1999 Pontiac Grand Am poor fuel economy

Tiny
CJ2322
  • MEMBER
  • 1999 PONTIAC GRAND AM
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 142 MILES
I have a pontiac grand am se quad 4 I have been trying to find out why I am loosing over 100 miles a tank. I replaced a faulty fuel pressure regulator, tested the coils, put in new plugs. Tried using fuel injector cleaner and also checked the air filter and a compression test. Every thing looked good with no results. I gave it to a shop and they couldn't find it. All sensors are working fine with no trouble codes or check engine lights. I'm all out of ideas.
Wednesday, April 7th, 2010 AT 2:45 PM

1 Reply

Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
I would start by measuring fuel pressure with mechanical gauge, excessive pressure will cause this.

Also look at long term fuel trim parameters in PCM, it will tell you if (over time) the PCM has been adding or removing fuel.
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Thursday, April 8th, 2010 AT 9:22 AM

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