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Author
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Topic: Stock tachometer bouncing up and down?!?!
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SydeWaySix
CAFords OG
Member # 3596
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posted
 
 
I noticed this morning that my stock tach is acting up. Sometimes it'll get stuck, then all of a sudden jump up to the correct RPM, then fall back down, etc...
It seems to be fine when cruising down the freeway, but off the line and at lower speeds it jumps around.
The only thind I did this weekend was change my spark plug wires and hose down the engine...could I have messed up a wire or something?
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2013 Boss 302 #356. Performance White. Stock.
1965 Fastback GT Restored to stock spec.
Posts: 9882 | From: Bay Area | Registered: Dec 2002
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BCINGUU
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Member # 2397
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posted
Could be a few things. The internals of the tach may be gummed up causing the needle to actually stick (you could try swapping tachs). Could be a loose wire, or perhaps the fuse connection is flaky (may be rusted, try jiggling or replacing the fuse).
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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SydeWaySix
CAFords OG
Member # 3596
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posted
quote:
Originally posted by BCINGUU:
Could be a few things. The internals of the tach may be gummed up causing the needle to actually stick (you could try swapping tachs). Could be a loose wire, or perhaps the fuse connection is flaky (may be rusted, try jiggling or replacing the fuse).
which wire could be loose? Is it under the hood?
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2013 Boss 302 #356. Performance White. Stock.
1965 Fastback GT Restored to stock spec.
Posts: 9882 | From: Bay Area | Registered: Dec 2002
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BCINGUU
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Member # 2397
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posted
I believe the tach signal comes directly from the PCM, so it would just be a wire under the dash. Have to look at a wiring diagram to see which one it is. I think it's more likely to be a rusty fuse connection or gummed up tach though.
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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josesiphone
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Member # 8693
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posted
tach signal come from the ignition coil. Stock gauges aren't reliable so yours might be going out.
[ October 13, 2008, 04:28 AM: Message edited by: josesiphone ]
Posts: 40 | From: Lathrop | Registered: Oct 2008
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whitelx91
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Member # 8317
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posted
Definately wiring somewhere or tach sticking pretty common. Check the wiring coming off the pcm to the coils, PIN 48 on the ecu is the tach output check that going to the dash as well. Good luck.
SuistangS
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SuistangS
Posts: 380 | From: Sacramento Ca. | Registered: Apr 2008
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408LIGHTNING
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Member # 7447
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posted
quote:
Originally posted by BCINGUU:
Could be a few things. The internals of the tach may be gummed up causing the needle to actually stick (you could try swapping tachs). Could be a loose wire, or perhaps the fuse connection is flaky (may be rusted, try jiggling or replacing the fuse).
WOULD IT BE THE SAME IF IT STOPPED WORKING AFTER 4OOORPM? CUZ MINE DOES THAT ![[Confused]](confused.gif)
[ October 15, 2008, 04:38 PM: Message edited by: foxstang ]
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**R.I.P Willie Guzman 5LTRSVT**
1988 lx hatch
2000 ford lightning
2007 sonic blue ZR1
Posts: 527 | From: san jose | Registered: Feb 2007
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