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My 2005 Ford Expedition seems to Jerk pretty bad after ...

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My 2005 Ford Expedition seems to Jerk pretty bad after getting warmed up driving on the HWY. Trying to keep a constant speed of roughly 70 mph, the truck will hesitate badly and jerk to the point that you would think that I was jamming the accelerator pedalup and down. This is even with the Cruise Set.
The truck has 41k on it. The fuel filter and Throttle posistion senseor has been recently replaced as well.
Submitted: 10 years ago.
Category: Ford
Expert:  AMEDEE replied 10 years ago.

Greetings! Three things come to mind. All three are very important!

U could have a bad mass air flow sensor. This is very common and can cause you vehicle to loose power along with many other drivabilty issues if the sensor is bad. The Mass Air Flow (MAF) sensor uses a hot wire sensing element to measure the amount of air entering the engine.
The MAF sensor then outputs an analog voltage signal to the PCM proportional to the intake air mass. The PCM calculates the required fuel injector pulse width in order to provide the desired air/fuel ratio.
If the sensor is bad than this air/fuel ratio will be off.
This input can also be used in determining transmission Electronic Pressure Control (EPC) , shift and torque converter clutch scheduling.
Some MAF sensors have Integrated Bypass Technology (IBT) with an integrated Intake Air Temperature (IAT) sensor.
The MAF sensor is located between the air cleaner and the throttle body or inside the air cleaner assembly.

U also could have a lazy or bad oxygen sensor. The heated oxygen sensor is very important to control not only the cars emissions but it also helps the vehicles performance! If it is not working properly it can result in a number of problems like rough running stalling hesitating bucking and jerking. But more common than that if it is lazy, the cars gas miledge can drop considerably, and sometimes not even set a check engine light on the dash!
The fuel control Heated Oxygen Sensor (HO2S 1) is mounted in the exhaust manifold where it can monitor the oxygen content of the exhaust gas stream. The oxygen present in the exhaust gas reacts with the sensor to produce a voltage output. This voltage should constantly fluctuate from approximately 100 mV (high oxygen content - lean mixture) to 900 mV (low oxygen content - rich mixture). The heated oxygen sensor voltage can be monitored with a scan tool. By monitoring the voltage output of the oxygen sensor, the PCM calculates what fuel mixture command to give to the injectors.

And last but not least, sounds like u could have bad tune up parts. They usually go bad under a load like under acceleration. But also can go bad at any time. It is very important to have your engine equipt with good tune up parts. If your vehicle is misfiring because of tune up parts than than can cause premature catalytic converter failure. Very common! Good luck!

Expert:  HDGENE replied 10 years ago.
Sounds like you have an engine misfire. These trucks have had an issue with the fuel injectors becoming either clogged or dumping straight open. It is most likely an engine misfire you are experiencing. A diagnostic check for codes will indicate any engine misfire or fuel injector concerns.Dealerships also have the ability to check MODE 6 data which will say if a cylinder is misfiring before it sets a check engine lamp.You are out of base warranty but if you have any type of Extended service plan from ford or another company they may cover your repairs.
Customer: replied 10 years ago.
Reply to HDGENE's Post: FYI, I stopped and checked at the local Parts store and had the computer checked. There was no setting for a 2005 Expedition so I had it set to the late3st which was an '03. It said that I had both Bank 1 & 2 running lean. The guy recommened an Injector cleaner and that was about it. I thought that it was a bit simple for as bad as the bucking was.
Expert:  HDGENE replied 10 years ago.
With both banks running lean it is either a problem with a fuel pump going bad/starving for fuel or a vacuum leak possibly from the pcv valve hose they tend to collapse and suck in extra air, the MAF sensor is a possibility but all items should be checked, fuel pressure when then concern occurs.
Customer: replied 10 years ago.
Reply to HDGENE's Post: With the OBD2 scan that was completed is there a change in the ECU between 2003 and 2005? The reason that I ask is that is what the scanner was set to when it was hooked up. 2005 was not available. Also at another store the scanner that was hooked up would not even turn on.
Expert:  HDGENE replied 10 years ago.
Yes, 2005 uses a CAN network.If the scan tool is not CAN compatible,it will not work.
HDGENE, Ford Senior Master/Diesel/Trans
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