Blow off valve not shut during low throttle

[CaptainHummus]

The title basically says everything.

I was driving one day and experienced a sudden loss of power and started hearing air leaking when I got on the throttle so I expected it to be a blown charge pipe. I checked all my boost connection lines and everything seems to be all nice and tight.

I decided to go WOT to check and see if it was another issue and then my boost levels returned to normal and I was able to pinpoint it to my BOV. It doesn't close until around ~1-2 PSI and after that it works like it should. When the BOV vents to atmosphere the problem "resets" and the valve stays open until around 1-2 PSI again. Normally the valve is always closed and only opens when you get off the throttle.

This results in a very long lag because the boost pressure can not properly build unless the BOV is closed. I think it might be an electrical issue because the BOV is functional but not functioning as it should. I loaded different maps on my AP to see if it was a specific tune that was causing the issue but that didn't fix the problem

What do you guys think?

Edit: Important to note that there are no error codes or error lights

 

[TyphoonFiST]

Incorrect the BOV is always open....but when you step on the throttle it closes and when you release it it opens. it is normal to be open until you apply vacuum to it to close it to build boost.

 

[CaptainHummus]

Ahhh that makes sense. I misunderstood how the BOV behaves during idle or cruising.

The BOV is supposed to be closed when I get on the throttle but it isn't unless I REALLY get on it. Could it be a problem with the vacuum tube then?

 

[thecman02]

I guess part of the question is what BOV do you have? Lots of them have maintenance you are supposed to do. If the seals get dry the piston will start sticking creating the issue you have.

 

[CaptainHummus]

I have the OEM one. Would I have to remove it and clean it out then?

 

[TyphoonFiST]

I have the OEM one. Would I have to remove it and clean it out then?

The Stock setup is a BPV/ Bypass valve and most Aftermarket are BOV's/ Blow off valves. Very similar though in operation...Do you have a BPV spacer?

 

[CaptainHummus]

I do not; I haven't touched the BPV system since I got it. I was thinking of getting an aftermarket one with intentions of fixing the problem but I'm not sure whether the BPV itself is the problem or something else within that system

 

[thecman02]

I have the OEM one. Would I have to remove it and clean it out then?

Oh sorry. I guess if you have a stock bpv and no spacer there really shouldn't be any issues. Any trouble codes?

 

[CaptainHummus]

Oh sorry. I guess if you have a stock bpv and no spacer there really shouldn't be any issues. Any trouble codes?

Surprisingly there are no codes and I even reset the ECU and checked the codes again with my AP

 

[Dialcaliper]

The stock bypass/diverter valve (not really a “blowoff” valve) is also a progressive valve, not a traditional “on-off”valve, so it does not snap open or closed, which in addition to the electronic solenoid wastegate helps with smoother transition from off-boost to boost in part-throttle behavior between making positive pressure and reaching the base 5.5psi wastegate spring pressure. That’s also why the stock valve doesn’t make much of a “kshh” sound compared with old school BOVs.

A traditional on-off BOV valve with a traditional stiff spring mechanical wastegate tends to produce a similar “on-off” behavior - as soon as the BOV closes, boost at the turbo builds to wastegate spring pressure (which is usually higher without solenoid control), and is then throttled at the throttle butterfly, whereas newer electronically controlled cars keep the throttle plate wide open and progressively control boost at positive pressure.

That said, your bypass valve could still be malfunctioning if you are experiencing a loss of power - a vacuum leak to the valve, a bad solenoid, or a sticky valve might cause the abrupt behavior. It could also be something completely different - wastegate, wg solenoid or throttle.

What tool did you use to check for codes?

 

[CaptainHummus]

I used my accessport to check for codes. Although there aren't any that are showing up, there is something that is definitely wrong with the boost system. I checked all of the boost lines and the only source of leak seems to be coming from the BPV. Its not even a constant issue; everything works perfectly once it build 1-2 PSI of boost pressure

I think my plan is to replace the BPV with an OEM one to see if it solves the problem. Where would I need to look to see if the vacuum line is sucured properly before I order the part? It could be a simple fix if this tube just came loose.

 

[Dialcaliper]

I used my accessport to check for codes. Although there aren't any that are showing up, there is something that is definitely wrong with the boost system. I checked all of the boost lines and the only source of leak seems to be coming from the BPV. Its not even a constant issue; everything works perfectly once it build 1-2 PSI of boost pressure

I think my plan is to replace the BPV with an OEM one to see if it solves the problem. Where would I need to look to see if the vacuum line is sucured properly before I order the part? It could be a simple fix if this tube just came loose.

The BPV doesn’t have a vacuum line directly to it, it’s built into the turbine housing and uses only a solenoid for control. It’s pretty easy to remove (one plastic cover over the engine pillows in the wheel well, and 3 bolts plus the electrical connector on the BPV. Just take it off and check if it’s sticky or has obvious wear marks.

if there’s a vacuum leak it would be somewhere near the intake manifold

 

[CaptainHummus]

Awesome thanks for your help! I'll do that this weekend and report to you all what I find

 

[CaptainHummus]

So turns out the electrical harness connection was loose. I plugged it back in and it worked like a charm. When I went back on the road, the problem occurred again when I went full boost. I jacked up the car again and sure enough the connection was loose again.

I don’t understand how any amount of spirited driving could loosen this connection. Maybe the pins on the connection were bad or something. I tried using tape to secure the connection but same thing happened when I went WOT again. I’m thinking of using some epoxy or glue to permanently secure it by I’m worried that it’ll mess up the connection.

it might be important to note that I am running a tune by dizzy so the boost pressure is higher than stock but not by much (25-26 PSI)

 

[Dialcaliper]

So turns out the electrical harness connection was loose. I plugged it back in and it worked like a charm. When I went back on the road, the problem occurred again when I went full boost. I jacked up the car again and sure enough the connection was loose again.

I don’t understand how any amount of spirited driving could loosen this connection. Maybe the pins on the connection were bad or something. I tried using tape to secure the connection but same thing happened when I went WOT again. I’m thinking of using some epoxy or glue to permanently secure it by I’m worried that it’ll mess up the connection.

it might be important to note that I am running a tune by dizzy so the boost pressure is higher than stock but not by much (25-26 PSI)

Thats fairly odd - might be worth inspecting the connector to see if one of the locking tabs has broken off, or if any of the pin contacts are damaged or contaminated. I would not glue it together in case you ever have to take it out, the car’s wire harness side is difficult to replace.

The connector popping loose is probably less related to boost level and more to do with increased vibration of the engine under full power

 

[Intuit]

If the plug and jack no longer snap together and stay together then it is broken.
Wire harnesses can sometimes be taken apart and replaced independent of the wires; releasing the pins can be tricky/frustrating.

Are the OEM tie-downs missing or unsecured?
Is it in a position where it could be affected by a damaged engine mount?

 

[CaptainHummus]

The connection still snaps together with a tactile click but there is some play to it even after it snaps into place. When the connection is loose I don't mean its dangling there completely unconnected; it just isn't pushed in all the way.

I'm not too sure what or where the OEM tie-downs would be. All my motor mounts are in good shape.

 

[Intuit]

Either the gaskets are damaged or pushed out of place or/and some (pins) were misaligned and have been pushed out of position.

 

[the duke]

Just glue it.

 

[TyphoonFiST]

I VOTE for replacing the connector! Time to test out your Electric repair skills!