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david craig
david craig, Auto Mechanic
Category: Ford
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Experience:  owner/mechanic at 3D Automotive
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2006 Ford Mustang 4.0L Vehicle has a rough and surging idle

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2006 Ford Mustang 4.0L
Vehicle has a rough and surging idle that fluctuates between 450-700 rpm. CEL with code P0106 (MAP). Would changing the EGR valve be the most likely solution for this situation, being that the MAP is an integrated part of the EGR Valve?
A little history: Vehicle had a misfire in cylinder 1 and would loose power when pressing the accelerator. The Plugs were toast, literally black (because the owner haven't had them changed in forever). So I replaced the plugs, wires, and air filter. That solved the misfire, however the vehicle still idles with the rough surging issue and the P0106. The Live data reveals that the TPS, and pedals responds to input. I noticed that the fuel pressure is about 65psi during the condition. I've read that on this vehicle, the MAP sensor is what the ECM uses to determine fuel pressures and other things. (don't know how true that is) but if that is the case, would replacing the EGR valve/MAP sensor fix my issue?

Hi Im David. allow me a moment to look up some info for you. thanks

Customer: replied 3 months ago.
VIN: 1ZVFT84N365127596

thank you

before you go replacing things. clean the throttle plate, remove the egr valve and clean it out really good. remove the iac and clean it out really good also. do a back pressure test to see if the cats may be partially clogged.

Customer: replied 3 months ago.
Ok. I did disconnect the battery and then cleaned the throttle plate, as well as removed the MAF, and cleaned it too. The throttle body wasn't too bad, but cleaned it anyway. How would I do the back pressure test?

if you dont have a back pressure gauge, you can use a digital temp gun and check the inlet and outlet temp of each cat.

Customer: replied 3 months ago.
I don't have a back pressure gauge, but I do have a digital temp gun. I would assume that if a CAT is clogged, it would be extremely high temp before and at CAT and significantly cooler after cat. If that correct?

no. the outlet of the cat should be at LEAST 100 degrees hotter than the inlet. remember to point the gun at the welds on the cat.

Customer: replied 3 months ago.
Ok. So just for clarification, the outlet of the cat should be at LEAST 100 degrees hotter than the inlet.....is this for a good working CAT or a faulty.

thats for a good working cat

i know it sounds like it should be opposite but the metal and gases inside the cat get unbelievably hot.

Customer: replied 3 months ago.
I can understand that. I'm assuming the gases and the metals chemical combination makes the cat hotter which means that the cat is working and breaking down the bad gases.

you got it

Customer: replied 3 months ago.
Hey David. So I first took out both of the rear O2 sensors and used a hanger to probe inside cats. Bank 1(passenger side) I was able to put the hanger about 6-8 inches in cat. And bank 2 I felt the cone Immediately so wasn't able to put hanger in more than an inch or 2. I'm assuming bank 1 is gone due to the misfire on that side. So I put O2 sensors back and took off egr valve. It had black suit but not hard carbon. But I cleaned it anyway and made sure the valve moved inside without any problems. I started vehicle and let get to operating temp and measured temp before and after cats. At some points I was getting about the same temp before and after. Then other times I was getting about a 70-100 degree Celsius difference. But the highest difference was maybe 105 degree Celsius. I monitored live data and pressed accelerator and the pedal response seemed normal but the tps percentage barely fluctuated regardless how far I depressed pedal. I also monitored map which when the car runs great at idle was about 27.5 to 29.8 in mercury. After I press pedal and car starts to do the funky idle, map would decrease to 14-16.5 in mercury. The barometric pressure stayed at 27.5. also I noticed that at initial startup after cleaning egr and maf, the fuel pressure was between 36-40 psi, but after rough idle happens, the pressure increased to 60-62psi. Also the weird noise that sounds like an intense version of a collapsed straw that is being sucked thru is constantly fluctuating from the egr valve. The P0106 comes up eventually as well. Another weird thing is that is sounds like air through a wind tunnel coming from the exhaust pipe and the temp at the exhaust pipe was between 240-260 degrees Celsius. I know this is a lot of info, and thanks in advance for your patience.

the tps percentage is a problem. i would test that individually before replacing to make sure its not the wiring. but i believe the bank 1 cat needs replaced for sure. everything else seems normal.

