air injection check valve (1 Viewer)

Joined
Jul 4, 2007
Messages
30
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Keene, NH
The air check valve on the exhaust manifold pipe (NOT the check valve at the air rail) has rotted in half, and I don't think I can remove the remaining piece. I'm thinking of cutting off and capping the small (1"?) exhaust pipe extension that the check valve mounts to (rather than get a new exhaust manifold pipe).

I would then leave the air pump inlet pipe open to atmosphere (I still have all emission control equipment). The only effect I see is that air pump supply won't receive the heated exhaust air - just ambient air in the engine compartment.

I am in New Hampshire where they don't require emission testing on a vehicle this old.

Anyone see a problem with this approach?
 
Joined
Oct 19, 2013
Messages
2,366
Location
NY
That check valve (when working properly) allows gas to flow in one direction.

The check valve you are referring to (the one on the skinny exhaust pipe that mates into the exhaust down pipe) prevents the flow of exhaust back up into the ABV/ASV assembly, but allows air from the air pump (when the ABV/ASV assembly is in 'air bypass' mod) to flow past that check valve and down the skinny pipe, into the exhaust downpipe and out through the cat/muffler system.

When the check valve is no longer working properly, it allows exhaust to flow back up into the ABV/ASV assembly.

To answer your question, cutting and plugging that skinny pipe will have no affect on the functioning of the ABV/ASV system...it will just mean that the air (when the ABV/ASV is in bypass mode) will not flow down and out through the exhaust, but rather be pumped into the engine bay. This might have an affect on the performance of the CAT, but I'm not sure to what extent and how you could measure it. Maybe @Pin_Head could answer that question.

I recently replaced both of those check valves (they are available from Advance Auto, although pricey). To replace the one on the exhaust pipe, I had to remove the exhaust downpipe (if you do this, get a new OEM doughnut gasket for the exhaust manifold/down pipe fitting). If you are going to remove the downpipe to cut and plug that pipe, might be just as good to go ahead and replace that check valve with a good one...?
 
Joined
Jul 4, 2007
Messages
30
Location
Keene, NH
That check valve (when working properly) allows gas to flow in one direction.

The check valve you are referring to (the one on the skinny exhaust pipe that mates into the exhaust down pipe) prevents the flow of exhaust back up into the ABV/ASV assembly, but allows air from the air pump (when the ABV/ASV assembly is in 'air bypass' mod) to flow past that check valve and down the skinny pipe, into the exhaust downpipe and out through the cat/muffler system.

When the check valve is no longer working properly, it allows exhaust to flow back up into the ABV/ASV assembly.

To answer your question, cutting and plugging that skinny pipe will have no affect on the functioning of the ABV/ASV system...it will just mean that the air (when the ABV/ASV is in bypass mode) will not flow down and out through the exhaust, but rather be pumped into the engine bay. This might have an affect on the performance of the CAT, but I'm not sure to what extent and how you could measure it. Maybe @Pin_Head could answer that question.

I recently replaced both of those check valves (they are available from Advance Auto, although pricey). To replace the one on the exhaust pipe, I had to remove the exhaust downpipe (if you do this, get a new OEM doughnut gasket for the exhaust manifold/down pipe fitting). If you are going to remove the downpipe to cut and plug that pipe, might be just as good to go ahead and replace that check valve with a good one...?
 
Joined
Jul 4, 2007
Messages
30
Location
Keene, NH
Ahhh. Thank you Slow Left! I didn't understand the flow of air from the air pump. Removing the exhaust downpipe and replacing the check valve is the right thing to do......and I usually end up doing that...but have to consider the short cut first!
 
Joined
Oct 19, 2013
Messages
2,366
Location
NY
Ahhh. Thank you Slow Left! I didn't understand the flow of air from the air pump. Removing the exhaust downpipe and replacing the check valve is the right thing to do......and I usually end up doing that...but have to consider the short cut first!

Well, it seems just as much hassle as cutting/plugging the pipe...especially if you have to remove the down pipe to cut/plug anyways...

Just note, save and reuse that rubber hose that goes between the check valve and the metal outlet pipe on the ABV/ASV. Don't cut that hose!!! They are no longer available through Toyota and there is a bend to it that is hard to replicate (a straight hose will kink). You can detach it from the ABV/ASV pipe and it will come out with the exhaust down pipe...and then remove the hose/check valve with the down pipe off the vehicle. You don't have to jack up the vehicle to slide the down pipe out from underneath it, it slides forwards over the axel housing and out the front...
Get new OEM hardware (bolts/nuts/washers/ for the cat/down pipe connection (and use plenty of antisieze on those threads). I would also get new nuts for the downpipe/exhaust manifold studs (and donut gasket as I mentioned above).

Also, if you want to go the whole desmog route, here are instructions on how to desmog. See Jim C. ( @FJ40Jim) for hardware (idler pully, plates, gaskets and plugs):

http://www.tlcperformance.com/
 

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Joined
Sep 22, 2008
Messages
370
Location
NYC, mostly
Since you're disabling the air injection, I'd seriously consider doing a full desmog. Otherwise, your smog pump, which is now just taking up space an a complicated idler pulley, will die on you at a terribly inopportune moment.

Post-desmog, my cat is actually running hotter now that I've removed all the Non-functional smog crap. This tells me that it was just sitting there looking pretty and making funny noises, rather than doing anything worthwhile. You might also be in the same boat.
 

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