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Discussion Starter #1
I've data mined this group for solutions to an all too common problem with 4.6 engines, stalls and rough running engine conditions when in closed loop mode, yet running in open loop the engine is smooth as silk. Most of the discussions end without a solution or with an extreme solution that doesn't seem to match my situation. Mine runs fine with the MAF disconnected, connect the MAF, go into closed loop and constantly stalls and rough idle. Since it runs fine in open loop that suggests to me that there are no fuel, vacuum, IAC, mechanical issues with air or fuel delivery or exhaust. I did change the MAF because my code scanner showed no airflow, new MAF shows airflow, as well as the ECM (because some one posted that the ECM fixed their erratic problem) and it is still broke without giving me a failing code. I compared a printout from 10 years ago I had of all sensor readings to current readings and I don't see any drastically different readings. If the EGR was sticky, a vacuum line damaged, etc. I would expect to see the same stall/rough running in open or closed loop modes. Please help me trouble shoot this one. 1995 LX 4.6, 94,000 miles, original owner, stock with no mods. I have the complete factory service manual. Thanks, Steve, 73 de N2UBP
 

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what do your fuel trims look like?
 

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Discussion Starter #3
Currently I'm on vacation and don't have access to the car. I will post fuel trim, etc. early next week. -Thanks!
 

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Discussion Starter #4
Back from vacation. Plugged the scan tool in. Here are a few frames of data.
Short Term Fuel Trim Bank 2-Sensor 2 seems way out of whack.
Car in Park, just idling. I was sitting in the passengers seat monitoring the scan tool and laptop computer.
Suggestions appreciated.
Thank you all.
Steve


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Number of DTCs stored in this ECU 0
Fuel system 1 statusCL
Fuel System 2 status--
Calculated LOAD Value(%)25.5
Engine Coolant Temperature(¡£C)53
Short Term Fuel Trim -Bank 1(%)-20.3
Long Term Fuel Trim - Bank 1(%)-10.2
Short Term Fuel Trim -Bank 2(%)-20.3
Long Term Fuel Trim - Bank 2(%)-10.9
Engine RPM(rpm) 852
Vehicle Speed Sensor(km/h)0
Ignition Timing Advanece for #1 Cylinder(¡£)22.0
Intake Air Temperature(¡£C)24
Air Flow Rate from Mass Air Flow(g/s)10.33
Absolute Throttle Position(%)18.8
Commanded Secondary Air StatusOFF
Location of Oxygen SensorsB1S12--B2S12--
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.735
Short Term Fuel Trim Bank 1-Sensor 1(%)-21.9
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.050
Short Term Fuel Trim Bank 1-Sensor 2(%)N/A
Oxygen Sensor Output Voltage Bank 2-Sensor 1(V)0.140
Short Term Fuel Trim Bank 2-Sensor 1(%)-20.3
Oxygen Sensor Output Voltage Bank 2-Sensor 2(V)0.050
Short Term Fuel Trim Bank 2-Sensor 2(%)99.2
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Live Data
Number of DTCs stored in this ECU 0
Fuel system 1 statusOL-Fault
Fuel System 2 status--
Calculated LOAD Value(%)23.9
Engine Coolant Temperature(¡£C)62
Short Term Fuel Trim -Bank 1(%)9.4
Long Term Fuel Trim - Bank 1(%)0.0
Short Term Fuel Trim -Bank 2(%)9.4
Long Term Fuel Trim - Bank 2(%)0.0
Engine RPM(rpm) 832
Vehicle Speed Sensor(km/h)0
Ignition Timing Advanece for #1 Cylinder(¡£)22.0
Intake Air Temperature(¡£C)24
Air Flow Rate from Mass Air Flow(g/s)10.33
Absolute Throttle Position(%)18.8
Commanded Secondary Air StatusOFF
Location of Oxygen SensorsB1S12--B2S12--
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)1.000
Short Term Fuel Trim Bank 1-Sensor 1(%)9.4
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.055
Short Term Fuel Trim Bank 1-Sensor 2(%)N/A
Oxygen Sensor Output Voltage Bank 2-Sensor 1(V)1.000
Short Term Fuel Trim Bank 2-Sensor 1(%)9.4
Oxygen Sensor Output Voltage Bank 2-Sensor 2(V)0.060
Short Term Fuel Trim Bank 2-Sensor 2(%)99.2
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Number of DTCs stored in this ECU 0
Fuel system 1 statusOL-Fault
Fuel System 2 status--
Calculated LOAD Value(%)26.7
Engine Coolant Temperature(¡£C)62
Short Term Fuel Trim -Bank 1(%)9.4
Long Term Fuel Trim - Bank 1(%)0.0
Short Term Fuel Trim -Bank 2(%)9.4
Long Term Fuel Trim - Bank 2(%)0.0
Engine RPM(rpm) 820
Vehicle Speed Sensor(km/h)0
Ignition Timing Advanece for #1 Cylinder(¡£)22.0
Intake Air Temperature(¡£C)25
Air Flow Rate from Mass Air Flow(g/s)10.29
Absolute Throttle Position(%)18.8
Commanded Secondary Air StatusOFF
Location of Oxygen SensorsB1S12--B2S12--
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)1.000
Short Term Fuel Trim Bank 1-Sensor 1(%)9.4
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.060
Short Term Fuel Trim Bank 1-Sensor 2(%)N/A
Oxygen Sensor Output Voltage Bank 2-Sensor 1(V)1.000
Short Term Fuel Trim Bank 2-Sensor 1(%)9.4
Oxygen Sensor Output Voltage Bank 2-Sensor 2(V)0.060
Short Term Fuel Trim Bank 2-Sensor 2(%)99.2
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Number of DTCs stored in this ECU 0
Fuel system 1 statusOL-Fault
Fuel System 2 status--
Calculated LOAD Value(%)26.7
Engine Coolant Temperature(¡£C)62
Short Term Fuel Trim -Bank 1(%)9.4
Long Term Fuel Trim - Bank 1(%)0.0
Short Term Fuel Trim -Bank 2(%)9.4
Long Term Fuel Trim - Bank 2(%)0.0
Engine RPM(rpm) 808
Vehicle Speed Sensor(km/h)0
Ignition Timing Advanece for #1 Cylinder(¡£)22.0
Intake Air Temperature(¡£C)25
Air Flow Rate from Mass Air Flow(g/s)10.33
Absolute Throttle Position(%)18.8
Commanded Secondary Air StatusOFF
Location of Oxygen SensorsB1S12--B2S12--
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)1.000
Short Term Fuel Trim Bank 1-Sensor 1(%)8.6
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.060
Short Term Fuel Trim Bank 1-Sensor 2(%)N/A
Oxygen Sensor Output Voltage Bank 2-Sensor 1(V)1.005
Short Term Fuel Trim Bank 2-Sensor 1(%)8.6
Oxygen Sensor Output Voltage Bank 2-Sensor 2(V)0.055
Short Term Fuel Trim Bank 2-Sensor 2(%)99.2
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Discussion Starter #5
Here is a more complete view of fuel trim data. The previous clip didn't tell the complete story.
I think what I am seeing means the air/fuel mix is too rich?

