why does my boost fall off?

[peterkin]

alright, i've been researching and asking local guys questions now it's time to act.

what could cause my boost to fall, flash, fluctuate and everything else.

here's the deal, when i floor it WHAM it flashes 19-20 psi ( maybe 3* of knock ) and then immediately falls back to 15 psi. how do i get the rock solid boost people talk about? how do i get my boost to creep up in 3rd gear? i wish i had that problem. i can't get my boost up enough for me in 3rd.

my main concern is the flashing then falling though! any ideas.

 

[hot6-231]

There could be a few different reasons for this. First, did you try changing out the boost solenoid on the passenger side valve cover? Had that same problem a few years back. You have to get it at a GM dealer. Could also by a weak diaphram in your adj. wastgate (under turbo). Or, maybe someone replaced the 3 small hose's near the turbo and mixed em up. Other reasons include a cracked header(very common), or if someone installed a gasket under the turbo, the gaskets tend to leak after a few years and could bleed off boost. Hope this helps.
KB

 

[peterkin]

thanks hot6, i also failed to mention that i replaced the ds header but it didn't have a gasket when i took it off so i didn't put one back on. that is in the works though, and my turbo/header gasket is on the way from postons. my wastegate actuator is brand new, not saying it couldn't be bad but i'll check that. i'll try someone elses solenoid and see if that helps.

thanks for the suggestions.

 

[NC87GN]

Hey Peterkin,
Had same problem on clints car. We had it tied into the line running to the evaporator canistor and it would vary just like yours. Try to monitor boost directly from the compressor side of the turbo. Also use some good rubber lines that do not balloon under pressure. HTH

P.S. It could be 3rd and 4th gear boost scalars in the chip, but not likely..

Mike Banas
87GN

 

[peterkin]

i'll do that right now mike, great idea. i can't remember where i tied it into ( probably the vacuum block ), but i'll go check now before i drive to the metro station.