Not boosting properly (tested EVERYTHING, can't fix)

Geezer000

Member
I have been trying to figure this out for months now. When I boost it doesn't hit full boost( 8psi) until about 5500-6000rpm. It used to do it at 2500rpm. Every once and a while it boosts great and 2 min later gone.....
Thing I have tested/ replaced:

-did boost leak down test =no leaks (up to 25psi)
-tested BPV for leaks =no leaks
-checked all vacuum lines =no leaks (21hg idle)
-replaced wastegate with ATP (old one leaked) =no difference
-checked wastegate flapper =lined up fine
-checked turbo shaft play/movement =great shape
-checked Boost gauge accuracy =same as SSAFC reports
-replaced cracked manny with Steedspeed = no difference

I even tried unplugging the wastegate to see if it would boost up to 16psi like it should but it maxed out at 11psi and no higher.
I'm at a loss...... :(

Any ideas?
 
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I have been trying to figure this out for months now. When I boost it doesn't hit full boost( 8psi) until about 5500-6000rpm. It used to do it at 2500rpm. Every once and a while it boosts great and 2 min later gone.....
Thing I have tested/ replaced:

-did boost leak down test =no leaks
-tested BPV for leaks =no leaks
-checked all vacuum lines =no leaks
-replaced wastegate with ATP (old one leaked) =no difference
-checked wastegate flapper =lined up fine
-checked turbo shaft play/movement =great shape
-checked Boost gauge accuracy =same as SSAFC reports
-replaced cracked manny with Steedspeed = no difference

I even tried unplugging the wastegate to see if it would boost up to 16psi like it should but it maxed out at 11psi and no higher.
I'm at a loss...... :(

Any ideas?
 
u sure you checked for leaks on the hotside and coldside pipe? like not just the bypass but the little nipple peice cuz it could be cracked.
 
What type of mid pipe, cat or non-cat? When you unplugged the WGA was the 11 psi also extremely delayed?
 
u sure you checked for leaks on the hotside and coldside pipe? like not just the bypass but the little nipple peice cuz it could be cracked.

I checked for leaks using a boost leak test. I plugged the end of the maf with a rubber seal with an air nipple on it and then introduced 25psi and there was a very slight leak at the nipple which I sealed but it didn't help.
 
I wouldn't advise the "removing the vac line to wga test" again EVER!

I still think this could be a wga issue? What are your wot in boost afr's?

Seafoam through the intake can help to track down leaks pretty good too... maybe at the turbo to mani flange??
 
I wouldn't advise the "removing the vac line to wga test" again EVER!

I still think this could be a wga issue? What are your wot in boost afr's?

Seafoam through the intake can help to track down leaks pretty good too... maybe at the turbo to mani flange??

Its a brand new ATP wastegate, I have a wideband and will be installing it hopefully next week. Don't know what the afr's are right now. Would the boost leak test find leaks in the vacuum lines or is that a totally separate entity?
 
Well looks like you looked into everything but the exhaust. The cat may be the next thing to look into.
 
Well looks like you looked into everything but the exhaust. The cat may be the next thing to look into.

So your thinking it could be a plugged cat? Would that cat show any signs of being plugged after a 20 minute drive? Like would it be glowing red?
 
That's why I asked cat or non, possibly too much back pressure from your catalyst. Once the car is warmed up see if the vac remains where it normally does at idle when you raise the RPMs up to 1600 or so. If not that you have a new source to check.
 
That's why I asked cat or non, possibly too much back pressure from your catalyst. Once the car is warmed up see if the vac remains where it normally does at idle when you raise the RPMs up to 1600 or so. If not that you have a new source to check.

So if the vacuum stays at 20ish while holding steady at 1600rpm(unloaded) the cats good? If not its bad?
 
That's why I asked cat or non, possibly too much back pressure from your catalyst. Once the car is warmed up see if the vac remains where it normally does at idle when you raise the RPMs up to 1600 or so. If not that you have a new source to check.


At idle my vac is around -20, when warm and hovering around 1600rpm (no load) it's at -19/-20. No real difference.
 
Well that's not a plugged cat. So unless its a failing turbo its back to square one (connectors, pipes, hoses, BPV or WGA).

Like Shane suggested try a Seafoam treatment. There beneficial anyway and you will notice if smoke is coming from a place it shouldn't.

Here's hoping its something simple overlooked and not the turbo.
 
Well that's not a plugged cat. So unless its a failing turbo its back to square one (connectors, pipes, hoses, BPV or WGA).

Like Shane suggested try a Seafoam treatment. There beneficial anyway and you will notice if smoke is coming from a place it shouldn't.

Here's hoping its something simple overlooked and not the turbo.


I will try a seafoam treatment and see what I can find.thanks for all the help guys.
 
Im having the same issue, mine will only boost to 5psi at WOT and bearly will boost in 1st. But I think I found the problem right in the middle of my exhaust manifold there is a small bearly noticiable crack causing the exhaust to leak out before the turbo its unnoticable when the car is warm because the cast iron is so sensitive to the heat and will just expand and close it just enough so do you dont hear the leak.. are you getting any kind of exhaust leak ticking?
 
Sprinkle some baby powder on the suspected area on the exhaust mani and start the car...you'll see what a presumed ittle crack can let out. Seafoam will do the same but will also help track down vac leaks around the im and injector seals.
 

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