LS400 P0340,stumble above 3,000 rpm
 

DON"T BLAME ME...but an old shop i used to work for installed a 1990 motor in a 1997 LS400 because the original one had a bad knock in it....after they installed the 1990 motor,it ran fine except when you get at or above 3,000 rpms the car falls on it's face (and a P0340 is set)...the original wiring harness was used and the cam shaft sensors have been swapped...i have driven it and it isn't a misfire,but feels like the injectors are shut off like a rev limiter issue...my first question is..what are the differences in these two motors,if there is any?....could it be something like incompatible cams and or cam gears?...different heads?....bad computer?....a 1990 is old school and 1997 is OBDII...is that an issue?...i'm just trying to help them out and find an answer....would installing a "like year" motor work?....any help is appreciated....thanx in advance.....steve elliott owner/opperator Steve's Shop in Louisville Ky

P.S. if you want to know anything else just respnd to thread