I have an 02 F150 Supercrew with a 5.4L.

Sometimes I notice when I am crusing about 55-65 that the tach needle flutters from 1500 to 2000 RPM's while at a constant speed. The needle is moving but the actual RPM's on the engine is at a constant idle...I am sure that the engine is at a constant idle since you can tell / hear when it shifts down.

I am sure that this is a problem with the tach itself but I am not sure where to begin to fix it...I have not pulled it out yet but I am sure that it is all electronic.

Any ideas would be appreciated.

Hartwa.

 

Often, things like this are due to a faulty ground, so your gauge may be OK.

 

Any idea where the instrument panel gets ground? I did just remove my battery cables to work on something else. Could the negative cable have a bad connection?

 

I have an erratic tach on my 1997 f-150 and haven't found the cause either. I have been looking around for info on the cause, but haven't found it yet.

 

the little small ground wires that hook to the main ground cable that go over to the body often get broken inside the insulation or corroded and could cause problems.