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Mat
Mat, ASE Certified Technician
Category: Transmissions
Satisfied Customers: 947
Experience:  Ase master auto technicianwith L1 and L2 Ford Lincoln Mercury senior master tech specializing in auto trans
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Ford F150 Pickup Super Cab: I have a 2007 F150 King Ranch edition

Resolved Question:

I have a 2007 F150 King Ranch edition with the 5.4l V8. I have a "shifting"problem. When I accelerate through the gears all is fine. When I am cruising along maintaining speed and start up a gradual incline, I'll add slight pressure to the gas pedal. The transmission thumps down into a lower gear and then goes back into the original gear. It is like the tranny doesn't know what gear to stay in. It may happen once or it mat go thump thump thump. Once I reach the desired speed on the incline, all is good. I think it is a vacuum problem but I have no way of telling.
Submitted: 11 months ago.
Category: Transmissions
Expert:  Mat replied 11 months ago.
Hi I would like to help you out. Usually when you cruising at a steady speed the transmission will be in higher gear and torque converter may be locked up to reduce engine rpms and save fuel. This is when the ignition coils work the hardest and are under the most stress. Commonly a weak ignition coil will fail at this time. It creates a quick thump felt in the vehicle, may go multiple times or may do it just once. This is actually a very very common problem that 99% of all customers think is a transmission problem. But the symptoms are that of a weak ignition coil. Simply stated your at the early stages of a coil failure or constant misfire. There are 8 separate ignition coils on this engine, one for each cylinder. The check engine light will eventually come on but the misfire rate has to be greater than 22% to set off the check engine light. Your misfire is not that bad yet, most likely not even t 1% yet. To diagnose this concern you have a couple options, first the dealership and maybe some outside shops will have a Ford IDS scan tool that can do a powerbalance while driving, once the concern is duplicated the technician can simply look at the laptop graph to see which cylinder caused the misfire. Second is if you have a scan tool (higher end one) you can access MODE 6 DATA in the pcm, this will display the misfire rate for each cylinder, the one that is not a 0% is the cylinder at fault. We do a ton of ignition coils for the same exact symptom you described. Also note a vacuum concern is no likely since the transmission is only electronically controlled, no vacuum. A vacuum leak would cause a very poor running engine and check engine light. If a transmission slipping or gear hunting concern was present the o/d light would flash rapidly on the dash when the concern is present. Based on your symptoms the truck appears to have a weak ignition coil. if you have any further questions or concerns please reply. Thanks
Mat, ASE Certified Technician
Category: Transmissions
Satisfied Customers: 947
Experience: Ase master auto technicianwith L1 and L2 Ford Lincoln Mercury senior master tech specializing in auto trans
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