help please

[hoffmanvp3]

hi guys im new here as i just bought myself a 2001 impreza wrx and 1 week later i have a problem thats just accured.

when im in the boost the car feels like its missing a few beats,not quite missfiring but loses power for a split second and then back on the boost and then the engine light started to flash and is now staying on.
the car is standard apart from a cat back system and dump valve.
now when i looked under the hood i heard rattling coming from the dump valve.
when the cars idling the internal valve is not on seat but rattling up and down.
my question is:
would this dump valve be causing my boost problem and is that valve meant to be on seat when idling?

your thoughts would be grateful.

thanks

[shambles]

is it a bailyes dump valve - frequently leak. Standard subaru part is better

[hoffmanvp3]

Its a TURBO XS

[shambles]

id would think the diaphragm has broken. Get the standard one. The ecu see air in the engine which you have just vented to atmosphere with a dump valve causing the car to run rich when you floor it again - not good. Cheap one are rubbish and frequwntly cause problems

[Tidgy]

sounds like either a boost control issue or possibly a missfire, need to find out what the code its kicked up is, sounds like one of the sensors is on the blink and that will be your issue.

[hoffmanvp3]

Hi guys. Thanks for all your help. But as of today the car is running totsweet 
I took it to a mate with a diagnostic comp and cylinder 1 was the culprit. Pulled out the plug to find that the ceramic was cracked. A quick change and all is well 

[hoffmanvp3]

Forgot to mention that I also rebuilt the dump valve and greased it up and is working better now. I guess u have to clean them from time to time