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Discussion Starter #1
what would cause the rpm tac to jump up and down non stop on a 94 civic. another question when i have the ac on it takes it a while to take of from a full stop, but when ac is off it takes of regular from a full stop
 

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a/c takes power away from your engine when its running thats why, and there are many reasons why it would jump, timing is off/IACV is messed up/vacume leak
 

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ES1 Civic
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a/c takes power away from your engine when its running thats why, and there are many reasons why it would jump, timing is off/IACV is messed up/vacume leak
check your sensors & plugs
 

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even if the ac is on,it shouldnt have any trouble taking off from a dead start. My car runs fine with the ac on with the no problems taking off at all. Whats your power plant,you may just have a weak p.o.s. engine. And like sr20s13 said,many things can make your tac jump. I know on my old accord the tach jumped whenever i went past 3000rpm. So i started by changing the spark plugs and that fixed it
 

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wait, is your engine jumping or just your tack?

and i'm guessing he has most likely a D15B7 103hp always has trouble from a stop and its prob. a old engine and tired
 

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I have a bouncing OEM tach and I'm pretty sure it's the dizzy coil again. Checked and swapped a VSS and that wasn't it.
 

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Discussion Starter #8
well my head gasket was bad it was leaking oil i changed it set the timing and its taking off normal now with the a/c on and all:mikej:.... but my tack keeps on jumping at 3000rpms do you all think its a bad IACV or a vacume leak but no engine light is on...the block is d15b7 with a d16z6 head.... i also have a new dizzy, wires, spark plugs, the vss had gone out so changed that too.... thanks for all your help guys
 

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bad IACV or a vacume leak
 
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