2G Feels like boost leak should Boost come from BOV vacuum line

[2ggst1998]

So my gst has been having problems with stuttering under hard boost, i got the codes read and they r p0505 and p1103. Also under the car theres a sensor with two vacuum lines disconnected. These r the ones thanks

 

[2ggst1998]

Ya i have it secured now, but the reason i ask is because my car stumbles at 4500 rpm, and when this line pops off the car doesnt do that anymore. So im at a lost rn. When it pops off the idle is terrible but m car wont feel like it hits a wall

I have a small boost leak from the biss and the bov, but i dont believe it should cause the car to stumble that hard

Anybody have any clue, i cannot get an answer to this and i dont want to tear everything down.

 

[briansmith]

Use fuel injection clamps on the vacuum lines holds them on at high boost. Any boost leak will cause a problem in some form, you are losing metered air and the ECU does not know this. Small leaks will cause inaccurate fuel delivery. While larger will cause rich conditions leading to fouled plugs, flooding, and misfires.

If your MAF reads x air flow and there is a leak that seeps 20% of it after the MAF. The ECU will deliver fuel for x, not x-20%. Now you are rich. Fouling plugs.

If you have leaks. Fix the leaks and check the plugs. Non turbo cars only run in a vacuum leaks cause these cars to run lean. Turbo cars run both ways vacuum and boost, so you can run lean and rich with leaks.

 

[2ggst1998]

Ok I understand all this thank you, but why would the car perform properly when the BOV vacuum line pops off?

 

[TehRiceBandit]

I read your other post. Fix your CELs.

Code P1103
P1103 Turbocharger Wastegate Actuator
http://www.dsmtuners.com/threads/check-engine-light-code-p1103.266803/
http://www.dsmtuners.com/threads/cel-code-p1103-turbocharger-wastegate-actuator.250803/

Code P0505
Idle System Malfunction
-Probably from when your BOV vacuum line blew off.

 

[TehRiceBandit]

Ok i understand all this thank you, but why would the car perform properly when the bov vacuum line pops off?

Your actuator is sticking open causing over-boost and giving you fuel cut. When the BOV vacuum line is off your BOV is open all the time preventing you from over-boosting.

This is just my educated guess. I may be entirely wrong, if so someone please correct me but that's my understanding.

 

[2ggst1998]

I understand that and I will look into it, but why would my car work fine with that hose disconnected. The CELs are there and the car will work fine with it off

Doesn't the BOV stay closed. When the line is disconnected my car will flutter. So it seems as if it is stuck closed. Also do you mean the wastegate is stuck open?

 

[rough]

Sounds like maybe your vacuum lines are run wrong... or are leaking badly. Have a picture of your setup?
When did you start having this problem, was it after you modified something?

 

[2ggst1998]

Thats what i thought, the only thing ive done since i got the car was downgrade the car. It was like that when i bought the car. It came with greddy ic piping, greddy bov, greddy intake, and mbc. I took the mbc off because i thought that was the problem and i hooked up the wastegate solenoid. Ill take pics soon and put it up

 

[briansmith]

The BOV should stay closed with the line off till boost hits spring pressure then boost will open the BOV. But given the BOV line is off at this time I highly doubt the vehicle will ever boost enough to do that. Now the car preforms correctly. No. Lol

With the BOV line off is a gross boost leak. This leaves somewhere for the boost to exit. If you have a wide band it would show a big rich problem under boost what boost pressure is the car hitting on a pull and what happens when the line blows off?

I think a lot of people are confused on how BOV's and wastegates work.

The bypass valve is normally closed due the the spring pressure this holds the BOV shut but not well enough, the reason for the vacuum/boost line it 2 fold. Under boost above spring pressure boost fills on top of the diaphragm helping the spring.

When the throttle plate closes between shifts and boost turns to vacuum the line then vacuums above the diaphragm and overcomes spring pressure opening the valve. This is the only real reason for the spring. Wastegates work in the same way. Just reversed vacuum helps the close and boost opens MBC bleeds off set psi to reach higher boost psi than the spring can handle. But if exhaust pressure surpasses spring pressure the flap will creep open no black magic just good old mechanic theory.

The most important thing when coming to turbo cars, vacuum lines run both ways, vacuum under vacuum and boost under boost. N/A cars only run vacuum.

I think this is a concept some people over look when moving from 1 car line to another and why boost leaks cause so much problems. Some leaks will hold vacuum because it's suckling the seals in. And there may be something there that helps the sealing like a lip or boss around the injectors. But under boost these seals get pushed out with nothing to hold them in place.

Remember the KISS method. Don't over think things and. Keep It Simple Stupid.

