Boost hits 20psi.. then drops to 0

[dynatos]

it sounds to me like something is leaking...like it spools and at a certian psi something gives and cant handle the psi but it's obviously something small....check all ur piping connects...

So if there, say, was a tear in a line or something, you think at 18-20 psi there is enough boost to open a cut/tear/break and enough vac pressure to keep it like that.. then he lets off the gas/shifts/whatever and vac pressure changes, putting the line how it was?

When you figure this out, please let us know what it is - definitely interesting.

 

[dsm_eclipse]

sounds like a boost leak to me try replacing the silicone hose for the mbc. then if that dont work bring it somewhere to get it checked out. somthing like that cant be good at all dsm:

 

[Patterson]

You may be getting a boost spike due to engine knock. If your ecu detects "Knock", it will prematurely open the wastegate to try to save the engine from detonation. There may be a couple reasons your experiencing this problem. Save yourself the headache and take it to a good mechanic. Good luck.

 

[ALL4thaN0okie]

thanks for all the replys guys...

in response to the ECU controlling the BCS its being bypassed now..due to mbc...

i think taking it to a mechanic is the next step.. although i'm afraid... due to my modifications i'm not sure if anyone around here knows how to deal with a modified dsm... think a place like buschur would look at it?? (2 hours away) or should i not bother and just keep it local

or..if anyone knows of a good place around columbus ohio i'd appreciate it..

thanks again for everything

 

[Lazer RS]

You may be getting a boost spike due to engine knock. If your ecu detects "Knock", it will prematurely open the wastegate to try to save the engine from detonation. There may be a couple reasons your experiencing this problem. Save yourself the headache and take it to a good mechanic. Good luck.

Patterson is on the right track here.. Since its pulling hard and holding boost up to 20 then mysteriosly it drops with no stuttering or anything it would have to be something with the Wastegate and BOV. The BOV must be in on this too, because he can again build pressure... just my .02

 

[AllWheelPeel]

I just got the Colt running today. After fixing the three afore-mentioned problems
the car is running fine.
I also removed and cleaned the throttle body and adjusted the throttle pos.sw. and idle
pos.sw. Now the idle is a steady 750rpm instead of 1500. I believe TB cleaning should be considered S.O.P. on these cars.

 

[psychlow]

If you can post a log of a 2nd gear pull and a 3rd gear pull, that'd help us out in diagnosing the problem. Log RPM, injector pulse, timing advance, and airflow.