less boost after wastegate adjustment Topic is solved

j-john20 · Post by **j-john20** » 03 May 2011, 10:47

its square-2.4 lpt, mines the 12.5 kpa

Post by **JDS60R** » 03 May 2011, 11:12

I would prefer the engine number off the side of the cambelt cover or the vin

A little theory to help others coming late to this discussion.

Underboost is a condition that can be caused by several issues including:

Bad TCV
Bad Turbo charger
Failed boost sensor (for models that have them
ECU seeing overboost and cutting back until reset and condition remedied.
Failed MAF (for ecu's that use the MAF to determine boost pressure)
Failed atmospheric sensor ( again for those that use it)

Generally diagnosis starts with the most dangerous test which is disconnecting the wastegate (yellow) line and installing a boost gauge. If the turbo can quickly make the boost pressure the car requires ( don't go over normal boost level or engine goes boom and wallet gets very thin) then we can assume the turbo is ok. If it was slow to reach the boost level then check the turbo and its hoses for leaks. Also check the wastegate adjustment to be in spec with the info above.

Next is the turbo control valve and its hoses. It is best to replace the TCV with a known good one. You must check the lines and make sure you have no leaks .

Next is a reset. Disconnect power to the ecu and let is reset its adaptations/program. It will take a little driving to let it reset. I take a few short trips and let the computer do its thing.

Next you can check the other sensors. Reset the computer if you replaced any of them.

Finally look for an altered set up. Some owners put unspecified turbos , blow off valves etc on the car and instead of varying the tune to compensate they use all sorts of other measures like bleed off valves , electric/manual boost pressure controllers etc. With a Volvo the idea is to return to stock and build your way up properly.

There are many other things that can happen including failed CBV's that let the pressure leak out , engine problems etc.
Be patient and methodical and you will find it.

j-john20 · Post by **j-john20** » 03 May 2011, 11:39

alright thanks-the car was running so good before i messed with it- i wish i hadnt now believe me- its hard to believe its not an adjustment or something , if i did want to check the pressure -yellow hose off and boost gauge, would i connect the boost gauge directly to the wastegate or just take off the hose and monitor my boost gauge inside the car.

Post by **JDS60R** » 03 May 2011, 11:49

The gauge must be hooked to the manifold after the turbo and throttle plate

It could very well be an adjustment that forced the ecu to back down of the pressure it allows. I will add that in above in the appropriate spot.

j-john20 · Post by **j-john20** » 03 May 2011, 16:23

thanks to all for the help ill look over the basics again and then wrap it up and live with it-ill close this thanks again.

j-john20 · Post by **j-john20** » 03 May 2011, 22:13

hey one last question, im gonna check again for any vacuum or boost leaks in the whole system how would i do this ? in sections maybe hooking up pressure to wastegate and test then manifold and test for leak down and then what or can i just hook up to the wastegate and if no leak down then that means i have no leaks in the system-the reason i ask is if i accidentally hit a vacuum line when replacing the others and cant visually see any broken hoses thanks in advance.

Post by **JDS60R** » 03 May 2011, 22:33

The best way is to remove the lines and check them individually.

Because this is hard to do you can

Test the wastegate from the TCV connection and watch for any of the pressure bleeding off.
The blue line goes to the intake pipe as a return so it almost doesn't matter
The red line is coming off the compressor and can not be vacuum checked. I try to use a pinch clamp to seal the line before the compressor and then apply pressure to it.

To test the intercooler/turbo piping you need to pressurize the line with a plug/stop in the pipe before the throttle body.
There are lots of examples of this on Youtube .

j-john20 · Post by **j-john20** » 03 May 2011, 22:47

alright thanks i just put a bit of pressure again on wastegate and got a little bleed down but not from the line so maybe something inside the wastegate? or the cbv?

j-john20 · Post by **j-john20** » 05 May 2011, 14:06

i am pleased to announce i have solved the problem ,the boost gauge i was using was leaking slowly and inaccurate when setting wastegate,i bought a blood pressure cuff and modified it -160 mmhg = 3.0 psi i set the wastegate and got full boost back also my low end spool up is instant im thrilled and thanks again to all for the kindness and help. god bless.

Post by **Juan62** » 05 May 2011, 18:57

Questions regaring the new IPD TCV instructions: (98 S70 T-5M),

#3. Drive the vehicle for 5 minutes without developing and boost pressure (huh)? What does this mean?
Accelerate the vehicle to approx half of its max boost level and hold there for 5-7 seconds, then decelerate to below 30 mph. Repeat this 4 times. Turn the engine off and wait for 12 minutes...for optimal results, the above procedures should be performed twice.
What is half the boost level? Please advise!!!!!!!!!!!!!!!

less boost after wastegate adjustment Topic is solved

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