No boost or power?

[chrisd000111]

My dads car is a 97 gtp, well his car has been running with no boost for a while now. The first time this happened the idler pulley locked up and shredded the belt, but fixed it and it was fine for a while. This time its not making any boost and cant figure out what it is. I checked the supercharger and the coupler is pretty shot so ill need to replace that. Just cant figure out why it isnt making any power. The boost bypass seems to be working when reving the motor you can see it open up and hear the supercharger whine a little. What else could it be. Would rather order the coupler with whatever other parts i will need. Thanks for any input guys

[Scottydoggs]

clogged cat maybe, the check engine light on?

[chrisd000111]

No check engine light

[Scottydoggs]

you can pull the o2 sensor and see if it runs better, (yes nasty exhaust leak but it lets it out if the cats clogged) or put a pressure tester in the exhaust to see if the cat is bad.

[chrisd000111]

That would cause no boost, the car runs fine. it just does not have the power like it used to. Every once in a while if you floor it the factory boost gauge will show one bar but thats it.
With the boost bypass valve, that should be down at idle and lift up when you rev the motor correct?

[Fivefingerdeathpunch]

What are the fuel trims like?

I'm guessing vacuum leak or something else.

Hook up a real vacuum/boost gauge to it to see what its really making.

[addzradd]

I'd check for vacuum/boost leaks, possibly a s/c gasket leak. 2nd I'd check to see if you broke the coupler on the SC, because the the pulley would spin but the rotors would not, easiest way to be totally sure of that would just be to pull it quick and give it a spin.

[moddman]

I second guess the coupler........if it is that bad just like the previous guy said it wouldnt make any boost if the impellers arent moving.

[chrisd000111]

I pulled the belt and you can feel the pulley spin and it has a ton of play on the coupler but it feels like it then locks up. and at idle you can hear it rattling so the coupler is bad but it doesnt feel to be a complete failure. I guess ill have to order a coupler and then when it comes in ill see if it did fail. But ill have to start checking for vacuum leaks and any broken hoses.

[Scottydoggs]

a worn coupler wont cause boost loss.

vac leak or cat are your best places to start unless a code pops up.

[addzradd]

Now why in the world would a clogged cat cause boost loss? If anything plugging the exhaust would make you see an increase in boost because air couldn't go anywhere.

On second thought even if it was a vacuum leak you would also notice a high idle, and a CEL for running too lean. How many lbs of vacuum are you seeing at idle?

[Scottydoggs]

clogged cat is the same thing as a potato stuffed up the tail pipe. the engine cant exhale. if it cant come out it also cant flow in either.

[addzradd]

Exactly my point, The supercharger would still stuff air in so boost would still be there, the power wouldn't however.

[Scottydoggs]

i dont think you'll see any boost with a clogged cat, as you are choking the engine out. like i said if the exhaust cant come out, nothing is getting in. you floor it and it just bogs or feels flat.

OP you can also drive your car around at night, and look under the car to see if its glowing red, you know its a clogged cat if its all cherry red.

[chrisd000111]

not sure on vacuum at idle. I'll have to get something to check that.

[addzradd]

I mean you can try but think about it if you blew a fan into a room, any had no way for the air to get out the pressure in the room would increase, hence boost. If anything the exhaust backing up into the intake would make the vacuum at idle very low.

[addzradd]

But to check it just to Harbor freight and get a vaccum gauge they are like 15 bucks and very handy to have in your tool arsenal.

[chrisd000111]

Ok ill try that out to see if the cat gets that hot, if it seems fine then ill start looking for vacuum leaks. I guess it could still also be the boost bypass valve, it seems to work when in park but maybe it cant open itself with the load of driving it

[Scottydoggs]

this aint no room. its a combustion engine, no air no fire no go.( its a big air pump), take a trash pump the town uses with a fire hose on it to pump water, if the screen clog's in the water, yes the pump still pumps but nothing comes out.

go stuff a banana or two up you tail pipes and go for a drive, tell me how it feels.

im guessing you never experienced a clogged cat before first hand.


not that this is necessarily the OP's problem, so back on track.

[addzradd]

Not the same, as a cat is downstream of the blower, that would be like having the pump pump water but having the firehose kinked, there would still be alot of pressure in the line which, since air can be compressed would be boost.