the needle bounces about 500 rpms and drives me crazy, it just happened a few days ago. How do i stop it?

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late model 91 rs
fully loaded t-tops
red leather
paint- gm red and yellow blend (light red)
custom pink rims
305 tbi k&n,computer chip
MTX sub and amp (very loud)
vic_v8@yahoo.com

 

Is it an aftermarket tach or stock? It could be the connections (worked loose, or wired wrong). It could also be interference from the ignition system. How old are your spark plug wires? Ones that are old or have poor insulation can cause electrical gauges to bounce around and give false readings.

If I'm not mistaken solid core wires can cause this problem. You may want to try spiral core wires. I may be wrong about this. Does anybody agree/disagree?

 

I just noticed that you have a stereo amp and sub. Do any of their wiring come near the tach or ignition system. Those stereo amps put out a great deal of current. The interference could be coming from this.

 

my amp was professionally installed when my cousin had the car. It had a full tune up about a year ago. I've had the car since August and no problems with stock tach. I'll check for loose wires on friday, but keep replying jusr-incase it isn't the connenctions.

 

My car did the same thing when my plug wires were fried by the headers. I agree with Coach, replace the wires and that should correct it.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End with 2.77:1 Gears.

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

Soon to Come: 7.625" 10 Bolt with 3.42s and Accel TPI Intake Base