Customer: replied 2 months ago.
Is there a way I can actually test the tps? Is there a schematic? I know the throttle body unit is electronic but the tps is a separate part attached to the unit. How would I distinguish which is faulty

standby

having trouble finding one, but i know i have it

Electronic Throttle Body (ETB) The ETB has the following characteristics: 1. The throttle actuator control (TAC) motor is a DC motor controlled by the PCM (requires 2-wires). The gear ratio from the motor to the throttle plate shaft is 17:1. 2. There are 2 designs: parallel and in-series. The parallel design has the motor under the bore parallel 2007 PCED On Board Diagnostics SECTION 1: Description and Operation Procedure revision date: 03/29/2006 to the plate shaft. The motor housing is integrated into the main housing. The in-series design has a separate motor housing. 3. Two springs are used: one is used to close the throttle (main spring) and the other is in a plunger assembly that results in a default angle when no power is applied. This is for limp home reasons (the force of the plunger spring is 2 times stronger than the main spring). The default angle is usually set to result in a top vehicle speed of 48 km/h (30 mph). Typically this throttle angle is 7 to 8 degrees from the hard-stop angle. 4. The closed throttle plate hard stop is used to prevent the throttle from binding in the bore (~0.75 degree). This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle. 5. Unlike cable operated throttle bodies, the intent for the ETB is not to have a hole in the throttle plate or to use plate sealant. The hole is not required in the ETB because the required idle airflow is provided by the plate angle in the throttle body assembly. This plate angle controls idle, idle quality, and eliminates the need for an IAC valve. 6. The TP sensor has 2 signal circuits in the sensor for redundancy. The redundant throttle position signals are required for increased monitoring reasons. The first TP signal (TP1) has a negative slope (increasing angle, decreasing voltage) and the second signal (TP2) has a positive slope (increasing angle, increasing voltage). During normal operation the negative slope TP signal (TP1) is used by the control strategy as the indication of throttle position. The TP sensor assembly requires 4 circuits.  5-volt reference voltage  Signal return (ground)  TP1 voltage with negative voltage slope (5-0 volts)  TP2 voltage with positive voltage slope (0-5 volts) Accelerator Pedal Position (APP) Sensors The ETC strategy uses pedal position sensors as an input to determine the driver demand. 1. There are 3 pedal position signals required for system monitoring. APP1 has a negative slope (increasing angle, decreasing voltage) and APP2 and APP3 both have a positive slope (increasing angle, increasing voltage). During normal operation APP1 is used as the indication of pedal position by the strategy. 2. There are 2 VREF circuits, 2 signal return circuits, and 3 signal circuits (a total of 7 circuits and pins) between the PCM and the APP sensor assembly.  2 reference voltage circuits (5 volts)  2 signal return (ground) circuits  APP1 voltage with negative voltage slope (5-0 volts)  APP2 voltage with positive voltage slope (0-5 volts)  APP3 voltage with positive voltage slope (0-5 volts) 3. The pedal position signal is converted to pedal travel degrees (rotary angle) by the PCM. The software then converts these degrees to counts, which is the input to the torque based strategy. 4. The 3 pedal position signals make sure the PCM receives a correct input even if 1 signal has a concern. The PCM determines if a signal is incorrect by calculating where it should be, inferred from the other signals. A value is substituted for an incorrect signal if 2 of the 3 signals are incorrect. Electronic Throttle Body (ETB) and Accelerator Pedal Assembly Electronic Throttle Control (ETC) System Strategy The torque based ETC strategy was developed to improve fuel economy and to accommodate variable camshaft timing (VCT). This is possible by not coupling the throttle angle to the driver pedal position. Uncoupling the throttle angle (produce engine torque) from the pedal position (driver demand) allows the powertrain control strategy to optimize fuel control and transmission shift schedules while delivering the requested wheel torque. The ETC monitor system is distributed across 2 processors within the PCM: the main powertrain control processor unit (CPU) and a monitoring processor called an enhanced-quizzer (E-Quizzer) processor. The primary monitoring function is carried out by the independent plausibility check (IPC) software, which resides on the main processor.

