Engine/Turbo Trouble?

[ovurboost95]

I have a 95 GST 4G63 5 SP. My only Mods are a BOV, Intake, and Boost Gauge. I just installed a new set of NGK Plugs/Wires gaped at .28. Leak test found a few vacuum leaks that I repaired. The Problem I am having is in 3rd,4th.5th gear anything more than 1/2 pedal the car bucks and jerks real bad. If I am in 4th or 5th and floor it, the car has no power, the Boost gauge hits stock boost then bounces around like crazy while the car does the jerking thing. As long as I stay above half pedal (enough to open the BOV when shifting) it runs great. but if I go any harder it is like driving my Cavalier!!! I had it hooked up to a Computer and No codes would come up. anyone have any ideas?

Thanks,
Isaac

 

[Joshewuhh]

Boost leak.
Do a boost leak test.
Checkl around the intercooler piping couplers.

 

[ovurboost95]

I already did a boost leak as stated in my original post. I replaced a few vacuum lines.

 

[PimpDrive]

When you are driving your car in 3rd, 4th and 5th when you bring the throttle to more than 50% is that when the motor is going into boost? is it a electric boost gauge, and are you venting? more specifics please, but it sounds like a pesky boost leak to me also, not big enough to do it in 1st and 2nd, but the under more load like in 3,4,5.

If you have not checked for a boost leak since, you might as well try since it takes but a few mins, and when the intake is off the turbo see if you have any shaft play, in out up and down. if its a mechanical gauge check that too. Pull the plugs and check them too.

 

[Joshewuhh]

I already did a boost leak as stated in my original post. I replaced a few vacuum lines.

Vacuum and boost are 2 completely different things.
vacuum is pressure created by the hydraulic brake booster and run throughout the throttle and engine.
Boost pressure is created by the turbo and run through the intercooler and turbo lines.

the Boost gauge hits stock boost then bounces around like crazy while the car does the jerking thing

Do a BOOST LEAK test.
With the car running, get a spray bottle with soapy water and spray around the turbo couplers, all the lines, the intercooler couplers (inlets and outlets), and if you see bubbles, theres a boost leak.

 

[numlock666]

Sounds to me like your venting because that's what my car does when I vent due to the bov bleeding off some metered air at mid throttle. WOT would be fine, just cruising sucks.

 

[tom04841]

Vacuum and boost are 2 completely different things.
vacuum is pressure created by the hydraulic brake booster and run throughout the throttle and engine.
Boost pressure is created by the turbo and run through the intercooler and turbo lines.



Do a BOOST LEAK test.
With the car running, get a spray bottle with soapy water and spray around the turbo couplers, all the lines, the intercooler couplers (inlets and outlets), and if you see bubbles, theres a boost leak.

DUDE....Please don't post if you don't know what you are talking about. I understand that you are trying to help, but you really aren't.

Vaccuum is created by the motor not the brake booster......vacuum is present behind the throttle plate when not under boost. There is a vac line that goes to the brake booster to assist with braking. A vaccuum leak lest needs to be done with the car idling. Get some carb cleaner, and spray all your vauum lines and intake tube. If idle raises, you have a vac leak

A boost leak test is done with the car OFF. Take off the intake to the turbo. Make a boost leak tester as per this link click here
Then spray all the couplers, ic, etc....to check for leaks....it will bubble.

 

[ovurboost95]

I did the Boost leak test already. Replaces a few hose couplers (Sorry not vacuum lines) and Sealed some others. a retest showed no more leaks, But I will do another one tonight after work. I have the BOV hooked back into the intake so no venting. The motor/turbo spools and boosts normal. sometimes in the morning the spool sounds funny like it's under water. it only sounds that way through 2nd gear. after about 2 minutes it quits. I will also check the turbo tonight for shaft play. The boost gauge is a JDM mechanical. Thanks

 

[tom04841]

Any smoke out the exhaust while driving?

 

[ovurboost95]

Only under really hard acceleration 5-6 grand. Never any coolant loss oil is always clean.

 

[PimpDrive]

The funny under water sound, Does it sound like a low pitched howling noise?

 

[ovurboost95]

It sounds like the turbo is spooling and fluttering at the same time. kinda like someone trying to talk with water in their mouth!!!

 

[ovurboost95]

Sorry it took so long. here's what I found. Checked all the wires, they were good. Checked plug gaps. My NGK's have 2 tips. Upon inspection I found a few out of gap. I pulled all of them regapped at .28 and Replaced a Coil. Car ran A hell of alot better. Still a boost problem. Found a crack in the upper I/C pipe. and a dry rot split in my recirculation hose. replaced both items retested found no more leaks. Let me say I had no idea these cars are that fast in stock form!!!!! Thank you for all the help.

Isaac