i am working on a 1988 4runner had no engine i put a good running motor from another toyota in it.it sets a code 51-52 and pops/hesitates when engine light comes on within 2minutes of running.mass air flow sensor tested within specs just put a new TPS on it due to the old one not being in specs.the motor runs perfect at a idle when you try to exellerate it hesitates and backfires through the intake.i noticed when you start it it runs exellent revs up no popping but as soon as the engine light comes on it pops/backfires.the engine is 22re i have been trying to figure this thing out for months now i really need it gone.the code 52 is knock sensor due to the block not having the hole 4 it so it is diconected.(i was told knock sensor would not cause those problems) the code 51 is signal switch all my book shows is. ac switch checked ok, ac rectifier switch tested ok,tps circuit wich all voltages meet the book specs,TPS is brand new and set to toyota specs,and the ECM.i have nothing telling me how to test the ecm to see if it is good or bad every toyota person i have talked to say the ecms dont fail.and i dont know were to go next.it is a customers truck so i cant just throw money at it.plus i WANT to know why this is happening.any 1 that can help or have any suggestions i would really appriciate it.please toyota techs help

were are the toyota guys.update so i tested coil checked ok for the heck of it tried another coil and igniter from a running truck same thing.tried new wires and plugs due to his being fouled/black still the same.i pulled the ecm and you can tell someone at 1 time swamped it covered in choclate milk mud tried tap testing nothing changed.so if anyone can tell me how to test the ecm that would be great or if i can take it somewere to be tested let me know.since i put the new throttle position sensor on it starts popping/backfiring when vehicle hits operating temp.before it stumbled within 30 seconds of starting motor.any help apreciated thanks

thanks everyone on the forum that helped.found the cam timing was off 3 teeth.whoever did the last timing chain on it did not know how to line up the dots.corrected and now no pops and burns tire.thanks

Wow, I totally missed this thread somehow :shakehead

Glad you got it worked out.