ok i just got a engine swap done for another ka24de motor in my 91 240sx. it was from a 93. after getting it installed there was a slight problem. the first day when the mechanic had turned the engine on he told me it was runing smoothly. he told me there were a few minor adjustments to be done so i decided to pick it up the next day. when i showed up the next day he told me there was a problem so he showed me . whenever he would rev the motor up, it wouldnt go farther then about 2500rpms. judging by the large ( more then normal ) amounts of fumes coming out of the exhaust he said that there might be a problem with the fuel injectors. he then stated that there could be some other problems but he wasnt sure. another thing i noticed when test driving it, whenever the car was idling it seemed like it was about to stall. the mechanic also found a broken ring from the cat if that helps any, but he replaced that. need some help guys thanks.

 

also before i had the engine swapped, i had a bent rod in my stock ka. i just decided to drive it to the shop since i had no cash to get the car towed. as i was driving it smoke started pouring out of the car. i heard from another post that the cat couldve been clogged up really bad causing my problem. hopefully this will help if any.

 

sounds to me like you're running a few cylinders short. same symptoms on my talon. Check to see if you're getting spark. Check the plugs, wires, and coil pack. From there, i believe the ignitor is next, and lastly your ecu.

 

With no load its either that you are misfiring or the MAFS is dirty or busted. Shoot the MAFS with carb cleaner and try it again. Also have the mechanic check the fuel pressure. 300zx's behave like that if the EGR is malfunctioning, I never had that prob with the my old 240.

I assume that the mechanic has already checked for a sticking/faulty throttle mechanism.