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Check that MAF Plug.. see if that might be the problem..
I’m thinking you should hook up some software, and watch the O2 Sensor Voltages.. My Favorite program for that is ECU Talk, but I think Conzult can do it as well.
With the Engine Warm at High Idle ( ~2k RPM ) the O2 Sensor Voltages should be cycling above and below .45 Volt about every 2 Seconds or so.. Both Left and right.. This indicates the ECU is able to Control the Fuel Mixture, and it’s ‘Fuel Trims’ ( Left Bank and Right Bank ) will either pull or add fuel to the Calculations to get a Stable Oscillation.. This is a ‘Normal Closed Loop Behavior’
If the ECU was having difficulties getting the O2 Sensor Voltage to Cycle, then that would indicate a Leaking Injector, or a Sluggish O2 Sensor.. Or Massive Air leak..
Normal OBD2 Cars will settle into a Stable Idle with the O2 Sensor Voltage still Cycling, and the Ignition Timing, as well as the IAC will do the Trimming to get the Idle Speed proper.. The 300 Does not do that.. The observations I have of the 300 at Idle are.. It will Lock the Ignition Timing at 15 Deg, and try and find a Very lean Mixture to Idle at, and use the IAC to control Idle Speed.. The Early 300’s will open the Air Injection at Idle to put more Air into the Cats to Burn the Hc’s at idle.. the Later 300’s do not have the Air Injection System, but the Idle performs the same..
In actually, when the 300 comes to Idle from speed, it will take the O2 Sensor voltage from a Nice Smooth Cycling, and let it go Rich.. then it will slowly pull the Mixture Lean ( O2 Sensor Voltage will go Below .45 Volt ) and then it will usually stay below .45 and about every 4-5 minutes it will bump up into the .6-.8 Volt range then settle back down..
From a Smog perspective this is Terrible, as the Lean Mixture will remove the Fuel from the Cat, and let the Fire go Out, and it cools down.. But that is a Different Soap Box..
I’d like you to hook up some software to the 300.. and check the O2 Sensor Voltages when warm, and see what your Cycling Time Frame is.. then let the Car Idle and see where the O2 Sensor Voltage goes.. If you are having a lean stumble at idle, the O2 Sensor voltage will drop below .2 Volt, and not go into the .45 range at all.. and Conversely, if you are having a Rich Idle problem, the O2 Sensor Voltage will stay above .5-.6 and never get to the .45 Volt range.. Please Post what you find.. Cj
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01:54:26 08/25/20
