Thanks for the help. Replaced the cannister purge valve and the "putt-putt" noise quit. Will recheck the codes when I get a chance. Total cost: about 15 minutes and 24 bucks(express mail postage on the valve).
--
We have met the enemy and they is us. [Pogo] S70 cop car : Rough Rider tires& suspension, Walmart fog lights, eBay speakers, ambiance by Pall Mall, trim by Le Duc d'Tape, 8-channel THD by OEM amps

Here it is. This was originaly posted on 9/26/03 on the other board.

It has been two weeks since I cleared the CEL. I had P0455 code, which is a major EVAP leak detected in the gas tank.
This is what I did.
I got under the car and checked all the hoses and connections to the canister and to the fuel tank. I checked for visible signs of breaks, looseness, etc.
Everything checked OK.
I removed the purge valve located on the radiator fan shroud. I didn't notice anything unusual. This valve has been routinely replaced to correct a common problem with the valve sticking and/or not closing properly, hence, purging the canister when it is not suppossed to.
I applied 12 volts to make sure it was operational. You will hear clicking. If you can apply very low pressure air, you will hear and feel the valve opening.
I sprayed carburator cleaner and using the lowest seting in my compressor (about 5 PSI) I blew the carburator cleaner and air through the valve in both directions. I pressurized the valve and then activated it to run the mixture through the valve.

***THIS IS VERY DANGEROUS, YOU ARE MIXING AIR, FLAMABLE LIQUID AND USING ELECTRICITY THAT CAN GENERATE SPARKS AND CREATE A FIRE****

I discharged the mixture into a shop rag to avoid a flamable mixture in the air. Also, the power to the valve was connected away from the valve and not at the valve itself, so the spark was not a the area where the carburator cleaner was.

I did the procedure two times with some soaking in between. I tested with air only to remove all the carburator cleaner.
I sprayed some WD40 for lubrication and applied more air and activated it again.

As an added measure, I cleaned the seat of the gas tank filler neck with 320 sandpaper so the gas cap has a good seal. If you do this, make sure you stuff a rag in the filler tube so the debries don't go into the gas tank.

Re-installed on the wagon, cleared the code and I have not seen the light in two weeks now. In the past ,the light will re-appear after 1 or 2 days after clearing the code.

Saved about $140.00 for the part plus the labor.

Make sure it was not generated by a loose gas cap or a poor seal of the filler neck and/or gas cap gasket.
Most of the time this code is an indication of a defective purge solenoid (on top of the radiator).
I was able to remove the solenoid and clean it with carburator cleaner and low pressure compressed air.
The code never returned.
If I can find the process I posted on Volvospeed I will post it here.