2005 Engine troubles...missing

[ThomasJ2895]

Recently the car began to miss and will only throttle up to about 3800. The code that comes up is P0300 - random multiple cylinder misfire detected. White smoke is also coming out the tail pipe. It has about 70k mi. It is a 3.8 V6 supercharger. Any helpful thoughts would be greatly appreciated.
Thanks,
Tom

[tblake]

Hi Tom.

I would suggest to rent a vaccum guage and check engine vaccum at idle and at 2000 rpm's. Once at 2000, vacuum should stabilize. If it slowly decreases, your cat converted is bad.

Also could try a fuel pressure check to rule out the pump.

To me it sounds like the cat converter.

[ThomasJ2895]

Originally Posted by tblake

Hi Tom.

I would suggest to rent a vaccum guage and check engine vaccum at idle and at 2000 rpm's. Once at 2000, vacuum should stabilize. If it slowly decreases, your cat converted is bad.

Also could try a fuel pressure check to rule out the pump.

To me it sounds like the cat converter.

Thanks for your suggestion...I pulled the CAT last weekend (incredibly easier than on my new beetle) and had it eye-ball examined by a local shop...he seemed to think it looked fine (I pushed air through it and it flowed easily).
I bought a new fuel pump that I will replace, maybe today, picked up some new plugs and wires and will replace those today, though I have never, in many years of shade-treeing-it, found plugs and wires to make any difference...only doing it because some threads I read here pointed in that direction.
After the new plugs/wires, assuming nothing has changed, I'll put a vacuum gauge on the vacuum system and report back.

Thanks again for your help...greatly appreciated.
Tom

[grandprixgtx00]

Originally Posted by ThomasJ2895

though I have never, in many years of shade-treeing-it, found plugs and wires to make any difference

for a miss? plugs do wonders most of the time...especially with 70K on the car

edit: another thing you can do is put a can of seafoam in the gas tank after the fuel filter, plugs, and wires to clean out the injectors a little bit