SoSoFresh_SS

HOW IMPORTANT IS A DECELERATION VALVE? DO I ABSOLUTELY NEED IT TO PASS EMISSIONS AND RUN BETTER??? I'M HAVING TROUBLE FINDING THIS PART. NOBODY SEEMS TO CARRY IT. A MECHANIC TOLD ME THAT REPLACING THE DECEL VALVE IS MORE IMPORTANT THAN MY BAD CHOKE PULLOFF AND EGR SOLENOID. IF I BUY A REMAN VARAJET FOR MY 84 V6 BIRD WILL IT HAVE A DECEL VALVE ALREADY ON IT???

Sonix

iTrader: (1)

you break your capslock button man?

I've never even heard of a decel valve... Is this like buying a new powerband, or muffler bearings, or something real?

SoSoFresh_SS

Was that supposed to help me man? If so, thanks!!! I took the caps off for you. ENJOY!!!

Saabster

iTrader: (2)

It means we've never heard of a deceleration valve. What is it? Where is it? What's your car doing as a result of it being broken?

Saber

iTrader: (2)

Yea, i have never heard of such a thing, your not talking about an EGR valve or a PCV valve are you? those are the only valves i know of that deal with emissions and might cause you to fail.....

*Edit*

A quick google search turned this up

A deceleration valve for use in a vehicle emission controls system is responsive to increased engine manifold vacuum (thereby indicating a vehicle deceleration) to vent the vehicle air cleaner through the intake manifold for a controlled period of time to eliminate exhaust backfiring and to reduce hydrocarbon emissions. The valve mechanism includes a diaphragm assembly comprising an annular flexible member having an outer periphery clamped to the valve housing and an inner periphery clamped between a pair of diaphragm plates. One of the diaphragm plates has an axially projecting portion which extends through the opening in the flexible member. The other diaphragm plate has a plurality of axially extending, resilient legs which circumscribe the axially projecting portion of the first diaphragm plate and are yieldable in a radial direction so that they are able to snap into a groove on the axially projecting portion when the valve is assembled. The axially projecting portion also receives a barbed pin which connects the diaphragm assembly with the valve. A check valve is carried in the diaphragm assembly, to control communication across the assembly.

SoSoFresh_SS

Thanks dude,

So do you believe if I change the EGR and Choke Pull-Off, Its a chance that I might pass emissions because, I passed my hydrocarbon emissions reading with a 134.5 out of 157.0(which was the limit). I think I broke it off a while back but it was rusted badly anyway. If most of you guys have never heard of it I dont think its that important.

Apeiron

These cars never came with a deceleration valve.

SoSoFresh_SS

Are you sure??? I wouldn't know, this is just what the mechanic told me.

The car is a 1984 Firebird 2.8 v6 2bbl

Sonix

iTrader: (1)

Thanks Ape. That's kinda what I figured, and was hoping someone would know.
So in truth, your mechanic is trying to sell you muffler bearings.

Saber

iTrader: (2)

I have never heard of a deceleration valve, i just googled it in hopes someone would know what exactly it is, I dont know anything about emissions testing, and seeing as you have an 84, its not like your emissions equipment is super sophisticated, especially if you have a carb. My guess would be to tell you to try changing your PCV, or at least inspect it. Its a 2$ part anyways so it cant hurt, or take you car to someone who knows what they are doing because frankly, he should have been able to tell you why it didnt pass.

Air_Adam

Sounds like maybe whats otherwise called a 'dashpot'...

Its a little damper for the throttle lever on automatic cars with carbs, that lets the throttle lever down slowly, because if you stab the throttle with an auto (in gear) and then let off right away, it can sometimes stall because the load doesn't go away. This little gadget just slows down the 'snapping shut' of the throttle to prevent it potentially stalling on you.

I don't know if these cars ever had one, because mine was a 5-spd, but I know they exist. That may be what he's referring to.

Apeiron

A dashpot is a little different, it delays the throttle closing instead of bypassing the throttle body.

Damon

Not sure if your 84 V6 had one of those deceleration valves but here's what it does if you got one.....

It momentarily interrupts the flow from the air pump (smog pump) into the exhaust manifolds and/or cat and diverts that flow through a small muffler/diffuser to the outside air. It responds to a strong peak in intake maniflold (via a vacuum line) like when you snap the throttle shut from elevated RPM. After a few seconds it opens again and airflow from the pump is again routed back into the exhaust system like normal. It does this to prevent backfiring through the exhaust during this 'over-run' situation. It's default position is CLOSED (pumping air into the exhaust).

Later FI engines like the TBI and TPI systems still have them but they are more sophisticated and are under ECM control- they are called 'diverter valves' which can direct smog pump flow to the manifolds OR the cat OR to the outisde air.

I had one on an old 1980 Z-28 I owned and I was scratching my head over what that damned thing was there for! The assembly is usually bolted on or very near the smog pump itself.

Do you NEED it? Well, if it's totally gone, then your smog pump won't be pumping air into the exhaust like it should under most normal conditions and it could definitely increase your tailpipe emissions.

Camaroboi

I know what you are talking about, I went to napa and they could only find it MANUALLY. In a sense of what it was found as was called a "vacuum air valve". It appeared to be reverse setup. I'm gonna get it and let you know if it works or not. Also, I am beginning to question GM, because EVERY time I call them they say "discontinued part".

Keith Maloy

A deceleration valve is a real part. It was only used on the v6 manual models for evacuating built up pressure in the manifold when the throttle was let up ( closed ) during shifting. It helps to regulate the drop off in power between shifts. It is not the valve used by the A.I.R. system. It has three hose connections one vac. line and two pcv lines. It seems possible to live without. GM discontinued the part and no major suppliers seem to have it. It's been said though it helps rebalance the fuel air mix when the throttle is closed making for a cleaner burn and tries to reduce plug fouling.

mustangman

first off the deceleration valve is real you can google it or you can buy a Haynes Manual for your Firebird you can go to a salvage Yard they probably have one or they can order it