new engine build...hanging rpms...please help!!!

[jwhite]

a friend of mine has just finished a major build up (by himself) and is having some issue with hanging revs/irratic revving...

pertinent information: 1996 mustang GT

ENGINE:
-5.0L modular stroker (SOHC)
-AFM cams 202/206 duration
-567th intake and exhaust valve lift
-.315 lift @ cams
-112 intake 108 exhaust duration
-MSD coil packs
-P51 intake
-42lb injectors
-85mm mass air (C&L)
-75mm throttle body

POWER ADDER:
-HP performance twin 50mm turbos (intercooled)

OTHER INFO:
-fidanza aluminum flywheel & spec3 clutch
-SCT chip (set up for engine break in period)


what is happening:
-the car starts and immediately revs to 2200 or so (for about 3-4 seconds) and slowly drops to 1000rpms
-the car idles steady at 1000rpms
-a slight blip to the throttle and the car revs to 2200rpms and hangs and slowly lowers back to 1000rpms
-when driving and engaging the clutch to shift, the cars rpms will shoot to 2300-2500 (on their own...no blip of the throttle)
-when coming to a stop after driving, put the car into nuetral and the rpms will rev on their own to 2300-2500 and hang for 4-5 seconds (sometimes longer) before falling to 1000

any help/ideas are much appreciated!

thanks in advance!

 

[ShortThrow50]

same dam problem im having on my 93 5.0
so far i have changed the tps and the iac
cleaned maf and egr
now im in the process of removing tb and egr and replacing the gaskets
You probably have a small leak somewhere

 

[jwhite]

thanks for the tip!
i will have my buddy double check all of his connections...
i have been doing some reading and some mach1 people were have a similar issue with their IAC...
their fix was to make a sort of restrictor plate to restrict air from flowing so fast thru the IAC.?.

 

[Mongoose 03]

a friend of mine has just finished a major build up (by himself) and is having some issue with hanging revs/irratic revving...

pertinent information: 1996 mustang GT

ENGINE:
-5.0L modular stroker (SOHC)
-AFM cams 202/206 duration
-567th intake and exhaust valve lift
-.315 lift @ cams
-112 intake 108 exhaust duration
-MSD coil packs
-P51 intake
-42lb injectors
-85mm mass air (C&L)
-75mm throttle body

POWER ADDER:
-HP performance twin 50mm turbos (intercooled)

OTHER INFO:
-fidanza aluminum flywheel & spec3 clutch
-SCT chip (set up for engine break in period)


what is happening:
-the car starts and immediately revs to 2200 or so (for about 3-4 seconds) and slowly drops to 1000rpms
-the car idles steady at 1000rpms
-a slight blip to the throttle and the car revs to 2200rpms and hangs and slowly lowers back to 1000rpms
-when driving and engaging the clutch to shift, the cars rpms will shoot to 2300-2500 (on their own...no blip of the throttle)
-when coming to a stop after driving, put the car into nuetral and the rpms will rev on their own to 2300-2500 and hang for 4-5 seconds (sometimes longer) before falling to 1000

any help/ideas are much appreciated!

thanks in advance!

One of the many reasons why I love my carburetor

 

[WhinRR]

same exact situation here. I have been wondering what it was from. So with the things u tried what helped?