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Discussion Starter · #1 ·
Thanks in advance to those who read and assist...

I have recently acquired a 2006 Taurus SEL 3.0 OHV (non-flex fuel). It has just over 90k on it and comes from a family member who bought it from a dealer on a repo.

The car has no past major non-routine maintenance problems.

The symptoms are sluggish, rhythmic (as opposed to intermittent) "missing." feels like its running on four or five cylinders. Acceleration is at a crawl, and you better have a running start if you want to drive it up a hill.

They took it to a mechanic they trusted, who relieved them of $460 after telling them they needed to replace the computer. They were told that the dash needed to come out to get it out (Is that true for this car? Didn't look like it). They did not offer them any OBDII codes they came across. They parked the car for 6 months.

When I got here, I went simple, and replaced the plugs and wires and the fuel filter. there was no noticeable improvement. I replaced the coil pack to the same result. I was finally able to pull codes (Thanks Auto Zone) and got P0113 (IAT Sensor Circuit High) and P0352 (Ignition Coil B Primary/Secondary Circuit). the car does not run hot but appears to have poor fuel economy.

I am a shadetree mechanic of the worst degree, meaning I can probably replace it if it is broken by following directions, but have no knowledge of troubleshooting procedures, particularly with electrical test equipment. Even if I did know how, I have no access to it.

I have a alldataDIY.com membership for the car, but am having trouble navigating it to learn how to use it to get my moneys worth.

Please help! I have limited resources and am being given an otherwise fantastic car by a sister who doesn't need it anymore. All I have to do it get it rolling.

Thanks again to any who can lend assistance!
 

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The IAT is a thermistor device in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and increases as the temperature decreases, (proportionally in each case). This varying resistance affects the voltage drop across the sensor terminals, which allows for a voltage signal to be sent back to the PCM corresponding to temperature.

The voltage signal that is sent back to the PCM is equal to the Reference Voltage (VRef, 5 volts) minus the aforementioned voltage drop across the fixed resistor. That is why an open in the circuit between the PCM and the IAT will result in "too high" voltage signal at the PCM (i.e., 5 volts). In addition, corrosion in the circuit would tend to add resistance and hence result in higher-than-normal voltage at the PCM because of the signal being based on voltage drop.

In any case, if the circuit checks out OK, then it's either the IAT sensor at fault, or the PCM.

If you don't have a DVOM to check the resistance than I would just replace the sensor, think it's 30 bucks. Would be a good start to see if it fixes the problem. After replacing get the codes cleared and see if the P0113 stays off. Then see if the P0352 is still there, if I had to guess I would say a bad wire at the connector at the coil pack wiring harness. Might have gone bad when you replaced the coil pack.
 

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Discussion Starter · #3 ·
The IAT is a thermistor device in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and increases as the temperature decreases, (proportionally in each case). This varying resistance affects the voltage drop across the sensor terminals, which allows for a voltage signal to be sent back to the PCM corresponding to temperature.

The voltage signal that is sent back to the PCM is equal to the Reference Voltage (VRef, 5 volts) minus the aforementioned voltage drop across the fixed resistor. That is why an open in the circuit between the PCM and the IAT will result in "too high" voltage signal at the PCM (i.e., 5 volts). In addition, corrosion in the circuit would tend to add resistance and hence result in higher-than-normal voltage at the PCM because of the signal being based on voltage drop.

In any case, if the circuit checks out OK, then it's either the IAT sensor at fault, or the PCM.

If you don't have a DVOM to check the resistance than I would just replace the sensor, think it's 30 bucks. Would be a good start to see if it fixes the problem. After replacing get the codes cleared and see if the P0113 stays off. Then see if the P0352 is still there, if I had to guess I would say a bad wire at the connector at the coil pack wiring harness. Might have gone bad when you replaced the coil pack.
Thanks!

I know that the engine ran the same way before I replaced the coil pack, so whatever was wrong happened before. I will take your advice and see how that goes and let you know.

If it is a bad wire, is it as much of a nightmare as I think it will be? And if so, will I have to rely on someone to test them? Is that possible?

Also, is there a way to clear the codes without going to someojne who will charge me for using the OBDII checker?
 

