I have a question about the decelleration valve. Although this topic has come up a few times as part of various " rat's nest" discussions, I'm still unsure about the effects of removing it. I recently had a cat replacement pipe installed on my 83 GS. Within about a month after that, the "decelleration" ( or "shutter") valve went bad. I only know this because my mechanic told me that was the reason for the low moaning sound on decelleration. He recommended that the valve be removed and the associated vacuum port be capped instead of spending time and money to remove carb to fix it. I don't have the car back yet, but he says it idles much better now. He also says that the only effect I may notice is that the car may not slow quite as quickly when I ease up on accelerator.

Any comments on this? BTW, if it makes any difference in your response, I left the air pump in tact and ported outflow to cat replacement pipe so that I wouldn't have to deal with all the vacuum caps as recommended by some when cat is replaced.

Will disabling this valve have any adverse effects ( short term or long term) on the performance of the car?

Thanks for any input .

Bayou7

 

most people I have heard from on this say to just cap the line and forget about it

thats what I did , but I no longer have the pump either

 

Okay. The valve in question is activated on cruising and deceleration. It is a butterfly valve similar to a choke, and it leans out the fuel gas mixture to keep the rotary from backfiring. It has a diaphragm that tends to go bad on its actuator. Capping off the vacuum lines and making sure the valve is in the open position would be the easiest fix. The best fix would be to remove the valve from the intake manifolds airflow and plug up the holes with epoxy or JB quick. The result of not running the valve will be small backfiring on deceleration.

Good luck,

 

the hose from the valve to the air cleaner,,plug that end
(air cleaner)

 

it will foul the back plugs out quicker than the front beacue the back rotor is running rich

 

Bayou7