Jerkey

Hey guys I've been trying to figure out this misfire for a little while now and i'm honestly stumped. The car never missed before, then it came out of nowhere. It throws codes for cylinders 4 and 6. I pulled the plugs and they were wet with gas. I replaced them, the miss was gone for a short bit but it came back, as expected. I've checked for vacuum leaks. Obviously the car is getting fuel if the plugs are actually wet. When i say this I mean the actual electrode. Cyl 6 was black btw idk what that means. My valve cover gaskets leak the slightest bit but its nothing that would be affecting the connection between the boot and plug, its not that much oil. Does anyone know what else I should be checking? Thanks

Lexusdk

Is250? Is350?

if it's an IS250, has the vehicle had the top engine clean? Updated pistons and rings?

Jerkey

Sorry, its a 2004 is300. I've never had the engine itself apart but have only owned for 25k miles. I haven't done a compression test so I'm not sure about the rings but it always ran fine..

Jerkey

Also, the car doesn't ever consume or burn oil so I'd imagine its not slipping past the rings..

Lexusdk

My fault, I wasn't paying attention to the section you posted your thread. IS250 was 06-up.

however I'd check to see if you have any codes besides misfire. Cam sensor or crank sensor code?

next check to see if you have spark on those cylinder. Possibly a bad connector or bad coil. What if you swap the coils with a good known one from a different cylinder, will it change misfire?

Lexusdk

I had one where a crankpulley tooth was accidentally chipped/broken from a timing belt service, and it threw the timing off. In result, causing a misfire

Jerkey

Thanks for the replies DK. I appreciate the help. The first thing I did was swapped the pack for 3 and 4 with 1 and 2. The car still misses on 4 and now 6 as well; make me think its not the coil. I know the car has spark because when I put new plugs in today, it was fine for a couple miles. I'm concerned with the plugs being wet; I need to figure out if this is a result of the misfire or if its causing the plug to foul, then misfire. I'll check the sensors but do you think they could be related to the fouled plugs? I did rear end someone a few weeks ago on the passengers side... The misfire happened right after that as it sat until I fixed my frame. I wasn't sold on the irony.

Jerkey

It has had codes for a long time now since I have catless headers. Since the misfire it also threw a system too lean but I think that's just a result of the unburned fuel

Lexusdk

its possible. Maybe from the accident, it caused the engine to shift and break loose a vacuum hose, kink in the fuel line or jump a tooth on timing (all just speculation). I'd check the timing. Double check all your vacuum lines to the intake manifold. Go back and double check your fuel lines. And actually perform and visually inspect for spark on those bad cylinders.

Jerkey

So I swapped out the MAF sensor with another one I had and it seems to be okay... It was missing at first but I think it cleared up once the fuel burned off the plugs....