The tachometer fluctuates and there are a few codes coming up

1999 HONDA CIVIC
204,000 MILES • 1.6L • 4 CYL • FWD • MANUAL
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ANDREW SISLER
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  • 1 POST
the tachometer when you start the car sometimes does not move and then sometimes it does. there are codes coming up on my OBO scanner keep coming up, PO505, PO313 and PO330. can you tell me how to fix it?
Dec 22, 2016 at 1:06 PM
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STEVE W.
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PO505 - IAC (Idle Air Control) System Malfunction
PO313 - Misfire - Low Fuel Level
PO330 - Knock Sensor 2 Circuit Malfunction

I would check for wiring harness damage, The first and third codes are saying that the computer cannot control the IAC and does not see the knock sensor. Wiring damage could cause both as well as the intermittent tachometer signal.
The misfire could be caused by a bad control wire to the injector.
If you do not see wiring damage then check for a vacuum leak.
Dec 22, 2016 at 8:02 PM