 

[2ggst1998]

Wow what a response thanks, but i cant find any problem im just gonna get a 14b turbo and see if that does anything cause i got my self a good deal on one, im thinking its my wastegate actuator. But ill let yall know what happens tomorrow.

 

[Priority DSM]

Also have you reset your ECU after the downgrade? This will reset your fuel trims. I don't know if it will really help with any of your issues but anytime I change engine parts on my car I do this.

(Unplug battery then turn on head lights to drain all power. Reinstall battery terminals)

When you fire up your car for the first time after the reset,turn on headlights and heater/blower to max. Let it idle like that until it reaches operating temp (needle at center of temp gauge).

 

[briansmith]

It's not actually resetting fuel trims. It only clears save info of the LTFT. STFT is how the ECU is reacting at that moment to correct the trim to hit the target AFR in closed loop. LTFT shows how the ECU has compensated over a span of time to hit the target AFR in closed loop. These numbers are useful in seeing what the ECU is doing, adding fuel for lean conditions or subtracting for say a boost leak.

The primary input for these trims is the upstream O2 sensor. Unfortunately 1g and 2g computers do not have adaptive learn capabilities, meaning the computer does not learn anything other than IAC position as the throttle gets dirty. New cars like the Kia and Hyundai even Mitsubishi have adaptive learn logic. Meaning the car learns the drivers habits. This can change anything from engine response to shift rpm and firmness. Very cool technology I learn working for a dealer.

 

[2ggst1998]

So update guys, i went to pick up a 14b today, ended up with a 16g with 650 injectors, gonna hook this all up and let yall know whats going on

 

[2ggst1998]

Im running stock boost, and when the bov line popped off the car could rev past the point it would stumble, but it would idle terribly

 

[synthetek]

So update guys, i went to pick up a 14b today, ended up with a 16g with 650 injectors, gonna hook this all up and let yall know whats going on

What are you using to tune with?

 

[rex4g63]

Not going to bother reading all of these post to much o. Your stumble....Check out your Mass airflow sensor and make certain your connector is pushed in all the way and secured by the clip. Check air intake that clamps are tight and there isn't any unmonitored air getting in. If u still have the problem than u have a vacuum leak look for any rotted or Crack vac. Hoses. Good luck

Your BOV and stubble are probably 2 different things unless u are venting to atmosphere. Forgot to mention even a substantial boost leak may cause a rough idle and stumble. Especially if you have you MAF in stock location and haven't relocated it to your IC piping

 

[2ggst1998]

Ya my mass airflow sensor has been cleaned, and the i take is on there nice and snug, but i have ecuflash but with the 16g on im not planning on running high boost rn im just going to see if it fixes the problem, if it does than ill go an ahead and raise the boost

Nope bov is not atmospheric and how would u relocate the maf? U dont have a fmic i just have ic piping but the stock smic

* sorry i dont have a fmic

 

[rex4g63]

I used to blow intercooler piping apart when I ran high boost on a 20G. WHEN The intercooler came apart car would always stall leaving me stuck on the highway. Purchased a GM MAF and maf translator relocated to IC piping.

Your problem however sounds like you have a vacumm leak tho. Also if your engine is stubbling another good thing would be to check your plugs and plug wires. I had a heavily modded GSX when I was 19 and experienced something very simular almost felt like it was fuel cut......what it actually was was the insulation had broken down on the plug wires and we're arching out to the head causing some violent miss fires when accelerating. This is going to sound stupid to u but one night go to a dark location and open your hood while the engine is running. I could actually see the arching even at idle which case something almost identical to what you are explaing. (Not referring to you vac. Line coming off your BOV tho)

 

[2ggst1998]

My plugs and wires are brand new i did think that it was that, but i believe its my wastegate actuator

 

[95_gsx_2g]

It's completely normal to have boost in the blow off valve line, most likely your blow off valve is fine. Many things can cause a stumble or misfire but make sure to zip tie all connections tight such as the boost controller and waste gate and blow off valve line to ensure there is no leaks. What he is referring to by relocating the mass air flow is a speed density conversion. This includes a map sensor and internal air temperature sensor and something to tune with that has the feature like link v3.

 

[rex4g63]

Could be but I think it would be unlikely to cause what u are experiencing. The the waste gate failed to open u would mist likely over boost exceed your fuel capacity and get fuel cut. If the waste gate remained open and or you have a large fracture near the waste gate flap you would fail to properly build boost....your turbo would basically be working over time to build pressure and would eventually destroy itself from excess heat.

Dont rule out the ignition ststem just yet....If you purchased iridium plugs and gapped them you may have fractured or damaged the electrode which would cause misfires under boost and unstable idle. Been through all this crap before so I feel your pain and wish ya luck.