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Superbob, Senior Master auto technician
Category: Car
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Experience:  Ford Lincoln, Mercury, Seinor Master, diesel certified, mazda certified, ASE Master
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2005 Ford Taurus SE: 3.0L..V-6, OHV...transmission failure light came

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The car is a 2005 Ford Taurus SE,3.0L, V-6, OHV. The transmission failure light came on the other day. Oil is clean and does not smell bad. Gear changes are normal up to about 2000 rpm on a normal morning start-up; then just a little more gas and the transmission will down-shift to 3rd gear and engine RPMS go up (naturally) to about 3000 RPM. This occurs on level roadway. The speedometer will be at around 60 MPH. I will take my foot offf the gas and then the transmission will shift back into 4th gear and I will ease a little more accelerator and it will be fine and maybe I willl get 65 MPH. I have considered pulling the Trans. pan and changing the strainer. Any other suggestions? Your prognosis,please.
The first place to start is to find out what code has been set in the PCM! When the light comes on, a code is stored in the computer! Once we have the code we can develop a diagnostic strategy and get you a pinpoint test to better isolate the cause! If you can get the car to your local auto parts store, ask them to run a free code scan! Most codes are able to be retrieved with the kind of scan tools that auto parts have, but not all! If the code will not come up with their scan tool, you will need to locate a place that has a more advanced scan tool! There are hundreds of codes that could be set, and this would be step 1 !
Customer: replied 4 years ago.
Another symptom.....If sitting too long at a red light, the car will start idling real rough and then die and the transmission failure light will come on. When this happens, we have to sit about 60 seconds before the car will restart (the trans. failure light will go off), then we can continue our trip. I have a code rreader I purchased on E-Bay. The only codes I am getting are PO 171 and PO 174 which are related to my fuel pump problem (it needs to be replaced). Maybe the two problems are related? I do not mind replacidng the fuel pump, est. $500.00 but I do not want to replace the transmission.
The lean codes that you have can and are more likely caused by a vacuum leak! Any air that enters the engine that is not measured by the mass air flow sensor will cause these codes! The mass air flow sensor is the main vehicle sensor responsible for fuel injection timing and load calculation! It also is the main sensor that determines the transmission shift schedule! I suspect the mass air flow sensor is dirty and cannot correctly read the incoming air to the engine! You can clean this and test the car to see if the symptoms improve! The mass air flow sensor which is located just to the engine side of the air filter in the intake air stream works as follows: It is a microprocessor that provides a specified amount of amperage to a coiled wire that is in the air flow stream, the coiled hot wire is maintained at a constant 300 degrees Fahrenheit, as intake air flows across the coiled hot wire it cools the wire, the microprocessor has to add amperage to the circuit to maintain 300 degrees on the wire and this amperage is measured to determine how much air is entering the engine! If the hot wire get dirt, oil, insects, or other debris in front of it, it will miscalculate the amount of air entering the engine and the fuel trims will change and indicate that less air is entering the engine than really is and then the oxygens sensors in the exhaust stream will indicate lean and set the codes that you have! I would advise that you take the air filter lid off and take a Q-tip and dip it in rubbing alcohol and lightly swirl the Q-tip on the hot wire to the MAF sensor! Do not press hard as this wire is fragile!
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Customer: replied 4 years ago.
Please, accept my apologies for being so long in replying. The car is being used every day. I did have time to clean the MAF sensor, without any positive results. I have a digital multimeter with a piercing probe and am now ready to test the sensor. It is a six lead sensor. Can you give me the proper testing procedures?
The MAF sensor is a microprocessor and there is no testing procedure that you can do with a multimeter! At the dealer, when we have an issue with a MAF that is not corrected my cleaning, we generally replace it once we are 100% certain that there are no vacuum leaks! The fact that your transmission failure light is coming on indicates the problem is a MAF sensor, or you have two separate faults in the vehicle, #1 causing the lean codes, #2 a transmission problem causing the trans light! Please note that not all codes stored in the PCM can be retrieved by (NON-FORD) scan tools! Only codes that are OBD II compliant are the codes that can be retrieved by scan tools like the ones found at auto parts stores! After reviewing your second post about the idle issue, it definitely sounds like a vacuum leak! I would advise that we address this issue before the transmission issue and see if that isn't also corrected with the same repair! Acquire a can of aerosol brake parts cleaner, and with the engine cold, start it up and spray the cleaner in an isolated fashion around different areas of the top of the engine while listening for the engine rpm to change and listen for a hissing sound from a disconnected or damaged vacuum hose to see if you can isolate a vacuum leak! When we do this at the dealer, we have a scan tool connected and we look at the oxygen sensor reading while spraying the cleaner to look for a rich signal! If the leak is very small, you may not detect the change in engine rpm!
Customer: replied 4 years ago.
One other symptom. I unplugged the MAF sensor with the engine hot and idling. The reaction was immediate. The engine started shaking and then died. I plugged the sensor in and restarted the engine. The engine RPM was around 750 and the engine idled smooth. I have tried pushing, pulling and moving the vacuum lines around, without creating a noticeable vacuum leak. I will try try the aerosol brake cleaner method, as soon as I can. I will let you know the results. I appreciate your patience, Bob.
The result you had by unplugging the MAF is a normal response of a good MAF, If the engine was running poorly prior to unplugging the MAF and straightened up after unplugging it, would definitely indicate a bad MAF

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