Electronic Throttle Body (ETB) The ETB has the following characteristics: 1. The throttle actuator control (TAC) motor is a DC motor controlled by the PCM (requires 2-wires). The gear ratio from the motor to the throttle plate shaft is 17:1. 2. There are 2 designs: parallel and in-series. The parallel design has the motor under the bore parallel 2007 PCED On Board Diagnostics SECTION 1: Description and Operation Procedure revision date: 03/29/2006 to the plate shaft. The motor housing is integrated into the main housing. The in-series design has a separate motor housing. 3. Two springs are used: one is used to close the throttle (main spring) and the other is in a plunger assembly that results in a default angle when no power is applied. This is for limp home reasons (the force of the plunger spring is 2 times stronger than the main spring). The default angle is usually set to result in a top vehicle speed of 48 km/h (30 mph). Typically this throttle angle is 7 to 8 degrees from the hard-stop angle. 4. The closed throttle plate hard stop is used to prevent the throttle from binding in the bore (~0.75 degree). This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle. 5. Unlike cable operated throttle bodies, the intent for the ETB is not to have a hole in the throttle plate or to use plate sealant. The hole is not required in the ETB because the required idle airflow is provided by the plate angle in the throttle body assembly. This plate angle controls idle, idle quality, and eliminates the need for an IAC valve. 6. The TP sensor has 2 signal circuits in the sensor for redundancy. The redundant throttle position signals are required for increased monitoring reasons. The first TP signal (TP1) has a negative slope (increasing angle, decreasing voltage) and the second signal (TP2) has a positive slope (increasing angle, increasing voltage). During normal operation the negative slope TP signal (TP1) is used by the control strategy as the indication of throttle position. The TP sensor assembly requires 4 circuits.  5-volt reference voltage  Signal return (ground)  TP1 voltage with negative voltage slope (5-0 volts)  TP2 voltage with positive voltage slope (0-5 volts) Accelerator Pedal Position (APP) Sensors The ETC strategy uses pedal position sensors as an input to determine the driver demand. 1. There are 3 pedal position signals required for system monitoring. APP1 has a negative slope (increasing angle, decreasing voltage) and APP2 and APP3 both have a positive slope (increasing angle, increasing voltage). During normal operation APP1 is used as the indication of pedal position by the strategy. 2. There are 2 VREF circuits, 2 signal return circuits, and 3 signal circuits (a total of 7 circuits and pins) between the PCM and the APP sensor assembly.  2 reference voltage circuits (5 volts)  2 signal return (ground) circuits  APP1 voltage with negative voltage slope (5-0 volts)  APP2 voltage with positive voltage slope (0-5 volts)  APP3 voltage with positive voltage slope (0-5 volts) 3. The pedal position signal is converted to pedal travel degrees (rotary angle) by the PCM. The software then converts these degrees to counts, which is the input to the torque based strategy. 4. The 3 pedal position signals make sure the PCM receives a correct input even if 1 signal has a concern. The PCM determines if a signal is incorrect by calculating where it should be, inferred from the other signals. A value is substituted for an incorrect signal if 2 of the 3 signals are incorrect. Electronic Throttle Body (ETB) and Accelerator Pedal Assembly Electronic Throttle Control (ETC) System Strategy The torque based ETC strategy was developed to improve fuel economy and to accommodate variable camshaft timing (VCT). This is possible by not coupling the throttle angle to the driver pedal position. Uncoupling the throttle angle (produce engine torque) from the pedal position (driver demand) allows the powertrain control strategy to optimize fuel control and transmission shift schedules while delivering the requested wheel torque. The ETC monitor system is distributed across 2 processors within the PCM: the main powertrain control processor unit (CPU) and a monitoring processor called an enhanced-quizzer (E-Quizzer) processor. The primary monitoring function is carried out by the independent plausibility check (IPC) software, which resides on the main processor.

http://iihs.net/fsm/?dir=7&viewfile=Torque%20Based%20Electronic%20Throttle%20Control%20(ETC).pdf

Customer: replied 2 months ago.
Ok David. I sure appreciate your patience. I've thrown in the towel on this one. I've went back to the vehicle and removed the throttle body completely, and removed the EGR valve and tube that extends inside the intake manifold. Super cleaned everything and reassembled. Now I start the vehicle and the rpm's fluctuate and then the vehicle shuts off every time. The OBD II live data showed that the Relative TPS percentage was moving to what seemed to be accordingly. The only way I can get the vehicle to stay running at idle now is to remove the vacuum lines from the EGR valve and then start the car and even then it stills surges. I'm going to start with what I know is definitely bad which is the catalytic converters. I've experience a similar situation about a year and a half ago with an 05 mustang, and the final fix was replacing the catalytic converters. Thanks a million for all the good knowledge.
Customer: replied 2 months ago.
Also, two last questions. What are normal tolerances for my Short and long term fuel trims? How do I ensure that you get paid for the outstanding answers that I received?

normal tolerances for stft are between negative 1 to +5

normal tolerances for ltft @idle are close to 0

normal tolerances for ltft at 2500 rpm are 2-10

https://www.obd-codes.com/faq/fuel-trims.php

please accept the answer and leave a 5 star rating for me if you were satisfied with my assistance. thanks and good luck.

replace the throttlebody assembly. i believe your idle will return to normal.

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thank you!