I have a question 4 my son...

[taco1]

He changed a motor out of his 94 gt was a 3sfe and put in a 5sfe, all is good , until its time to register the car and go through emissions, he failed with high nox, and his cel is throwing a 25 for a code, too lean, he's monkeyed with alot of the obvious fixes, but is still throwing the code and he is wondering now......................
does he need to change the ecu????
could the old ecu for the 3sfe 2.0 be causing a high nox condition with the 5sfe 2.2 ???
Thanks for your help.

[Pineapple]

High NOx is due to high combustion chamber temp. Check timing and spark plugs. Did he add any "mod" to the engine? Like aftermarket performance "chip"?
Also check coolant and rad fan.

[Stevo_Echohb05]

EGR closed?

[dead_Star04]

excess NOx tends to be a bad egr valve. check it for proper operation, and for leaks. iv seen motor swaps where the motor came from japan, where they didnt have an egr valve

[Vip09]

Does anyone else find it strange that the engine he pulled out (3S-FE) wasn't used in the Celica since 1989?? What was that engine doing in there in the first place?? It's supposed to come with a 5S-FE to begin with.

[Pineapple]

It depends on where he is. Anything could happen in Asia.