2000 GTP bogs under boost

[gtp'n]

Hey guys. I have been on this forum for a while. I do not post much but I do lurk a lot. Most of the time I am able to do a search and find the answer to my problem but this time I can not. I have a 2000 GTP the car has 117,000 on it and is completely stock. It seems to booge down when the supercharger creates boost and the power is not there. This only happens when boost is created. You can feel the car shake slightly and goes away a soon as you lay off the gas. You can tell it wants to go but just does not. The car never dies and the rpm's stay steady. This is what I have done to narrow it down.

I put a new tank of gas in the car and also added a can of iso heet. Thinking I had some condinsation in the tank
I took the car to advanced and ran a scan. It came up with no codes.
I changed the airfilter with an extra one I had. I could not see any thing that could be blocking the air.
I disconnected the MAF sensor test drove the car with no change.
I then pulled off the SC belt and took it for a drive. The problem was gone. Obviously I did not have the power as before but no suttering at all. I then cleaned the belt(gaterback) and reinstalled it. The problem can back.

The problem first started the other night. I have been driving on it the last few days. The problem seems to be better the when it first happened but it is still there.

I did not see any lines diconnected but could I have a vaccum leak. Maybe a bad plug or wire?

Thanks for the help in advance

[CrazyHorst]

I'd have to ask if you've changed the fuel pump...

Fueling is proportionate to power and there aren't many diagnostics for fuel pressure...at WOT the fuel pump has to work the hardest...there's no intake vacuum to assist flow (the fuel pressure is regulated to be a constant absolute pressure differential....fancy way of saying it is regulated to a lower fuel line pressure when there is manifold vacuum)

Your GTP is in the mile and year range where this would also seem to be a good planned maintenance item IMHO.

[gtp'n]

Originally Posted by CrazyHorst

I'd have to ask if you've changed the fuel pump...

Fueling is proportionate to power and there aren't many diagnostics for fuel pressure...at WOT the fuel pump has to work the hardest...there's no intake vacuum to assist flow (the fuel pressure is regulated to be a constant absolute pressure differential....fancy way of saying it is regulated to a lower fuel line pressure when there is manifold vacuum)

Your GTP is in the mile and year range where this would also seem to be a good planned maintenance item IMHO.

It is the original fuel pump. If the fuel pump was the issue don't you think the car would act the same at WOT with or withut the supercharger hooked up. At this time I am leaning toward changing the plugs and the wires. They are original. I know ac delco wires are recommended. Any recommendations on plugs?

[CrazyHorst]

It would of course be best if you had a fuel pressure gage to hook to the Schraeder on the fuel rail for a true quantitative measurement.

Changing the plugs and wires isn't a bad idea either and requires less work. Any chafing and the spark energy can go somewhere else unintended.

I like to buy rolls of the high-temp split black conduit (from McMaster Carr) and put plug wires inside of this to prevent such chafin issues...the OEM black plastic "organizer" clips are good for about 1 use only....

Quick tip for changing the rear bank plugs is to undo the torque reaction brackets which attach by "dogbones" to the upper rad support. Use a ratcheting web-strap clamp to roll the engine forward until you now have access to the back side of the engine. Be careful as the front manifold can crunch the radiator fans if you go too far...

[BNaylor]

Interesting. Booges? You mean a bog or bogs? Or a misfire feel?

What does your boost indicator read at the DIC? Check your boost bypass valve and solenoid. Also, make sure the vacuum lines are connected properly and vacuum is proper. You should see around 18-22 in-hg with an automotive vacuum gauge at idle and about the same range of vacuum at a steady 2K rpms.

[gtp'n]

Originally Posted by BNaylor

Interesting. Booges? You mean a bog or bogs? Or a misfire feel?

What does your boost indicator read at the DIC? Check your boost bypass valve and solenoid. Also, make sure the vacuum lines are connected properly and vacuum is proper. You should see around 18-22 in-hg with an automotive vacuum gauge at idle and about the same range of vacuum at a steady 2K rpms.

It does feel like the engine is misfiring. I checked the vacuum lines and did not see anything unusal but I did not put a gauge on it. How do I check the boost bypass valve and solenoid? What do they look like?

[HotZ28]

Originally Posted by gtp'n

What do they look like?

When you rapidly increase RPM, you should see the rod on the bottom of the solenoid move.

[gtp'n]

Originally Posted by HotZ28

When you rapidly increase RPM, you should see the rod on the bottom of the solenoid move.

OK I thought that is what that was. I did move it up and down by hand to make sure it was not stuck. It seemed to move fine. If I have someone rev the engine while in park should this move? I do not recall creating boost when reving the engine.

[BNaylor]

Originally Posted by gtp'n

If I have someone rev the engine while in park should this move? I do not recall creating boost when reving the engine.

What reading do you get on the boost indicator at the DIC in aggressive street driving or heavy acceleration?

If it feels like a misfire then try the routine tune up items first. Fuel filter, plugs, wires. Does the SES/CEL light blink?

[gtp'n]

Originally Posted by BNaylor

What reading do you get on the boost indicator at the DIC in aggressive street driving or heavy acceleration?

If it feels like a misfire then try the routine tune up items first. Fuel filter, plugs, wires. Does the SES/CEL light blink?

The boost indicator works normally.When you step on the gas the gauge acts normal. The car tries to accelerate and does just not like normal.

I get no warning lights and the computer has no codes stored.

Any recommendations on plugs and wires and the best place to get them.

[BNaylor]

Originally Posted by gtp'n

Any recommendations on plugs and wires and the best place to get them.

If you are stock I would recommend using the AC Delco Premium Silicone 7mm wires or even aftermarket like the Taylor Spiro Pro 8mm wires. On spark plugs the AC Delco 41-101 Iridium which are made by NGK for GM or the NGK TR55IX Iridium. Also, Autolite copper core 606, platinum (AP606) or double platinum (APP606) work fine. The Autolite numbers match the stock heat range. Gap at .060".

[gtp'n]

It looks like the issue is now resolved. Yesterday I did plugs, wires, fuel filter and pcv valve. I then took it for a test drive and the issue has gone away. When I pulled the plugs and compared them to the new ones you could see that they were in bad shape. A couple of the points were completely gone.

Thanks to everyone that chimmed in to help me track down the problem. This is a great forum and the people on here really know the stuff.