When you disconnect the MAF, the computer recognizes the open circuit and runs at predetermined perimeters. If you wouldn't have told me the MAF was already replaced, I would have told you it is most likely the cause.
Are there any diagnostic trouble codes stored in the car's computer. I realize you indicated it doesn't have an OBD2 system. It should have something to retrieve codes.
As far as removing the oil cap, that isn't reliable. Without codes this becomes a test, evaluate, and then determine what needs done. I'm not familiar with this vehicle, but things such as a vacuum leak (as mentioned), engine coolant temp sensor, fuel pressure, idle air control, and so on can cause idle issues.
So, where do we go with this. I guess since the symptoms are indicative to a mass air flow sensor, we need to recheck that component. Since it runs with it disconnected, either it is bad or there is unmetered air getting into the engine. So, I will try my best to explain how to check the MAF. Please understand this is general in nature. I am not familiar with this vehicle.
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1) Turn the ignition off
2) Connect the MAF sensor’s connector.
3) Backprobe the sensor’s signal power wire with a multi meter, and the ground.
4) Secure the vehicle on a flat surface and in park with the parking brake engaged.
5) Start the engine. Have a helper keep it running.
6) Voltage should be aprox 0.5 to 0.7 volts.
7) Tap the MAF sensor lightly while watching the voltage
8) Voltage should remain steady.
9) If the voltage becomes erratic, chances are something is loose in the sensor and needs replaced.
10) Have a helper rev the engine to aprox 2500 RPMs
11) Watch the voltage. It should increase to aprox 1.5 - 3.0
12) If there’s no output response from the sensor, it is most likely bad.
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Let me know if this is something you can do at home or if you have other questions.
Joe
Saturday, February 8th, 2020 AT 8:04 PM
