Sucking through exhaust?
Elder User
Joined: Jun 2006
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The only thing I disagree with on that site is that 14" is acceptable vacuum. NOT ON THE 5.0!!! At 16, mine ran like crap. Turned out to be a shot plenum gasket in my case. On the 5.0, you want as close to 20 as you can get at idle with the IAC disconnected, spout pulled for base timing and idle.
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Postmaster
Joined: Jun 2007
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From: Sweetwater Texas
Originally Posted by Old_Paint
Huh? My test gauge was about $15 at Advance Auto, and ANY of the vacuum lines attached to the plenum can be teed if you want it in permanently. Heck, it even comes with a butt load of tees of various sizes and some rubber hose stubs so that you CAN connect it with everything else connected, and WITHOUT cutting any hoses or removing any nuts/bolts.
What the heck are you talking about O2 sensors for? On the speed density 5.0's, the O2 sensor isn't in the manifold anyway. It's in a tiny cross-over in the Y-Pipe. Since his doesn't have an ECM anyway, it won't have an O2 sensor. (Not to mention the absence of a crossover or Y-pipe on true duals) I'm not sure when Ford started using separate O2 sensors on the 5.0, but I'm relatively sure it was after Mass Air became the standard system. (Post '94)
A decent vacuum gage attached to the intake manifold will tell you more about what's going in this vintage Ford engine than ANY scanner or code reader unless the ECM has been retro'd to a newer one with fancier diagnostics than EEC-IV, or even EEC-V. In Australia, 80's and early 90's Falcons had an Economy gauge in the dash cluster. Nothing more than a vacuum gauge. Economy is a good thing to know when you head across the outback, and there isn't a fuel stop for the next 600 Km. Less throttle = more vacuum = economy. It'll tell you about vacuum/intake leaks, it'll tell you about vacuum pulses driving the MAP nuts, it'll tell you about plugged up cats/exhaust, it'll tell you about stuck valves or hosed up lifters, and it'll telll you about a restrictive air intake. And to think this is one of the tools that stealerships don't seem to have in their inventory ....
What the heck are you talking about O2 sensors for? On the speed density 5.0's, the O2 sensor isn't in the manifold anyway. It's in a tiny cross-over in the Y-Pipe. Since his doesn't have an ECM anyway, it won't have an O2 sensor. (Not to mention the absence of a crossover or Y-pipe on true duals) I'm not sure when Ford started using separate O2 sensors on the 5.0, but I'm relatively sure it was after Mass Air became the standard system. (Post '94)
A decent vacuum gage attached to the intake manifold will tell you more about what's going in this vintage Ford engine than ANY scanner or code reader unless the ECM has been retro'd to a newer one with fancier diagnostics than EEC-IV, or even EEC-V. In Australia, 80's and early 90's Falcons had an Economy gauge in the dash cluster. Nothing more than a vacuum gauge. Economy is a good thing to know when you head across the outback, and there isn't a fuel stop for the next 600 Km. Less throttle = more vacuum = economy. It'll tell you about vacuum/intake leaks, it'll tell you about vacuum pulses driving the MAP nuts, it'll tell you about plugged up cats/exhaust, it'll tell you about stuck valves or hosed up lifters, and it'll telll you about a restrictive air intake. And to think this is one of the tools that stealerships don't seem to have in their inventory ....
Thanks for telling me about the 15 dollar vacuum tester though, I called the local Autozone and asked for a price for a vacuum tester and they told me $50 bucks. Hmm, kid must have misunderstood me what I wanted.
Post Fiend
Joined: Nov 2001
Posts: 14,947
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From: Topsfield, MA
There is a haynes manual that gives very specific vacuum information. It was either in the 87-96 manual or the ford engine repair manual.
How to test it...what it should be...what tests you can do and how to do them...etc...
How to test it...what it should be...what tests you can do and how to do them...etc...
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