vacuum leak at pre-heater diaphram line
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Record Breaker
Joined: Mar 2010
Posts: 1,017
Likes: 3
From: Pittsburgh, PA
vacuum leak at pre-heater diaphram line
I have an aftermarket air filter on my truck, and I'm not running an intake preheater diaphram, as I was mostly certain its only purpose was to open and close the duct to the intake pre-heater tube.
There is one thing I am slightly confused on. In my chiltons manual, it says there is a air temperature sensor in the air cleaner, and on rockauto.com, it lists one as being in the throttle body. My truck has the one in the throttle body. I recall having only vacuum lines going to the air cleaner, with no wires at all, and therefore nothing that I would imagine could send a signal to the computer.
Without the factory intake, I have two options: A - let the vacuum line going from the TBI to the pre-heater diaphram suck in air. B - block it off.
If I choose option A, my truck misfires slightly. If I choose option B, idle is slightly slower, and when I rev the truck up and let off the gas in park/neutral, it backfires, and shoots blue and black smoke (rich + bad valve guides?) out the tailpipe.
Should I block or open the vacuum line? My thought is that it should be blocked, and the smoke and backfiring are due to an unrelated rich condition.
There is one thing I am slightly confused on. In my chiltons manual, it says there is a air temperature sensor in the air cleaner, and on rockauto.com, it lists one as being in the throttle body. My truck has the one in the throttle body. I recall having only vacuum lines going to the air cleaner, with no wires at all, and therefore nothing that I would imagine could send a signal to the computer.
Without the factory intake, I have two options: A - let the vacuum line going from the TBI to the pre-heater diaphram suck in air. B - block it off.
If I choose option A, my truck misfires slightly. If I choose option B, idle is slightly slower, and when I rev the truck up and let off the gas in park/neutral, it backfires, and shoots blue and black smoke (rich + bad valve guides?) out the tailpipe.
Should I block or open the vacuum line? My thought is that it should be blocked, and the smoke and backfiring are due to an unrelated rich condition.
Thread Starter
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Record Breaker
Joined: Mar 2010
Posts: 1,017
Likes: 3
From: Pittsburgh, PA
I think the blue is from my valve guides being worn, like having blue smoke on startup. I don't know about the timing. Its advanced a little, like to the point where I can use 87 octane for just running around, but need 89 for towing and hauling, so I can't imagine it can be too far off, though I've been proven wrong before, probably more times than I'd like to admit.
Legend
Joined: Jun 2009
Posts: 8,025
Likes: 72
From: orangeville ontario
these engines can be strange. i let my 81 sit for about 3 month but i would go start it up and move it about once a week and now that i got it insured and driving it again it seems to be smoking a lot more when i start it up than it use to. the only time it use to smoke this bad was when i first got it but who knows how long it had sat before i bought it.