1993 Mercury Grand Marquis.

Tiny
DOBYBEARS
  • MEMBER
  • 1993 MERCURY MARQUIS
  • 100,000 MILES
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
Friday, November 4th, 2011 AT 11:46 PM

6 Replies

Tiny
FIXITMR
  • MECHANIC
  • 9,990 POSTS
So the CEL does not come on? What motor is it?
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Saturday, November 5th, 2011 AT 3:10 AM
Tiny
DOBYBEARS
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It's a v8
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Saturday, November 5th, 2011 AT 4:21 PM
Tiny
CADIEMAN
  • 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.
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Saturday, November 5th, 2011 AT 4:32 PM
Tiny
FIXITMR
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So it only does this on long trips? Is it all highway (300)?
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Saturday, November 5th, 2011 AT 5:11 PM
Tiny
DOBYBEARS
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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.
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Sunday, November 6th, 2011 AT 6:14 AM
Tiny
FIXITMR
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I'm thinking it could be an EGR valve issue? Or fuel pump issue?
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Sunday, November 6th, 2011 AT 4:46 PM

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