1993 mercury grand marquis.

1993 MERCURY MARQUIS
100,000 MILES
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DOBYBEARS
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  • 3 POSTS
have taken 2 recent trips of 500 miles. When I get to around 300 miles, the car starts bogging down and will not go over 45 mph. It will snap out of it for awhile, then bog down again. While it is doing this, it uses twice as much gas as usual. When I get diagnostic reading at the parts store, all they can tell me is it's a fuel problem but cannot find specifics. Any ideas
Nov 4, 2011 at 4:46 PM
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FIXITMR
  • ✓Experienced Mechanic
  • 9,989 POSTS
so the CEL does not come on? what motor is it?
Nov 4, 2011 at 8:10 PM
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DOBYBEARS
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  • 3 POSTS
it's a v8
Nov 5, 2011 at 9:21 AM
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CADIEMAN
  • ✓Experienced Mechanic
  • 3,544 POSTS
you need to know the fuel pressure when this happens.also remove the o2 sensor to check for a pluged exhaust.
Nov 5, 2011 at 9:32 AM
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FIXITMR
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so it only does this on long trips? is it all highway (300)?
Nov 5, 2011 at 10:11 AM
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DOBYBEARS
  • MEMBER
  • 3 POSTS
Yes, it is only on long trips on the interstate. It seems to run fine in town. But after driving 300 miles non-stop when it's getting down to about 1/4 tank of gas, that's when it starts bogging down.
Nov 5, 2011 at 11:14 PM
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FIXITMR
  • ✓Experienced Mechanic
  • 9,989 POSTS
i'm thinking it could be an EGR valve issue? or fuel pump issue?
Nov 6, 2011 at 8:46 AM
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