1jz missing and backfiring

[corolla.fx-gt]

hey guys this is a question i am asking for a friend of mine. we have recently gotten hold of another 1jz to put into his dirt track car as the other 1jz is burning oil and we need another while we fix it and hopfully get some more power out of it while using the other engine.. anyway we got engine in fine and it runs and car moves and all that but one problem we cant seem to figure out is that once the engine gets all warmed up it doesnt seem to want to rev up asoon as we try reving it, it starts missing and backfiring alot but at idle it sounds mint. its fine when its cold it revs up alright but only starts doing it once warm. we would really appreciate any help on the matter

cheers.

[bgrieger]

Welcome!

A few things to check over:

the throttle position sensor setup?
Cold start injector leaking?
leak in the air intake hoses or in an intake manifold gasket?
is the EGR operating correctly?
bad MAP sensor?
leaking fuel injector?
timing (including the cam timing)?

These are all fairly common things that lead to stumble and backfire. The stumble when you give it gas is often a Throttle position sensor type problem, but check out the easy stuff first.

Bob