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3rz swap - Rough idle, backfire, stalling and unresponsive throttle

95.5-2004 Tacomas & 96-2002 4Runners 4th gen pickups and 3rd gen 4Runners

3rz swap - Rough idle, backfire, stalling and unresponsive throttle

Old 06-10-2019, 07:26 AM
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3rz swap - Rough idle, backfire, stalling and unresponsive throttle

I have a 85 runner with a 3rz swap that I bought after its been sitting for 8years, Engine doesnt have a lot of miles on it was running perfectly before beeing installed but the wiring was never completed.

once everything was wired The truck started but stalled at every bit of throttle. Only way i can make it rev is by pumping the gas pedal.

So far I did:

Maf sensor ( new )
coil pack
spark plugs + wires
check the grounds and change the battery terminals
removed and clean the throttle body.

nothing fixed it but now the truck will rev up flawlessly on startup but will start runnning very bad or stall once it drop back down to idle rpm.
it want to stall if I give a litle bit of throttle but if I hold the pedal all the way down it will start backfiring like crazy and sometime the rpm will surge and when I let go it will run perfectly for a second then stall again.
Not sure if it is relevent but some backfire look like they may be in the intake tube before the throttle body.

The wiring look sketchy at some places so I can't rule out that the maf is not fonctioning perfectly but im uncertain how I could verify that.
Vacuum leak is also a possibilty but there is no apparent major flaw and its hard to test for leak with propane if the engine wont keep running unless I pump the gas.
Ecu is also showing no code anymore after replacing the maf and the coils so im starting to run out of idea
MikaelT is offline  
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