Failed Diverter Valve

surfdog4 · 05:44 AM

My diverter/blow off valve has become yet another vacuum leak. Currently it is sending air only to the air filter..since the thing seems to cost $250-$350, i haven't figured out exactly how to remove it, and i do not have to pass emissions testing I was wondering if i can just leave it there. Right now i just plugged the vacuum line. (this is an '81 US car)

The cat is still there but from what i gathered it only gets air at times of high vacuum so seems like it's not doing much.

Thoughts?

ROG100 · 09-11-2008, 07:05 AM

Plug the vac line and cut the air pump belt

Danglerb · 09-11-2008, 08:31 AM

Wild guess, but isn't the air to help the cats burn off as they cycle between rich and lean? If so without the air the cats may not burn off as well and idling might cause some level of build up, maybe reducing cat life and/or generating a lot of heat when it burns off during cruise?

Yours probably hasn't worked in a long time, so I agree with Roger, or just pull it all off when convenient and get rid of the weight. Any modern cat that you put on isn't going to need air anyway.

ROG100 · 09-11-2008, 08:40 AM

My thoughts are the cat is probably clogged anyway. Get rid of it and fit a Y pipe and get some more ponies working for you.

surfdog4 · 09-11-2008, 11:09 AM

well since it's all plumbed in there now and pumping away into the air filter I'm going to leave that for now and move on to my other problems...

One thing i did think of was since i was redoing all those breather hoses anyway i could plumb the vapor venting from the fuel tank into the cat...maybe that would create some bang! Like a jet afterburner!

..or at least the BatMobile!

Danglerb · 09-11-2008, 12:00 PM

Having your cats glow red hot isn't nearly as much fun as it sounds.

surfdog4 · 12:38 PM

oh c'mon what could possibly be the problem with a glowing red cat?

now for my "wandering idle" issue: well today at lunch i went out and bought some length of 3/4" and 5/8" hose and some caps..I'm going to bring out the lines that the vacuum limiter attach to so i can experiment with just having them capped or installing a new limiter..but not having to tear out the whole mess a third time.

The best info i could find seems to indicate that on a 5-speed you can cap the lines if you also disconnect the idle switch..but with these cars who knows! so if i bring the lines out where i can reach them then either way it's easier to work with

hate to say this, but all this does make me appreciate my hondas with tons of miles that just keep running and running..of course i got myself into this by buying a "Project car"...so enough whining..back to the wrenches!!!!

Danglerb · 09-11-2008, 01:36 PM

Without the vacuum limiter if you downshift and let off the gas the vacuum gets so high that the mixture won't ignite, until it gets to something hot, BOOM. Used to do that when I was a kid, downshift, and turn the ignition off and back on. Nice boom.

surfdog4 · 04:34 PM

first i had heard of that..i had heard that if you leave the idle switch on the rpms will drop very low...apparently several people deleted it from the autos with no issues (maybe the transmission itself bleeds the vacuum down?)..and it was a factory delete on '83 up

well i have to get in there anyway to see if that limiter is causing my up and down idle..i know it's not leaking vacuum because i checked it but someone said they can get "weak"..meaning i guess they partially open and cause air leak between the upper and lower throttle

Danglerb · 09-11-2008, 07:07 PM

Not exactly deleted, replaced with the idle stabilizer.