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  #1  
Old 12-07-2003, 01:22 PM
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valve adjustment and now poor mpg?

Hi,
yestrday I wrote about the valve adjustment I did... seemed to go well, but some of the values were quite a bit off. Today I drove out the rest of my tank of fuel, and only got 26 mpg, not my usual 29-30. Also, I noticed from my turbo gauge that cruising at 70mph, I was at full (8psi) boost constantly, whereas I kind of remember (maybe Im wrong), that before my boost would be 5-6-7 psi at 70-75 when cruising, but go up to full when I accelerated.

Could an incorrectly done valve adjustment cause me to drop MPG a LOT, yet still have the car start great cold, and run very smoothly?
Could it cause me to in some way either require heavier throttle to keep a certain speed (which I didnt particularly notice), or require more boost (which I suppose is directly proportional to throttle position) when moving?

I just am not very confident in my work, and want to be sure that it is right, so Id appreciate info on this for reassurance or so I can get it fixed before I do damage and get really poor MPG...

Thanks

JMH
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  #2  
Old 12-07-2003, 01:30 PM
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First of all, you really need to run at least complete two tanks of fuel for any assessment of mpg.

Second, check to see if the overboost/ALDA line has become disconnected somewhere.
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Old 12-07-2003, 01:34 PM
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I keep a running tab of MPG, every tank... And always get it from the same place (flying j truckstop). But I agree, and Ill wait a tank or two to see.

JMH
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Own:
1981 240D (73K)
1982 300CD (162k)
1991 350SD (113k)
1998 Chevrolet S-10 ZR2 (62K)
2011 BMW 135i cv (14k)
2014 Honda Odyssey (6k)
2015 Honda Accord Hybrid (5k)
Had:
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1991 BMW 318i (183K)
1983 300D (228K) (wrecked by at-fault uninsured driver)
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1992 Toyota 4Runner (72k) (Rusted out)
1990 Daihatsu Rocky (??) (No parts)
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Old 12-07-2003, 06:08 PM
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I always have 7-8psi @ 65mph and 10psi+ at any higher speed.
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Old 12-07-2003, 08:50 PM
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I've always noticed a small decrease in fuel mileage when I get my first tankful of winter formulation fuel and , of course, it does not increase until summer formulation of fuel is back. I have never had as big a drop as you have described (usually I notice about 1 mile to the gallon decrease). Just a thought.
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  #6  
Old 12-08-2003, 10:37 AM
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Its been very, very windy in the Delaware/New Jersey area for the last couple of days. Your higher turbo boost is consistent with an engine that is producing more power to fight a headwind. Any chance you were driving into the wind for a significant part of your last tank?

Winter grade diesel fuels will also cause lower mileage.

Tim
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Old 12-08-2003, 04:58 PM
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Probably just winter fuel. It will be hard to tell unless you have MPG data from last winter. You may need to wait until spring to know for sure!
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  #8  
Old 12-08-2003, 05:11 PM
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last winter:27.36-30.68mpg
switched to my d1 mix part way through the winter...

jmh
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Own:
1981 240D (73K)
1982 300CD (162k)
1991 350SD (113k)
1998 Chevrolet S-10 ZR2 (62K)
2011 BMW 135i cv (14k)
2014 Honda Odyssey (6k)
2015 Honda Accord Hybrid (5k)
Had:
2008 VW Rabbit (70k)
2004 SAAB 9-3 (83k)
1991 BMW 318i (183K)
1983 300D (228K) (wrecked by at-fault uninsured driver)
1985 300D (233K) (now in FL)
1994 Acura Integra (188k) (Rusted out)
1992 Toyota 4Runner (72k) (Rusted out)
1990 Daihatsu Rocky (??) (No parts)
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