Vacuum line capped off. WHY?
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New User
Joined: Apr 2007
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Vacuum line capped off. WHY?
Hello everyone. I'm new here and this is my first post. I just got a 1990 F150 4x4 with I6 engine and E4od trans. This is actually the first Ford I have ever owned.
There are two small "plugs" in the valve cover near the rear of the engine above the last two spark plugs. I am referring to the forward one, closer to the front of the engine. It may be the Thermal Air Bypass (TAB) but I am not sure.
I was changing plug wires and looking around and found
a green vacuum line coming out of the bottom of this plug , the other end is not connected to anything, and has been capped off with a red plastic cap. I removed the cap with the engine running and there is vaacum there.
Is this line supposed to be capped off or did the previous owner do it. I didn't see anyplace to connect it to, except possibly to the top of the very same plug which had a male connector exposed. But then I found a hard black plastic cap about the size of quarter laying just underneath in the engine bay and it seems the right fit to cap off the male connector so I did that.
What is this line for, should it be capped off or where does it get connected to? Thanks.
There are two small "plugs" in the valve cover near the rear of the engine above the last two spark plugs. I am referring to the forward one, closer to the front of the engine. It may be the Thermal Air Bypass (TAB) but I am not sure.
I was changing plug wires and looking around and found
a green vacuum line coming out of the bottom of this plug , the other end is not connected to anything, and has been capped off with a red plastic cap. I removed the cap with the engine running and there is vaacum there.
Is this line supposed to be capped off or did the previous owner do it. I didn't see anyplace to connect it to, except possibly to the top of the very same plug which had a male connector exposed. But then I found a hard black plastic cap about the size of quarter laying just underneath in the engine bay and it seems the right fit to cap off the male connector so I did that.
What is this line for, should it be capped off or where does it get connected to? Thanks.
Thread Starter
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New User
Joined: Apr 2007
Posts: 16
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Hey Thanks!
I reattached the vacuum hose to the EGR. It was obvious it should go there (i guess if you know what to look for).
This seems to have cleared up the stalling issue I had. When idling/coasting to a stop and and then braking it would almost shut off and on rare occasions it would stall. I guess the PO thought this might be a fix of some sort. The egr and the IAC (that is the IAC bolted to the top of the intake right by the throttle cable, right?) are both clean and shiny - must have been replaced very recently, lucky for me. Maybe he forgot to attach the vacuum hose.
I only got to test drive about 5 mi. since I dont have a tag yet, bot so far so good.
Thanks again.
I reattached the vacuum hose to the EGR. It was obvious it should go there (i guess if you know what to look for).
This seems to have cleared up the stalling issue I had. When idling/coasting to a stop and and then braking it would almost shut off and on rare occasions it would stall. I guess the PO thought this might be a fix of some sort. The egr and the IAC (that is the IAC bolted to the top of the intake right by the throttle cable, right?) are both clean and shiny - must have been replaced very recently, lucky for me. Maybe he forgot to attach the vacuum hose.
I only got to test drive about 5 mi. since I dont have a tag yet, bot so far so good.
Thanks again.
