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7.3 low boost and drop in mpg

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Old 04-20-2012, 08:36 PM
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7.3 low boost and drop in mpg

Ive got a 01 7.3 4x4 with 222k on it. Recently my mpg has dropped from a average of 14-15 to maybe 9-10. I noticed that crusing speed (50-55 mph) that my boost gauge is barely reading anything. I went through today and checked all the boots and retightened all the clamps on my pipes. Went for a drive and stayed around 2-3lbs @50. That seems pretty low to me still.
I can turn my programmer up and floor it and it will jump up to 26-27 lbs, but qucikly drop once i let off.

Any ideas what to do next?
 
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Old 04-21-2012, 06:58 AM
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Make you a boost leak detector. Go to the hardware store and buy you a 3" PVC end cap, and if you don't already have them, a threaded fitting that you can snap an air hose into and a tap so you can screw the fitting in.

The OD of the end cap is 4", so undo the end of your air intake line and stick the end cap in the hose and clamp it in place using the factory hose clamp. Then hook up an air compressor with the pressure regulated down to 5 - 10 psi. Spray all your connections or any suspect leak locations with soapy water and look for your boost leak.
 
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Old 04-21-2012, 08:35 AM
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2-3 # boost at 50 is about right. The boost falling off when you get out of it is normal. The amount of boost you get at WOT is great.

I don't see a problem with your boost.
 
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Old 04-21-2012, 08:49 AM
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That MPG completely sucks. I wouldn't rule out exhaust leaks on your manifolds, ups, and collector - I'd go on soot safari.

The last link in my sig might help.
 
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Old 04-21-2012, 11:50 PM
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Moved to the 1999 - 2003 7.3L Power Stroke Diesel forum.
 
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Old 04-22-2012, 07:56 PM
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Originally Posted by miller_feed View Post
2-3 # boost at 50 is about right. The boost falling off when you get out of it is normal. The amount of boost you get at WOT is great.

I don't see a problem with your boost.
It was at 0 before I tightened everything. It just still seemed low to me, but if its normal than i guess its all good.
 
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Old 04-23-2012, 08:11 AM
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Originally Posted by TheTinian View Post
It was at 0 before I tightened everything. It just still seemed low to me, but if its normal than i guess its all good.
I blew a boot off before and drove 50 mph for 3 miles to get back to my shop with the boot completely off. So 2-3 # boost is good for 50 mph.
 
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