i have a 1989 ford f150 pickup and today my rpm is jumping and while driving its starting to jerk. what could it be


Asked by May 01, 2014 at 05:11 PM about the 1989 Ford F-150

Question type: Maintenance & Repair

7 Answers


I'm curious as well I have a 92 that wants to jerk as your driving. Thanks

Tracy Hooks

A couple of quick checks: Warm the engine and spray the plug wires with a soapy mix of dish soap and water with a spray bottle. You should hear a snapping sound or maybe even see the spark jump. If everything is ok there, It's likely that either the Ignition Coil or Ignition Module is failing. The Tachometer is driven directly off of the coil and those E-core coils will fail internally while testing ok on the bench.


Throttle position sensor. Had same/similar problem with mine (mine's manual and only did it in neutral, so not sure how it would present in an automatic) Had all sorts of diagnostics and theories but turned out to be the throttle position sensor which is actually a really easy fix, so try that first.

Tracy Hooks

While that's a nice guess, I wouldn't go throwing parts at a problem without a diagnosis first. Just a waste of money.


Are you referring to me? If his problem is the same as mine was, and I believe it is, then it's DEFINITELY the TPS.

Tracy Hooks

Good luck with that. As a Master Certified Automotive Technician (Ford Motor Company and ASE), I can tell you that a TPS can have similar symptoms to many other failures. The only true way to diagnose a TPS failure is to check the signal back to the PCM. To have such confidence in something that worked for you once is fool-hardy. If I tried to repair vehicles with "I know what that is because I saw it once before" I certainly wouldn't be in the position I am in today - one of 12 Master Certified Technicians repairing and Maintaining a fleet of over 800 Police vehicles. Indeed. Guess work doesn't work.

2 out of 2 people think this is helpful.

I have a problem with the truck runs great till the engine warms up then after warm up the truck wants to jerk/Buck while driving and sometimes dies. if I put the truck in neutral or park revs fine idles fine. Any help thanks

1 out of 1 people think this is helpful.

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