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Hello everyone.
I need some help diagnosing my car issues using fuel trims data and MAP data.
Hope you can advice.
Car is a :
Year 2011 Daihatsu Sirion.
4 cylinder engine code K3-VE. Its 1.3 liter engine.
Automatic transmission.
The car uses OBD2.
Car uses only MAP and IAT sensor. Also uses Narrowband upstream and downstream O2 sensor.
NO Check Engine Light and Scan shows NO DTC.
In the beginning the LTFT was at 45-50%. After using Brakeparts Cleaner, I found many vacuum hoses (evap,pcv,brake booster) to be brittle and broken, even the PCV valve grommet was leaking. not to mention the intake manifold gasket as well. Had ALL of them replaced and now LTFT is down to around 27%.
BUT if I raise the rpms when driving LTFT drops to 7.8% and stays there. So there still is a vacuum leak somewhere. I suspect the injector bush/grommet.
BUT something baffles me, my MAP sensor seems to understate when the car is in Neutral or Park. At N or P gear and at Idle it reads 29kPA or 8.9inHg. And thus the STFT fuel trims rises to +20-25% to compensate for the lack of fuel.
And no matter how much I rev the engine MAP pressure drops to 25kPA/7.3inHg and stays there in these higher rpms. Release the throttle and it goes back up to 29kPa... shouldnt it go up with higher revs?
BUT here's the thing, with D gear engaged ,car stationary the MAP reads higher at 39-40kPa or 11inHg. And when the car's being driven , the MAP pressure behaves normally, as in if I throttle down the MAP fluctuates between 40-90kPa depending how hard I throttle it. But once back in Neutral or Park gear, the MAP goes back to 29kPa and stays at 25kPa when revved.
Why is the MAP seem to be behaving like this? Seems to work properly when engaged in gear but wrongly in Neutral gear. What could be wrong?
Im trying fix this but also want to understand whats happening.
MAP sensor shows engine load - if you floored it then it would go to 100kpa [or whatever the current barometric pressure is] for a fraction of a second.
In Park and neutral load is at its lowest but when you put it in drive the engine is pulling against the transmission, so the kpa increases [increase in load]
Getting involved in discussions because I have a lot to learn still.
