Vacuum Issues

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Apr 23, 2011 | 10:15 PM

wesbrand

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Vacuum Issues

Hi, i am new to this site and to my 1987 F150. It is a I6 300 4.9L. I am trying to find a vacuum diagram for the truck. the factory sticker is torn right down the middle of the diagram. The issue i'm having is it's failing emmissions for high hydrocarbons. it's idling really rough and sometime stalls out while at idle. When you remove the vacuum line from the intake manifold that goes to the fuel pressure regulator valve it idles up and does ok. as soon as you reconnect it, back to rough. i have replaced the fuel pressure reg. valve, the PCV valve and hose to air box, the EGR and it has a new fuel pump. have added fuel injector cleaner and have cleaned the IAC and throttle body. no luck. it's almost like it's not getting enough air at idle and when you remove the vacuum hose from the top of the intake manifold it gets enough to run right?? any ideas?

Apr 23, 2011 | 10:53 PM

big-ugly

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Well I can't help you with the diagram, but welcome to FTE! These 4.9l's have a tendancy to develope vacuum leaks. Hopefully someone else will chime in and give you some advice.

Apr 24, 2011 | 07:08 AM

Lazy K

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https://www.ford-trucks.com/forums/9...am-needed.html Click on this link and follow the instructions by rla to get a vacuum diagram.

Apr 24, 2011 | 08:13 PM

wesbrand

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thanks

thanks for the welcome and the help everyone. i actually saw that thread the other day and checked out that website but it only goes as early as 1988. thanks for the info again everyone.