2001 Lexus RX300 with CEL and VSC light. OBDII Code P0302. 257k mi. Replaced plugs, coil pack and VVT solenoids and #2 fuel injector...no help. Runs great at road speeds but rough idle (with CEL and VSC). Also removed and cleaned IACV. Noid test good. Compression on cylinder #2 low 60 psi (dry). 150-160 psi on #4. My question is ...Can a bad Idle Air valve cause all this? Ran great right after cleaning the valve, but after 3 miles the lights came back on. Thanks

 

IACV will not cause low pressure in the cylinder. It just bypasses the throttle plate when it is closed to allow air into the engine.

 

Thanks...Grasping at straws

 

You could try something called Engine Restorer, which is supposed to increase cylinder compression. Not sure what you have to lose at this point with such low compression in a cylinder. Maybe someone else can weigh in on using it.

Lexmex, a longtime poster here, said he used it in his RX300 in this thread:
https://www.clublexus.com/forums/gs-...-restorer.html

the material
https://www.restoreusa.com/index.php

A real world example

 

Sounds like a burnt exhaust valve. Try some sea foam thru the pcv hose to clean the valve seats. Top end cleaning. It may not be too late to have the valves re shimmed.