Hi all. I have a 2008 ls460 that's at 160k miles. Right now I have an intermittent misfire. I've looked around and haven't found anyone with the same problems I'm facing.

So symptoms are the misfire p0300 and it occurs on all cylinders but it's odd as it will Rev fine until the misfire happens then it will almost hit a Rev limiter. It sounds similar to a 2 step system. This started happening at around 5 k rpm but then it started happening at lower and lower rpms. Another symptom is a squealing noise coming from the engine bay after I let off from the misfire. As of yet it doesn't misfire at all when idling or under 1.5k rpms

I've already tried taking off the accessory belt and running the motor. The misfire still occurred in the same exact way. I have suspicions of the transmission but I haven't been able to check the fluid or top it up.
any advice would be extremely helpful.
Thanks for your time.

 

Is the MIL blinking or steady?

 

I'm assuming CEL? And it blinks when the misfire happens but once i let off and let it idle it goes away after about 30 seconds. Using my code reader i can see that it's stored in the pending codes as a p0300 but the active code goes away.

 

Blinking P0300 indicates that high temperature misfire happens in three-way catalytic converter. Proper troubleshooting requires Techstream. However, P0300 is caused by one of the following:
- bad spark plugs
- bad fuel
- bad fuel delivery system
- vacuum leak

 

maybe related then but recently ive had a bank 2 cat code and ive been hearing rattling from that side exhuast. Could it just be a majorly clogged cat? Would replacing it be a fix. Also doing some further testing I had misfire codes for cylinders 8 and 2 pop up alongside the random misfire.

 

Also I replaced the spark plugs about 5k miles ago

 

Fuel pressure...

 

what part points twords fuel pressure. Would the squeaking be symptom of that?