popping noise @ WOT

[GNVYUS 1]

Rockauto sells a Denso Stainless 02 sensor which is around $17, Denso also makes the best intank fuel pump for us the 280.

Just to confirm, pressure is 1:1 at WOT when you say it's good?

Do you have a wideband reading or a MV narrowband reading while WOT?

 

[buickrob]

You ohmed the coil pack but did you throw new wires on it? They are 21 years old and I'm sure they are not insulated like they should be anymore.

 

[6-Banger]

Yes the fuel pressure increases 1psi per 1psi boost. original 02 sensor, I'm using a scanmaster, the car only has 16,000 miles. Original plug wires.

 

[buickrob]

Original plug wires.

I really think you need to change those wires. Anybody else agree with that?

 

[Phoneguy]

headgasket!!!!. exhaust is escaping between the head and block. check out the other easy ways to eliminate first but it sure sounds like a headgasket especially if this just started

+1 , sounds like you are lifting a head at high boost. Ask me how I know:biggrin:

Bryan

 

[6-Banger]

You can lift a head at high boost then it will seal itself back up? I've never heard of that before. Compression good, doesn't run hot, no drivability issues until under WOT.

 

[Phoneguy]

Won't always show up on a compression test. Leak down would be better. I was running Cometic gaskets with Aluminum GN1's, lifted both heads at 22#s and up.

Bryan

 

[gbsean]

how much gas is in the tank when this happens.....

 

[mikestertwo]

You can lift a head at high boost then it will seal itself back up? I've never heard of that before. Compression good, doesn't run hot, no drivability issues until under WOT.

I had a friend with the same issue. No drivability problems. We checked the compression. All cylinders were from 145-150 lbs. Took it out for a W.O.T. run. It blew the left head gasket (#3 cylinder) into the lifter valley

 

[cabech984]

I really think you need to change those wires. Anybody else agree with that?

I know I wouldnt be putting 20+lbs of boost on the original plug wires, especially since the car has sat most of its life.

You can lift a head at high boost then it will seal itself back up? I've never heard of that before. Compression good, doesn't run hot, no drivability issues until under WOT.

I was lifting a head and the only way I could tell was by running excessive boost. I'd turn down the boost to minimum setting and see whats up.

 

[ericmccann]

Check the Turbo breather inlet port

I had a friend with the same issue. No drivability problems. We checked the compression. All cylinders were from 145-150 lbs. Took it out for a W.O.T. run. It blew the left head gasket (#3 cylinder) into the lifter valley

I had the EXACT same thing happen to my 1987 GN and found that the definitive root cause of the problem was that the breather port on the backside of the turbo which normally connects via an "S" shaped hose to the front of the passenger side valve cover was completely disconnected from the Turbo, thus allowing in massive amounts of *unmetered* air into the intake air stream, especially under boost. Under boost is the only time I had the issue as well.

Capping off that port on the intake (back) side of the turbo intake fixed the problem, after blowing the head gasket for center cylinder on the drivers side into the lifter valley before finding the problem. I only found the problem while tearing down the top end of the motor and once I saw that open port on the Turbo, it all made sense.

I did replace the coil, ignition module, IAT sensor, plugs, plug wires and O2 sensor prior to finding the open port on the turbo and the problem persisted until finding that open port on the turbo and capping it off. After I capped it off, the problem just simply went away completely.

Hope this helps.

Best,

Eric McCann

 

[6-Banger]

I have raced the car in this condition about 8 1/4 mile passes and plenty hard on the street(I assumed it was just an exhaust leak of sorts). I have already done the #3 fire ring into the valley trick 1 1/2 years ago. It's a TE-44 with no inlet bell, therefore I don't have the S shaped hose to the passenger breather. I think I'm going to check the torque settings on my headstuds.

 

[TurboBuRick]

Did you check the cam?

 

[V8killR4U]

Won't always show up on a compression test. Leak down would be better. I was running Cometic gaskets with Aluminum GN1's, lifted both heads at 22#s and up.

Bryan

How did you fix the lifting head problem? Did you simply retorque the heads. Im experiencing similar issues. (Would this cause any lean conditions in the car when at WOT)