (I think) The ECU Baro pressure reads 199kpa?? How can I change the Baro back to the 99kpa it should read. Many Thanks
Seeing a barometric pressure reading of 199 kPa on a 2011 Jaguar at ignition-on is a red flag, this value is physically impossible under normal atmospheric conditions.
At sea level, you’re looking at roughly 100 to 102 kPa, and even at the bottom of the Dead Sea (the lowest point on Earth), it doesn’t exceed 108 kPa. So, 199 kPa suggests either a serious sensor input error or a corruption in the ECU’s interpretation of the signal. On Jags of this era, the ECU performs a barometric pressure snap shot during key on before engine start, using the MAP sensor as the measuring device since there’s no separate BARO sensor. If the intake manifold or MAP port is contaminated, restricted, or sees abnormal pressure (like a stuck open EGR or boost control issue), it can skew this reading.
Yes, a faulty O2 sensor can cause this issue. It helps regulate the air-fuel mixture. If it's not working properly in cold conditions, the engine may run too rich or lean, resulting in rough idling and vibrations.
If it’s the O2 sensor, why would it only happen when the engine is cold? Wouldn’t it affect performance all the time?