Getting these codes
p0327 knock sensor 1 circuit low input
p0505 IAC system
p0135 02 heater circuit bank 1 sensor 1
P0155 02 heater slcircuit bank 2 sensor 1
And intermiintermittently it shows misfires on 2,4,6, and 8
just replaced wires with 8mm silicone
Replaced plugs first with platinum 4s then cheap copper ones
replaced knock sensors
replaced 02 sensors.
Nothing has changed, not sure if it's a wiring issue. Knock sensore wiring and 02 looks good.
I'm not very savvy with electrical systems so I'm not sure if the 02s and knock sensor have the same ground location that might be corroded or damaged.
engine runs fine. Especially for having 305k miles.
another issue is at cold start the engine revs up to about 1750 down to 1250 multiple times unless I wait a little or immediately put it in reverse and back to park real quick.
Trying to diagnose the problem and reading through the forums but I'm just stumped

 

We need a little more background info. How long have you had it? How long has it been doing this? The IAC valve is probably the cause of your high idle issue. Some people have had success cleaning it with carb/maf cleaner. You can test it by just unplugging it, engine will likely idle fine. The heater circuits are relatively simple, just 12v to the sensors. You can ohm them out and if the are open then the sensors ae bad, if not you have a wiring issue. Swap the knock sensors left to right and if the code does not follow you have a wiring issue, the knock sensor is a special shielded cable so you have to be careful repairing it.