Cfauvel

Are the transmissions in the IS250 and IS350 the same? As in , are the parts listed the same for the IS250?

P0303 means a misfire on cyl 3. I'm new to any Lexus IS250, so you'll have to find a cylinder number diagram to find out which side and what location the #3 cyl is . The misfire can be a host of things, but a few of the usual suspects are Spark Plug (doubt it) Coil (most probable) Injector The easiest thing to do is to clear out the codes and move coil #2 to position #3 (and vice-versa) and see if the PO3xx moves to P0302....If it does that means the coil is bad. I highly recommend to getting an OEM coil or high-performance coil as some aftermarket coils jus don't cut it. Report back after that test.