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Problems with lack of power


RonD

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13-14" of vacuum is WAY TOO LOW
 


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PetroleumJunkie412

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Thats.... Thats not good.

Any chance you can post a video to youtube of it running and link it here?
 

rusty ol ranger

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Isnt he at high elevation though? Not sure how much itd throw that off though

Wonder if they got the cam timing wrong when they rebuilt it?
 

RonD

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Yes, vacuum will show lower as you go up in elevation, this is also a symptom of why you lose power at higher elevations
But you should only lose a few inches of vacuum at 4,000ft

Fresh rebuilt 2.9l should have 160psi compression, so at least 18" of vacuum at seal level, would expect 20"
So maybe 16" at 4,000ft, 13-14" means a problem

I would test cranking vacuum, this is a direct compression test
So unplug the coil for a No Start
Then test vacuum while engine is cranking
3" is expected at sea level
You should see no lower than 1.5" at 4,000ft

If its low then test compression, just to take it off the table or discover that it is the issue, i.e. a valve timing issue
That way you won't waste time on "non-fixes"

As someone previously suggested it could be rocker arm issues, i.e. pushrod length, or ?? so intake valves are staying open a bit longer than they should so compression drops and so does vacuum and power
 
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reed b.

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Just getting back to this again as I've been full timing my remodel work while a friend is willing to help me. I guess I've been a bit of a 'weenie' in hoping that it is just some little thing I've overlooked; ie: just replace that one 'next' part and it would be running just great. I do wish I was able to do just the work on this truck; I wouldn't have to 'find the right page' each time. I am still another 3-4 days from being able to come back to this, so all I can do is apologize to all of you and then when I'm ready again to start at the beginning with a compression test. I've been jumping around in my diagnosis too much. Again, my thanks and I will be back with an update that I hope will include the solution to all of this. Thanks guys
 

reed b.

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I'm not all that great with the phones though I can build a damned good PC ! A 'hardware' guy I guess; it's the software that messes with my head. I'll take a video and see what I am able to do.
 

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kunar

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If i were a gambling man, i'd wager your cam timing is a tooth or two off. Have you been able to check compression?
 

reed b.

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A gasoline engine will lose 3% of its power for every 1,000ft of elevation
So if you are at 4,000ft you're already at a 12% loss of power, and that's minimum, I would guess 15% would be more likely, as loss % increases over 3,000ft
After warm up check exhaust for Rich smell that would indicate an issue with air/fuel mix of course, and contrary to what many think Rich is bad in this situation, less power and low MPG

Find your vacuum gauge
At 4,000ft it shouldn't be lower than 16"

MAP can be tested with a Volt/ohm meter with a Hz setting, graph here: https://www.aa1car.com/library/map_sensor_ford.gif
The 2 outside wires are 5v and ground, test those first, key on
Center wire will have the Hz frequency signal the computer sees

Check key on/engine off Hz, at sea level it should be 159 Hz, at 5,000ft elevation 144 Hz, so 4,000ft should be 147 Hz
The computer gets this with key on to adjust for elevation
 

reed b.

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RonD-- Just put the leads to the two outside wires of the MAP sensor and got a bit over 5 v and a hz reading of 146.4 . A compression test is next as soon as things cool down around here; 95 here today! I will now be working only on the two trucks for a few days (or hopefully fewer than that!). Thanks for the information on testing the MAP.
 

RonD

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146Hz is with engine off?
So local barometric pressure at your elevation

Did you get a reading with engine idling?
 

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I had a problem like develop suddenly. Engine felt like it had 40 HP.
It turned out to be broken gasket (old and brittle) between the lower and upper intake. I doubt that the same gasket is your problem with a new rebuild but it may be vacuum leak.
 

reed b.

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146Hz is with engine off?
So local barometric pressure at your elevation

Did you get a reading with engine idling?
 


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