iregular hunting at idle

[chapman-s13]

having a bit of difficulty with the old sr today

recently had to do an engine swap (sr to sr)

and now the idle seems to be very irregular tried a search but it threw back hunting between 200rpm and 1000rpm mine is hunting between 1000rpm and 2000rpm and very pulsating it doesnt level out it just cant decide where it wants to be

ive swaped everything from the old engine to the new z32 maf, idle control valve, throttle position sensor, cas litrelly only swapped the head and block everything electrical that was working fine previous is on the replacement engine?

any ideas?

afr's are reading between 15.8 - 16.5
its custom mapped on power fc (no controller to check settings)
the 740 injectors were left in the rail in the greddy plenum just bolted straight to the head...

im yet to grab a compressor to do a boost leak test but from experiance a boost leak makes the car want to die not rev up??

anyone had this before??

[hooky]

Sounds like you have an Air leak around the plenum somewhere, particularly as the AFRs seem lean. Or possibly the IAC faulty?

[chapman-s13]

iac??

right thats cool i can deal with an air leak just need to borrow a compressor then lol

[hooky]

IAC= Idle Air Control valve, its the lump that sticks out of the plenum (above injector 3/4) with two electrical plugs.

Try spraying some Carb cleaner around the plenum when idling, if it changes rpm for a few seconds then its defo a plenum leak.

Pressurising the whole the inlet system will 'boost-leak-test' the intercooler pipes etc, but i suspect your leak is after the throttle body.