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Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 48626
Experience:  16 years experience
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2002 f150 4x4 136K 5.4 experiencing shudder on light pedal

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2002 f150 4x4 136K 5.4 experiencing shudder on light pedal pressure slow to normal start ups from stop. Also feel same shudder or bucking in over drive between 40-45 light pedal pressure. Turned off overdrive with button on shifter and still does it but not as bad because rpms are higher which seems to help. It does not do it when the engine is cold and seems worse when its hot outside. Plugs are new. K&N air filter and dual exhaust after the muffler.
JA: Does the light flash or stay on steady? Do you happen to have the trouble code?
Customer: Its never stored a code or had light. Had shop drive it with some diagnostic tool hooked up and no misfire recorded during shudder and fuel pressures were normal.
JA: Are you fixing your F150 yourself? What have you tried so far?
Customer: Just plugs and ruling out torque converter. Guessing coil at this point because worse when hot.
JA: Anything else you want the mechanic to know before I connect you?
Customer: Nope. Truck seems to have lost some power overall but it also got alot hotter out with increased humidity

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This sure sounds like a coil going bad but the test they ran while driving should of picked up on this if it occurred while driving. Did they run a power balance test and a check of the mode 6 data?

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Customer: replied 1 month ago.
Hi Chris. It did occur during their drive but never registered a misfire. I'm not familiar with the power balance test. Will this identify which cylinder has weak coil

Yes a power balance will tell you when and which and how often a cylinder is misfiring.