recently bought older civic 180k,
recent shop tune-up w/timing, belts chged.

P0304, but one instance of P0300, 0301, 0302 each too.
trying DIY, cleaned IACV... apparently no EGR w/ DX.

started fine afterward, for 5-6 min till warmed up...
then idle surge... unplugged IACV and it seemed to idle fine...

is this simple evidence to replace IACV or should I
address 'fast idle valve' somehow before ordering replacement?

Any other things to check first? or as well?
( did compression testing... 1912, 170, 185, 180)

 

Does the car drive OK other than not idling smooth?

Check that the radiator is full (when cold). Coolant sloshing around in the engine can cause an unsteady idle.

 

There's is a noticeable lack of power when the misfiring occurs
after being warmed up... so I'm not driving it until I can fix this
and looking for relatively simple DIY checks...
The car obviously not worth much but was a great runner at 38-40mpg.
Any suggestions much appreciated.

 

A while ago, the coolant was low in reservoir and possibly in engine for a bit,
fixed with adding coolant and burping, maybe 3-5k miles before problem
occurred. Coolant is full in radiator when cold.

 

If it misfires while driving, especially heavy throttle and low rpm, that is usually weak sparks-- and the spark wires are a prime culprit. Some aftermarket wires are really bad and only last a few months.

 

fyi...
put in new iacv -> fixed surging idle, but not misfires...

installed OEM spark plug wires (NGK 8034 HE76),
(and new spark plugs denso(4504) PK270TT)

This fixed misfires/power loss, so car running fine! :-)

thanks for replies... appreciated

note: there was 30k miles on old plug wires
labelled "STI Spark Transfer International"