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tach needle goes to redline on startup ?!

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Old 02-05-2007, 11:19 AM
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Car: 1987 IROC-Z
Engine: 406 on N20 w/ EFI
Transmission: P.B. 700R4
Axle/Gears: 12 bolt w/ 3.91
tach needle goes to redline on startup ?!

im in the process (and almost finished) cleaning up my engine bay, moving wires and stuff around, painting in there, relocating things.. and i hooked up the battery to runt he car last week, and it ran good; jsut a little smokey cuz i didnt have the MAF sensor plugged in. when i revved the car the needle ont eh tach was NORMAL

today, im inthe garage again, and needed the battery hooked up to put up the windows in the car; and i hook up the battery; and MAF sensor too; and as soon as i turn the key to IGN, the tach needle maxxes out (goes to 7000 redline), i turn the car on, and the needle STAYS there, but the car idles normal (about 1200) and revves up just fine, but the needle is pinned at 7000 - maxxed out

any ideas?
fuse?
wire?
other problem ?

thanks
dave

Last edited by IROCZman15; 02-05-2007 at 01:06 PM.
Old 02-05-2007, 12:39 PM
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Car: 87 Camaro IROC
Engine: 305 TPI
Transmission: 700r4
Axle/Gears: 3.23
sounds like bad wires, check the wires at your distributor and coil, mayb you jarred something or thers a wire with a bad connection.
Old 02-05-2007, 04:02 PM
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Car: 1987 IROC-Z
Engine: 406 on N20 w/ EFI
Transmission: P.B. 700R4
Axle/Gears: 12 bolt w/ 3.91
thanks gramps; you were right

i must have bumped one of those wires and made the connection loose, so i went int here and loosened up the tangle of wires a bit,a nd now the needle is reading normally again, thanks dude
Old 02-05-2007, 04:25 PM
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the tach signal is a white wire. if your tach is reading max then its shorting against something. i'd do more than move the spaghetti around. you might wanna find the wire and isolate it.



smith
Old 02-05-2007, 08:36 PM
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Car: 1987 IROC-Z
Engine: 406 on N20 w/ EFI
Transmission: P.B. 700R4
Axle/Gears: 12 bolt w/ 3.91
i was going to do that; i was just reading my 1987 SHOP manual, and discovered that it is the white wire; i will trace it tomorrow afternoon when i get home from work

thanks for the replies fellas,

i also think that is has something to do with my alarm setup (that the original owner had installed)
-its a "chelsea alarm" which is a button that when you push it in, it cuts off signal to the distributer, and locks down the hood(well used to, on the steel hood, now mines glass), because i also was fiddeling with the alarm wires during the past few days

ill trace the wiite wire tomorrow and check it on a volt meter
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