Hey guys! Please any advice would be greatly appreciated. I am a master tech at Toyota and I have this LX570 I'm working on but struggling to find the fault. Long story short, it has a brand new motor fitted. When driving I get message on cluster "engine reduced power, visit dealer" with fault code "P0300 - random/multiple misfire detected" . On the data list while driving it shows cylinder 2 and 4 have misfires (which you cannot feel). Engine is new, spark plugs new, swopped coils and injectors with other cylinders (still misfires showing cylinder 2 and 4), checked wiring from injectors and coils to ECU - all good... Last thing I can think of is either ECU or intake manifold...

Any ideas?

 

Why is the engine new?

Also maybe the ecu is bad was the vehicle jumped backwards, water damage?

 

It dropped a valve so engine got badly damaged and was replaced. I don't see any signs of water damage and as far as I know it was not reverse jump started.

 

just a wild guess: Whatever made the old engine blow a valve, is making the new one act funny? is there some external electronic part that could cause that that you are reusing?
Otherwise, why would a valve fail in a 2017 engine?

 

It's very odd to have a failed engine in a LX. Did you just purchase the vehicle? When you said engine is new (and plugs etc), you mean it's brand new from Lexus / Toyota? Or new as in 'replaced w/ used engine'? Was the engine replaced under warranty (6yr / 70k?), if so there's not much to worry except to get the truck back to Lexus. If the coil packs were swapped and still misfiring at cyn 2 & 4, I would also assume the spark plugs were installed and torqued correctly, look into something 'before' the coils'. If the intake manifolds are found clogged, it is very odd. Check signals from the wirings too (Out from ECU; Before coils).

 

Is everything reading withing spec? Hook a scan tool up to it and let it idle see if anything is not reading withing spec. Then go and drive it and have someone check and see if anything if not reading correctly. I feel there is a gremlin somewhere maybe a mouse chewed a harness? Bad body grounds?

 

OP, as a tech at Lexus, have you involved Lexus engineering yourself or through your boss??