Erratic RPM needle

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Apr 25, 2006 | 11:30 AM

Hartwa

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Erratic RPM needle

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.

Apr 25, 2006 | 12:53 PM

pronstar

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

Apr 25, 2006 | 03:04 PM

Hartwa

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thanks Pronstar

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?

Apr 25, 2006 | 03:35 PM

machnegative

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From: Alamosa, Colorado

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.

Apr 25, 2006 | 03:36 PM

mach10533

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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.