I need help cars acting werid cant figure it out

[mitsugsx99]

i own a 99 gsx just did a motor swap to a six bolt im having and idle sure between 1500 and 2500 and when i rev the car my aem tru boost gage is showing boost is spiking at 38.4 pounds and thats on at 4700 rpm need help cant figure out how cap the boost any ideas

 

[92AWDHX40]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)


this is good for your idle surge, sounds like thats a problem for you.

 

[mitsugsx99]

thanks ill keep reading i jus dont get it before the car wasnt doing this until me and my buddy put the vacuum lines back to stock trying to get it to stop idling at 3500 rpm with the inter-cooler pipe hooked up
but i still cant figure out why the boost is spiking at 38.4 pounds at 4700 rpm tried to lower everything dosent do anything we have tried everything we can think of and as soon as we get some progress it has something else go wrong sucks
and we rerouted the vacume lines back to how they were before

 

[Dsmkauai]

Is your wastegate stuck?

 

[BurrowZ]

Throttle cable.

Throttle position sensor.

Post throttle body vacuum leak.

 

[dalesocks]

what turbo? your wastegate could be stuck open.

 

[BurrowZ]

what turbo? your wastegate could be stuck open.

No.

A wastegate being "stuck open" would result in little to no boost. Not a spike at 38lbs.

OP: Are you spiking at 38.4 in gear or at idle? I would find a cheap mechanical boost gauge and hook it up temporarily because EBCs have been known to fail sometimes.

As for your idle: This is a vacuum related problem clearly since enough air is getting past the throttle body to have it idle at such a high RPM in the first place.

 

[mitsugsx99]

Sorry it took so long to reply been working a lot we double checked all the vacuum lines and there's no leaks any where as for the throttle we've tried to reset it and everything we could do and we tried my other boost gage and its still saying the same ill check tomorrow and see if the waste gate is stuck
But yes the cars acting like this well its idling and then we tried to rev it and boost goes to 38 psi and the car wont go past 4900 rpm I haven't driven it yet what to just to see how it does but at the same time I dont because I don't wanna mess some up