2.2 dti overboosting

[wingi]

hi all i have a 2.2 dti signum auto 116k on it. i bought it in march last year and it drove ok until august when it went into limp mode whilst towing coming up with over boost condition. switched off and all was ok for a while then intermittantly over boosting till three weeks ago when it went into limp every time i tried to accelerate! So to start diagnosis i went to check boost control solenoid found it to be hot and when i tried to remove vac pipes broke the union off (heavy handed **** that i am) tried to apply vac to unpowered solenoid no vac powered up still no vac! bingo sorted! or so i thought! fitted new and rd tested now no boost at all!!!!!! head scratching. checked actual data no boost sensing on map cleaned still the same. replaced and yes still the same. now back to basics right start again! connected boost gauge to vac system started and found vac at 3 psi!!!!!!!!!!! wtf, seems v high to me now disconnected pipe from vac reservoir rd tested now boosts better only problem is throttle control deviation not quite enough vac for it. my question is does the vac reservoir control the vac pressure and what should the vac pressure be?

[DTi Elite]

I had a bit of bother recently with a 2.2 & for testing purposes I connected a pipe from the vac pump to the boost solenoid & from there to the turbo , just to eliminate all other pipes , it ran fine so then checked all other pipes & found one split on the inside of an elbow where the pipes connect to the 2 solenoids on the slam panel .
fixed that & away it went , sorted .

[wingi]

if it was a vac leak why would taking pipe off of vac reservoir make the turbo work? i think i have too much vacuum which the solenoids cant disipate quick enough when required thats why i need to know what regulates the vac hence limits the vac pull!

[Signum-Steve]

ok so what your saying is that when booted/towing you go into limp mode. The first thing I would have done is check all of the vacuum pipework for splits and cracks. take a good look at the rubber connectors as these perish over time. The one that fits onto the turbo actuator gets hot so this can become hard and brittle and crack. once you have ascertained that the vacuum system is ok. Check your boost pipework for splits. These can be very hard to detect as the Boost/inter-cooler pipework expands when under boost. Get someone to rev the engine while you take a look,feeling and listening for splits/air escaping.

[wingi]

ok i have already checked all vac and boost pipe work. i have smoke tested all pipes no leaks i have inflated pipe work between turbo and inlet no leaks. i actually think i have too much vacuum in system as apposed too little. the fault i now have is no boost!!!! excessive vac to vnt actuator vanes closed hence no boost!!!!!! if i remove pipe from vac reservoir car runs ok again too much vac!!! i need to know what should limit the vac pull

[wingi]

does anyone know what vacuum the control system should have?

[wingi]

does anyone know what vacuum the control system should have?

has anyone got access to any tech data for vacuum system? i have rd tested car with a gauge fitted in system and under normal (non boost conditions) the vnt actuator has 3 psi of vacuum. when accelerated vnt vac drops slowly down towards 0 but car flags eml on before boost is applied!!! code is p0100 maf reading deviation. tested maf all ok tried new bosch unit just in case. with pipe removed from vac reservoir vac is 2 psi and car runs ok and boosts with intermitant code for throttle valve deviation! (i think throttle is fubar has axial play) i think that with reservoir disconnected vac is too low and connected too high. I need help with the data for this vac system please!!!!!!!!!!!!!!

[DTi Elite]

check the vacuum pipes to the throttle flap on the top of the throttle body , could be losing vacuum from there .