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If you have an andriod phone grab a bluetooth obd2 adapter for around $50 on ebay, then buy the torque app on your phone. I have only had it for maybe a month and have been payed 3 six packs, a pizza and a free car wash for checking codes on friends and co workers cars plus its just great to have for your own car.

Other than that trusty autozone boys will check yout cel for free. And resetting the battery will delete them if you know whats wrong.
 

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Discussion Starter · #5 ·
If you have an andriod phone grab a bluetooth obd2 adapter for around $50 on ebay, then buy the torque app on your phone. I have only had it for maybe a month and have been payed 3 six packs, a pizza and a free car wash for checking codes on friends and co workers cars plus its just great to have for your own car.

Other than that trusty autozone boys will check yout cel for free. And resetting the battery will delete them if you know whats wrong.
Wow. You learn something new every day. That's pretty cool.

As far as a battery disconnect, does that clear codes as effectively as someone hooking up a reader and clearing them that way?
 

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Yes it does, and when i got my inspection sticker the old guys at the shop freeked when they saw the obd adapter, but of course they are old school using some alldata type progam on cd and they domt even have an internet connection!
 

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Disconnecting the batt to clear the codes and clearing them with a scan tool are NOT the same!!! Both methods clear the codes and reset the IM monitors, but when the batt is disconnected, the PCM looses all of its adaptive information stored in the KAM (Keep Alive Memory), such as tranny adaptive shifting parameters, fuel trims, IAC adaptive parameters, etc. A good scan tool will allow you to reset the KAM without erasing the codes. Clearing codes with a scan tool does not loose all the adaptives.

The dash does NOT need to be removed to get to the PCM!!!! It comes out from under the hood. It is located at the top of the firewall on the pass side.
 

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Discussion Starter · #8 ·
Well, shoot...

I have replaced the coil pack, spark plugs, wires, fuel filter and now the IAT sensor. No go. Replacing the IAT cleared the code for that, but I am still getting a P0352 code.

I have tried shaking wires all the way back to the PCM, but to no avail.

s2knott>>> Thanks for that tip! I picked up the Bluetooth OBDII adapter for $30, grabbed the Torque (full) app for $5.00, and am awaiting a Bluetooth dongle for my laptop. The Torque app is great and worked wonderfully. Cleared codes and did all it was supposed to do.

Now if I could get it to actually FIX the problem... lol

Any more suggestions, anyone?
 

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If the coil is good then I would check the wire harness to the coil. Could have bad connection or something in there. I'm also doing a car that the #1 cylinder is not getting spark, replaced the plugs and wires and still no spark. Going to change the coil next and hope that fixes it.

I would take the wire harness off and check things out, look for loose wires, bad terminals, corrosion, or anything else not right.
 

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Here is what Mitchell on demand has to say about this PID - See attachments.
 

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Discussion Starter · #11 ·
Thanks!!

Here is what Mitchell on demand has to say about this PID - See attachments.
Awesome.

I have been out of pocket for a couple weeks, and just now was able to check this. This is great. Some of it is above my current sphere of ability, but I am sure I can learn it provided I collect the right tools. I have most of it.

So far, since all of the other stuff, I have tested the conductivity of all four wires from the coil pack to the PCM, and checked them for shorts to ground or themselves. Nothing. I saw no corrosion or moisture, and blew out the PCM harness while I had it apart. I also tested the start/run pin and it showed 12.5 to 13.5 volts (analog sweeper I am having trouble reading).

I keep feeling like I am going to have to pull the PCM and get it flashed. I am hoping not, but if I need to, does anyone have any suggestions about who to send it to that is reasonable?

Any other suggestions apart from the:D troubleshooting stuff that 00greenlx sent?
 

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When you replaced the coil pack, did you replace it with a Motorcraft part or aftermarket ?

There have been others on this site that have had trouble with aftermarket coils.

Also, what brand plugs were put in the vehicle ?
 

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^^+1

Coilpack is prime suspect at this time, even though you have gotten a 'new' one based on what you have reported as checked out.

If you are still getting P0352, the coil driver that sends spark to cylinders 3 and 4 may be bad.

Check the resistance between pins 3 (connects to yellow/red wire on cable connector) and 4 (connects to solid red on cable connector) on the coil pack connector. Facing the engine, it would be the 2 right-most pins on the coil pack. Should be 5 ohms or less. If it shows open, coil pack needs to be replaced.
 
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