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I've been trying to narrow down the cause of a P0305 code that my car throws only under very specific cruise conditions (freeze frame attached) .
O2 sensors are new Denso, plug wires and plugs are recent, tried switching the injectors around too but the code persists so I had a look at the valve train. Pushrods are straight, rockers are good. However, when I push down on the valves, the behavior of the intake valve on #5 is odd. It sticks a little in the very beginning and the spring makes an audible creaking sound as it opens. It doesn't make a nice metallic sound as it closes like the other valves do. You can hear this with earphones in the attached video.
The motor also makes a rattling sound like a bad lifter at high RPM under hard acceleration. It sounds like almost like detonation from bad gas but I'm guessing it has something to do with this intake valve. There are no odd noises at all from this motor otherwise. No ticking, rattling etc at all during normal use, none of the other telltale signs of a bad lifter. Oil pressure is good too.
Now the question is, what's going on with this valve? Is it bent or just cruddy, and how to fix it? Thanks in advance!
The motor looks too clean for a sticky valve, although only you know its actual cleanliness. So, I would remove the retainer after filling the cylinder with air pressure and check for a broken or cracked spring first. Then check the valve for movement in the guide. It should glide up and down freely with no side to side movement. If it doesn't then its time to do a valve job.
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Sticky intake valve and P0305 
