Tron460

Hello all, recently I've noticed when driving and the RPMS go over 4000rpms the check engine light will flash on and off and throws a code for cylinder 5 misfire. I have tried swapping coils around and changing the spark plug. plug looked okay when removed. installed new one anyways. car runs better but still check engine light will briefly come on and go off when above 4k RPMS. Any ideas or thoughts?

Striker223

Not to make any assumptions but a few have had this issue and it turned out to be a headgasket for whatever reason. It always seems to be #5 as well.....

Do a leak down test to try and rule some stuff out

miket000

Sorry Tron460, not intending to hijack your thread. I started typing and got carried away.
Did the misfire stay on cylinder 5 after swapping coils? If you are using techstream, before you shut down you can check the current drive cycle. It may indicate other cylinders that are having minor misfires. My car doesn't save them on the main data screen.
For now I'd suggest injector cleaner, easy cheap fix if it works. Since my misfires started I've been feeding my car injector cleaner like it's candy. I recently picked up a few of these cans. I haven't tried them yet but the reviews are better than others. It may just be an overpriced bottle of kerosene
Some pictures / info at the link below for digging a bit deeper into misfires.
https://www.clublexus.com/forums/ls-...l#post11339636

Striker do you have any links to other cylinder 5 misfires? Aside from mine lol.

I started pulling my 600 apart to replace the valve stem seals. I figured it couldn't hurt seeing as every piston has an oil puddle on top. I'm doubtful it'll fix my misfire issue, fingers crossed.

I tested coolant for exhaust gas, none detected. Although since mine only misfires for a few seconds at a time I don't know if the coolant would have any exhaust gasses in it? I kinda doubt it.

Another possible misfire cause might be blow by on one of the lower injectors. Anfanger had misfires on cold starts caused by injector blow by, Neither Tron nor I seem to have issues on cold starts so I'm not sure how likely it'll be an injector.

There sure are more odd issues popping up as our cars age. Last week our 07 460 195k miles had codes for both banks being rich. I discovered the maf sensors have to be removed in order to fully spray them out. I had been spraying them out in the car. When removed there is another section of the sensor that isn't accessible with it installed. Cleaning the maf sensors cured my 460. If only I could be so lucky with the 600.


I'm curious to see what condition the old seals are in.

Striker223

There are some threads here from way back I read though before buying my 460, also found some similar issues with the 5.7 version and some hints of it in the repair network. To be very clear I'm jumping directly to the worst case scenario that is VERY uncommon in the first place but I am assuming all checks for fuel and spark and chain sync have been done already lol!