cleaning iac valve / misfire

hi again will cleaning the iac valve help stop misfire I have replaced plug and wires did compression check and only intermittent get p0301 code. I'm cleaning iac valve and throttle body any other ideas of what might cause random misfire?

 

What engine do you have? You could try swapping ignition coils around and see if the misfire moves with it. Along with proper compression (which it sounds like you checked), you need air, fuel, and spark. Air issues usually don't just affect one cylinder, but I guess it could happen. So, fuel and spark would be next. Ignition coils, wires, plugs for spark. Fuel pump and injectors for fuel.

 

99 tacoma 2.4l 441000 miles compression was.good I replaced the coil.pack on 1,4 but still random misfire

 

Does it misfire just at idle, like a stumble, or at all RPM's? If just at idle, you may be on to something with the IAC, but I would still expect the misfire to move around a bit. The other major contributors to the spark side are the camshaft position sensor and the crankshaft position sensor. Cheap replacements can be found on RockAuto, but if that fixes it, I'd eventually replace with Denso.

I don't have any specific knowledge on that engine, so I'm just spitballing here on what I would look at. After ignition, I'd look at injectors.

 

just a idle and usually only.when it's cold.i already replaced all the injectors so I'm hopingit is the iac valve

 

Yeah, that's where I would go if just at idle. Also check vacuum lines for old and cracked hoses, PCV valve, stuff like that. My old '77 Celica with the 20R had like 20 feet of vacuum lines and way too many vacuum switches.