rough boost,cut,then full spool,then repeat

[bloodlinebkx]

i have a 98 Gsx eclipse with a 20g, fmic, greddy, BOV, innovator wideband, and boost gauge, my car sometime spools fine in 1st gear, 2nd it hesitant and then after not lettin off the throttle it will boost some times,vacuum reads 18 to 20,so i feel i have no boost leak but my gasket gone on the exhaust side of the turbo along with 3 bolts,and im ready random miss fire,and im replacing my valve gasket to,one is torn. car run really rich when boosting max 11psi it at 9.5 some one please help me i got 2 weeks then school, i need it running smotth before the 3rd

 

[TSicktalon]

I would sort out all of the issues you have mentioned, then see what else needs to be addressed.

pulling good vacuum is irrelevant to boost leak testing. vacuum is from the throttle body into the motor, boost is from the turbo into the motor.

Check your plug gap, check that you are getting good spark. If you are running REALLY rich, you could be decreasing the spark with having too much fuel in the chamber.

 

[bryanwheat]

Boost leak, check for them by pressurizing the intake.

 

[talontd92tsi]

Boost leak, check for them by pressurizing the intake.

+1. I would expect that you have a pretty large boost leak. Everything can "look" and "feel" okay, but until you put a coupler on there and feed the engine 20+ psi of air pressure when not running will you ever track them down. Soapy water is a huge help in finding them too.

Also, make sure that all of your coupler clamps sit perpendicular to the pipe (not crooked). It will not matter how tight you clamp it, it WONT completely seal.

 

[bloodlinebkx]

+1. I would expect that you have a pretty large boost leak. Everything can "look" and "feel" okay, but until you put a coupler on there and feed the engine 20+ psi of air pressure when not running will you ever track them down. Soapy water is a huge help in finding them too.

Also, make sure that all of your coupler clamps sit perpendicular to the pipe (not crooked). It will not matter how tight you clamp it, it WONT completely seal.

clamps are on i had to fix it before, the j pipe from the turbo was too long so i had to cut it and do new smaller clamps and hose.i dont know if it is a leak cause it pulls some times and some times it acts up.but i still have the stock tune.the shop said if i have a weak vacuum then i have a boost leak.is that correct?

 

[bryanwheat]

clamps are on i had to fix it before, the j pipe from the turbo was too long so i had to cut it and do new smaller clamps and hose.i dont know if it is a leak cause it pulls some times and some times it acts up.but i still have the stock tune.the shop said if i have a weak vacuum then i have a boost leak.is that correct?

Just do a boost leak test on it.

 

[bloodlinebkx]

I would sort out all of the issues you have mentioned, then see what else needs to be addressed.

pulling good vacuum is irrelevant to boost leak testing. vacuum is from the throttle body into the motor, boost is from the turbo into the motor.

Check your plug gap, check that you are getting good spark. If you are running REALLY rich, you could be decreasing the spark with having too much fuel in the chamber.

my first plug gap is gone, the rubber from running it when i 1st installed the turbo.it came right out pullin the spark plug wire.and i though boost leak test consist of vacuum check.

 

[TSicktalon]

A boost leak check is when you pressurize the system (turbo->IC->motor) to verify that everything is sealed and doesn't blow apart under pressure.

Think of boost/pressure as the turbo PUSHING air, it pushes on everything, the pipes, lines, couplings, gaskets...

Vacuum is the motor trying to PULL more air in. The throttle body doesnt allow much air to pass in at idle, so the motor is pulling on everything between the throttle plate and the cylinder.

Think about when you drink a milkshake. You suck on the straw (vacuum) to pull the drink into your mouth. If you were to blow into the straw, it would push (boost/Pressure) the milkshake up and out of the cup.


tl;dr... do a boost leak check.


P.s. I have no clue what you said about the spark plug. Reading that part was painful.

 

[bryanwheat]

my first plug gap is gone, the rubber from running it when i 1st installed the turbo.it came right out pullin the spark plug wire.and i though boost leak test consist of vacuum check.

A boost leak can happen from the turbo to the cylinder head/manifold gasket. A vacuum leak would happen between the throttle body and Intake gasket. You can have a boost leak and no vacuum leak. You will never know until you test for one. This is something that should be done frequently because of how easy it is to get a boost leak and how it effects the car.

 

[bloodlinebkx]

A boost leak check is when you pressurize the system (turbo->IC->motor) to verify that everything is sealed and doesn't blow apart under pressure.

Think of boost/pressure as the turbo PUSHING air, it pushes on everything, the pipes, lines, couplings, gaskets...

Vacuum is the motor trying to PULL more air in. The throttle body doesnt allow much air to pass in at idle, so the motor is pulling on everything between the throttle plate and the cylinder.

Think about when you drink a milkshake. You suck on the straw (vacuum) to pull the drink into your mouth. If you were to blow into the straw, it would push (boost/Pressure) the milkshake up and out of the cup.


tl;dr... do a boost leak check.


P.s. I have no clue what you said about the spark plug. Reading that part was painful.

yea sorry about that, the valve cover gasket is gone esp spark plug number one.and im waiting on that valve cover gasket and the exhaust gasket.after fixing them i will do a boost test.

 

[bryanwheat]

yea sorry about that, the valve cover gasket is gone esp spark plug number one.and im waiting on that valve cover gasket and the exhaust gasket.after fixing them i will do a boost test.

Hopefully you aren't driving this thing like this.

 

[bloodlinebkx]

Hopefully you aren't driving this thing like this.

nope off the road and i have an f350

 

[bryanwheat]

nope off the road and i have an f350

That is good to hear. I would just take your time and get the gaskets replaced, buy some new plugs and wires, fix boost leaks and do other maintenance to the car before driving it.