Thanks,

Steve
 

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looking at your fuel trims yes you are running rich. Being as the car improves so much when you unplugged the maf, I personally believe you have an issue with the maf. Does your car warm up? I see an ECT of 62 there. I guess this is right after you started? I hesitate to condemn a new maf, but it is not unheard of to have brand new parts failed out of the box. Not setting any codes, are you sure you dont have a mechanical failure of some kind? Or even faulty o2's?
 

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Discussion Starter #7
The new Delphi MAF seems to be working. The original showed no change in airflow when I pressed down on the accelerator and increased engine RPM. The new MAF responds with increased airflow readings as RPM increases. I took a wild ass guess and also replaced the IAC, resulting in no improvement. I Googled "Fuel system 1 statusOL-Fault" and the one thing that keeps popping up is it could be the result of failure of upstream O2 sensors. I was skeptical of this diagnoses because I recorded voltage changes on the upstream sensors until I received the error "Fuel system 1 statusOL-Fault" and after that point only saw the upstream sensors pegged at almost 1 volt. Not sure if this is a valid reading or if the inexpensive code scanner gives up providing real readings after the "Fuel system 1 statusOL-Fault" is posted. Then I read a suggestion that O2 sensors, at best, have a lifetime of 100,000 miles and my car has 94,000 on the odometer, so maybe this is valid. I had to take a break from working on the Bird to address an issue on my wife's 3ooM. Driving home from vacation on the Mass Pike a work crew dropped a shovel full of wet concrete and gravel on the car from an overpass while we were driving 65mph underneath it. Was not a pretty result. Now that I have her car back from the body shop I can work on my Bird once more. I'm not getting any younger. I'm not the 38 year old guy who bought this T-Bird new in 1995 any longer and pushing 60 years of age. Not sure I want to jack up the car in the garage and contend with removal and replacement of O2 sensors that have been in service for 21 years. I think I'm about ready to take it to a trusted local "professional" but mom & pop shop in town for further work on this problem, unless you guys think replacing 21 year old O2 sensors is a relatively painless process? I'm just thinking of not having a lift and contending with rusty broken stuff and being an old fart. - Thanks for all your help! Steve
 

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Discussion Starter #8
I have an old Harrison code scanner on the shelf that plugs into a laptop computer and will record the O2 sensor voltages along with up to a total of 6 sensors into a CSV file. I think once I finish a brake job on another car in my stable I will plug this device into the Bird and let it record o2 voltages, MAF and rpm readings from a cold start , then convert it to an Excel file and create a graph of the results to post here for everyone's viewing pleasure and suggestions.
-Steve
 

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Discussion Starter #9
Here is a snapshot of O2 sensor voltage from a dead start 3 minutes after a cold start to pull the car into the garage for about 24 minutes. Something does not seem correct with one bank. I'm thinking maybe the o2 sensor is worn out or something else is very wrong on that engine bank and driving it in an abnormal way?
 

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Discussion Starter #10
Found the fix - New Delphi MAF is out of spec

As suggested in a prior message in this thread, the new Delphi MAF I purchased from Rock Auto is not producing the correct voltages based on engine RPM and air intake. Replacing the MAF again corrected the problem. Thank you all. - Steve:grin2:
 
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